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1236 lines
69 KiB
XML
1236 lines
69 KiB
XML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glDrawPixels">
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<refmeta>
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<refmetainfo>
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<copyright>
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<year>1991-2006</year>
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<holder>Silicon Graphics, Inc.</holder>
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</copyright>
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</refmetainfo>
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<refentrytitle>glDrawPixels</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glDrawPixels</refname>
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<refpurpose>write a block of pixels to the frame buffer</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glDrawPixels</function></funcdef>
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<paramdef>GLsizei <parameter>width</parameter></paramdef>
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<paramdef>GLsizei <parameter>height</parameter></paramdef>
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<paramdef>GLenum <parameter>format</parameter></paramdef>
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<paramdef>GLenum <parameter>type</parameter></paramdef>
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<paramdef>const GLvoid * <parameter>data</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<!-- eqn: ignoring delim $$ -->
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>width</parameter></term>
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<term><parameter>height</parameter></term>
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<listitem>
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<para>
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Specify the dimensions of the pixel rectangle to be written
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into the frame buffer.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>format</parameter></term>
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<listitem>
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<para>
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Specifies the format of the pixel data.
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Symbolic constants
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<constant>GL_COLOR_INDEX</constant>,
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<constant>GL_STENCIL_INDEX</constant>,
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<constant>GL_DEPTH_COMPONENT</constant>,
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<constant>GL_RGB</constant>,
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<constant>GL_BGR</constant>,
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<constant>GL_RGBA</constant>,
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<constant>GL_BGRA</constant>,
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<constant>GL_RED</constant>,
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<constant>GL_GREEN</constant>,
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<constant>GL_BLUE</constant>,
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<constant>GL_ALPHA</constant>,
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<constant>GL_LUMINANCE</constant>, and
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<constant>GL_LUMINANCE_ALPHA</constant> are accepted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>type</parameter></term>
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<listitem>
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<para>
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Specifies the data type for <parameter>data</parameter>.
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Symbolic constants
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<constant>GL_UNSIGNED_BYTE</constant>,
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<constant>GL_BYTE</constant>,
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<constant>GL_BITMAP</constant>,
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<constant>GL_UNSIGNED_SHORT</constant>,
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<constant>GL_SHORT</constant>,
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<constant>GL_UNSIGNED_INT</constant>,
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<constant>GL_INT</constant>,
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<constant>GL_FLOAT</constant>,
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<constant>GL_UNSIGNED_BYTE_3_3_2</constant>,
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<constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,
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<constant>GL_UNSIGNED_SHORT_5_6_5</constant>,
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<constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>,
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<constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,
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<constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
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<constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>,
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<constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>,
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<constant>GL_UNSIGNED_INT_8_8_8_8</constant>,
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<constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>,
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<constant>GL_UNSIGNED_INT_10_10_10_2</constant>, and
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<constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>
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are accepted.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>data</parameter></term>
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<listitem>
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<para>
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Specifies a pointer to the pixel data.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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<function>glDrawPixels</function> reads pixel data from memory and writes it into the frame buffer
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relative to the current raster position, provided that the raster
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position is valid. Use
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<citerefentry><refentrytitle>glRasterPos</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glWindowPos</refentrytitle></citerefentry> to set the current raster position; use
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_CURRENT_RASTER_POSITION_VALID</constant>
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to determine if the specified raster position is valid, and
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_CURRENT_RASTER_POSITION</constant>
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to query the raster position.
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</para>
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<para>
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Several parameters define the encoding of pixel data in memory
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and control the processing of the pixel data
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before it is placed in the frame buffer.
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These parameters are set with four commands:
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<citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glPixelMap</refentrytitle></citerefentry>, and <citerefentry><refentrytitle>glPixelZoom</refentrytitle></citerefentry>.
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This reference page describes the effects on <function>glDrawPixels</function> of many,
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but not all, of the parameters specified by these four commands.
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</para>
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<para>
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Data is read from <parameter>data</parameter> as a sequence of signed or unsigned bytes,
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signed or unsigned shorts, signed or unsigned integers, or
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single-precision floating-point values, depending on <parameter>type</parameter>.
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When <parameter>type</parameter> is one of <constant>GL_UNSIGNED_BYTE</constant>, <constant>GL_BYTE</constant>,
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<constant>GL_UNSIGNED_SHORT</constant>, <constant>GL_SHORT</constant>, <constant>GL_UNSIGNED_INT</constant>,
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<constant>GL_INT</constant>, or <constant>GL_FLOAT</constant> each of these bytes, shorts, integers, or
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floating-point values is interpreted as one color or depth component, or
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one index, depending on <parameter>format</parameter>.
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When <parameter>type</parameter> is one of <constant>GL_UNSIGNED_BYTE_3_3_2</constant>,
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<constant>GL_UNSIGNED_SHORT_5_6_5</constant>, <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,
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<constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>, <constant>GL_UNSIGNED_INT_8_8_8_8</constant>, or
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<constant>GL_UNSIGNED_INT_10_10_10_2</constant>, each unsigned value is interpreted as
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containing all the components for a single pixel, with the color
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components arranged according to <parameter>format</parameter>.
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When <parameter>type</parameter> is one of <constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,
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<constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>, <constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
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<constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>, <constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>, or
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<constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>, each unsigned value is interpreted
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as containing all color components, specified by <parameter>format</parameter>, for a single
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pixel in a reversed order. Indices are always treated individually.
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Color components are treated as groups of one, two, three, or four
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values, again based on <parameter>format</parameter>. Both individual indices and groups of
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components are referred to as pixels.
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If <parameter>type</parameter> is <constant>GL_BITMAP</constant>, the data must be unsigned bytes, and
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<parameter>format</parameter> must be either <constant>GL_COLOR_INDEX</constant> or <constant>GL_STENCIL_INDEX</constant>.
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Each unsigned byte is treated as eight 1-bit pixels, with bit ordering
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determined by <constant>GL_UNPACK_LSB_FIRST</constant> (see <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>).
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</para>
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<para>
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<inlineequation><mml:math>
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<!-- eqn: width times height:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">width</mml:mi>
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<mml:mo>×</mml:mo>
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<mml:mi mathvariant="italic">height</mml:mi>
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</mml:mrow>
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</mml:math></inlineequation>
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pixels are read from memory,
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starting at location <parameter>data</parameter>.
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By default, these pixels are taken from adjacent memory locations,
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except that after all <parameter>width</parameter> pixels are read,
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the read pointer is advanced to the next four-byte boundary.
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The four-byte row alignment is specified by <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry> with
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argument <constant>GL_UNPACK_ALIGNMENT</constant>,
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and it can be set to one, two, four, or eight bytes.
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Other pixel store parameters specify different read pointer advancements,
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both before the first pixel is read
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and after all <parameter>width</parameter> pixels are read.
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See the <citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry> reference page for details on these options.
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</para>
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<para>
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If a non-zero named buffer object is bound to the <constant>GL_PIXEL_UNPACK_BUFFER</constant> target
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(see <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>) while a block of pixels is
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specified, <parameter>data</parameter> is treated as a byte offset into the buffer object's data store.
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</para>
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<para>
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The
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<inlineequation><mml:math>
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<!-- eqn: width times height:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">width</mml:mi>
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<mml:mo>×</mml:mo>
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<mml:mi mathvariant="italic">height</mml:mi>
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</mml:mrow>
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</mml:math></inlineequation>
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pixels that are read from memory are
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each operated on in the same way,
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based on the values of several parameters specified by <citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>
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and <citerefentry><refentrytitle>glPixelMap</refentrytitle></citerefentry>.
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The details of these operations,
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as well as the target buffer into which the pixels are drawn,
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are specific to the format of the pixels,
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as specified by <parameter>format</parameter>.
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<parameter>format</parameter> can assume one of 13 symbolic values:
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</para>
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<variablelist>
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<varlistentry>
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<term><constant>GL_COLOR_INDEX</constant></term>
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<listitem>
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<para>
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Each pixel is a single value,
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a color index.
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It is converted to fixed-point format,
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with an unspecified number of bits to the right of the binary point,
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regardless of the memory data type.
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Floating-point values convert to true fixed-point values.
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Signed and unsigned integer data is converted with all fraction bits
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set to 0.
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Bitmap data convert to either 0 or 1.
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</para>
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<para>
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Each fixed-point index is then shifted left by <constant>GL_INDEX_SHIFT</constant> bits
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and added to <constant>GL_INDEX_OFFSET</constant>.
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If <constant>GL_INDEX_SHIFT</constant> is negative,
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the shift is to the right.
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In either case, zero bits fill otherwise unspecified bit locations in the
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result.
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</para>
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<para>
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If the GL is in RGBA mode,
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the resulting index is converted to an RGBA pixel
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with the help of the <constant>GL_PIXEL_MAP_I_TO_R</constant>,
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<constant>GL_PIXEL_MAP_I_TO_G</constant>,
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<constant>GL_PIXEL_MAP_I_TO_B</constant>,
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and <constant>GL_PIXEL_MAP_I_TO_A</constant> tables.
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If the GL is in color index mode,
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and if <constant>GL_MAP_COLOR</constant> is true,
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the index is replaced with the value that it references in lookup table
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<constant>GL_PIXEL_MAP_I_TO_I</constant>.
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Whether the lookup replacement of the index is done or not,
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the integer part of the index is then ANDed with
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<inlineequation><mml:math>
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<!-- eqn: 2 sup b -1:-->
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<mml:mrow>
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<mml:msup><mml:mn>2</mml:mn>
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<mml:mi mathvariant="italic">b</mml:mi>
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</mml:msup>
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<mml:mo>-</mml:mo>
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<mml:mn>1</mml:mn>
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</mml:mrow>
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</mml:math></inlineequation>,
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where
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<inlineequation><mml:math><mml:mi mathvariant="italic">b</mml:mi></mml:math></inlineequation>
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is the number of bits in a color index buffer.
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</para>
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<para>
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The GL then converts the resulting indices or RGBA colors to fragments
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by attaching the current raster position <emphasis>z</emphasis> coordinate and
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texture coordinates to each pixel,
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then assigning
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<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
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and
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<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
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window coordinates to the
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<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
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fragment such that
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<informalequation><mml:math>
|
||
|
|
<!-- eqn: x sub n = x sub r + n mod width:-->
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||
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<mml:mrow>
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||
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<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
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<mml:mi mathvariant="italic">n</mml:mi>
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</mml:msub>
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<mml:mo>=</mml:mo>
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<mml:mrow>
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||
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<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
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<mml:mi mathvariant="italic">r</mml:mi>
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||
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</mml:msub>
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||
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<mml:mo>+</mml:mo>
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<mml:mrow>
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||
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<mml:mi mathvariant="italic">n</mml:mi>
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||
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<mml:mo>%</mml:mo>
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||
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<mml:mi mathvariant="italic">width</mml:mi>
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||
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</mml:mrow>
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||
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</mml:mrow>
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||
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</mml:mrow>
|
||
|
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</mml:math></informalequation>
|
||
|
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<para>
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||
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<informalequation><mml:math>
|
||
|
|
<!-- eqn: y sub n = y sub r + \(lf n / width \(rf:-->
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||
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<mml:mrow>
|
||
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<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
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<mml:mi mathvariant="italic">n</mml:mi>
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</mml:msub>
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||
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<mml:mo>=</mml:mo>
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
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<mml:mi mathvariant="italic">r</mml:mi>
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</mml:msub>
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||
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<mml:mo>+</mml:mo>
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||
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<mml:mfenced open="⌊" close="⌋">
|
||
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<mml:mfrac>
|
||
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<mml:mi mathvariant="italic">n</mml:mi>
|
||
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<mml:mi mathvariant="italic">width</mml:mi>
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</mml:mfrac>
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||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
</para>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: (x sub r , y sub r):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the current raster position.
|
||
|
|
These pixel fragments are then treated just like the fragments generated by
|
||
|
|
rasterizing points, lines, or polygons.
|
||
|
|
Texture mapping,
|
||
|
|
fog,
|
||
|
|
and all the fragment operations are applied before the fragments are written
|
||
|
|
to the frame buffer.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_STENCIL_INDEX</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single value,
|
||
|
|
a stencil index.
|
||
|
|
It is converted to fixed-point format,
|
||
|
|
with an unspecified number of bits to the right of the binary point,
|
||
|
|
regardless of the memory data type.
|
||
|
|
Floating-point values convert to true fixed-point values.
|
||
|
|
Signed and unsigned integer data is converted with all fraction bits
|
||
|
|
set to 0.
|
||
|
|
Bitmap data convert to either 0 or 1.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
Each fixed-point index is then shifted left by <constant>GL_INDEX_SHIFT</constant> bits,
|
||
|
|
and added to <constant>GL_INDEX_OFFSET</constant>.
|
||
|
|
If <constant>GL_INDEX_SHIFT</constant> is negative,
|
||
|
|
the shift is to the right.
|
||
|
|
In either case, zero bits fill otherwise unspecified bit locations in the
|
||
|
|
result.
|
||
|
|
If <constant>GL_MAP_STENCIL</constant> is true,
|
||
|
|
the index is replaced with the value that it references in lookup table
|
||
|
|
<constant>GL_PIXEL_MAP_S_TO_S</constant>.
|
||
|
|
Whether the lookup replacement of the index is done or not,
|
||
|
|
the integer part of the index is then ANDed with
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: 2 sup b -1:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mn>2</mml:mn>
|
||
|
|
<mml:mi mathvariant="italic">b</mml:mi>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>-</mml:mo>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">b</mml:mi></mml:math></inlineequation>
|
||
|
|
is the number of bits in the stencil buffer.
|
||
|
|
The resulting stencil indices are then written to the stencil buffer
|
||
|
|
such that the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
|
||
|
|
index is written to location
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: x sub n = x sub r + n mod width:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>%</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: y sub n = y sub r + \(lf n / width \(rf:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mfenced open="⌊" close="⌋">
|
||
|
|
<mml:mfrac>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mfrac>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: (x sub r , y sub r):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the current raster position.
|
||
|
|
Only the pixel ownership test,
|
||
|
|
the scissor test,
|
||
|
|
and the stencil writemask affect these write operations.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_DEPTH_COMPONENT</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single-depth component.
|
||
|
|
Floating-point data is converted directly to an internal floating-point
|
||
|
|
format with unspecified precision.
|
||
|
|
Signed integer data is mapped linearly to the internal floating-point
|
||
|
|
format such that the most positive representable integer value maps to 1.0,
|
||
|
|
and the most negative representable value maps to
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: -1.0:-->
|
||
|
|
<mml:mn>-1.0</mml:mn>
|
||
|
|
</mml:math></inlineequation>.
|
||
|
|
Unsigned integer data is mapped similarly:
|
||
|
|
the largest integer value maps to 1.0,
|
||
|
|
and 0 maps to 0.0.
|
||
|
|
The resulting floating-point depth value is then multiplied
|
||
|
|
by <constant>GL_DEPTH_SCALE</constant> and added to <constant>GL_DEPTH_BIAS</constant>.
|
||
|
|
The result is clamped to the range
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: [0,1]:-->
|
||
|
|
<mml:mfenced open="[" close="]">
|
||
|
|
<mml:mn>0</mml:mn>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
The GL then converts the resulting depth components to fragments
|
||
|
|
by attaching the current raster position color or color index and
|
||
|
|
texture coordinates to each pixel,
|
||
|
|
then assigning
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
|
||
|
|
window coordinates to the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
|
||
|
|
fragment such that
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: x sub n = x sub r + n mod width:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>%</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: y sub n = y sub r + \(lf n / width \(rf:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mfenced open="⌊" close="⌋">
|
||
|
|
<mml:mfrac>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mfrac>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: (x sub r , y sub r):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the current raster position.
|
||
|
|
These pixel fragments are then treated just like the fragments generated by
|
||
|
|
rasterizing points, lines, or polygons.
|
||
|
|
Texture mapping,
|
||
|
|
fog,
|
||
|
|
and all the fragment operations are applied before the fragments are written
|
||
|
|
to the frame buffer.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_RGBA</constant></term>
|
||
|
|
<listitem>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_BGRA</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a four-component group: For <constant>GL_RGBA</constant>, the red
|
||
|
|
component is first, followed by green, followed by blue, followed by
|
||
|
|
alpha; for <constant>GL_BGRA</constant> the order is blue, green, red and then alpha.
|
||
|
|
Floating-point values are converted directly to an internal floating-point
|
||
|
|
format with unspecified precision.
|
||
|
|
Signed integer values are mapped linearly to the internal floating-point
|
||
|
|
format such that the most positive representable integer value maps to 1.0,
|
||
|
|
and the most negative representable value maps to
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: -1.0:-->
|
||
|
|
<mml:mn>-1.0</mml:mn>
|
||
|
|
</mml:math></inlineequation>.
|
||
|
|
(Note that
|
||
|
|
this mapping does not convert 0 precisely to 0.0.)
|
||
|
|
Unsigned integer data is mapped similarly:
|
||
|
|
The largest integer value maps to 1.0,
|
||
|
|
and 0 maps to 0.0.
|
||
|
|
The resulting floating-point color values are then multiplied
|
||
|
|
by <constant>GL_c_SCALE</constant> and added to <constant>GL_c_BIAS</constant>,
|
||
|
|
where <emphasis>c</emphasis> is RED, GREEN, BLUE, and ALPHA
|
||
|
|
for the respective color components.
|
||
|
|
The results are clamped to the range
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: [0,1]:-->
|
||
|
|
<mml:mfenced open="[" close="]">
|
||
|
|
<mml:mn>0</mml:mn>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
If <constant>GL_MAP_COLOR</constant> is true,
|
||
|
|
each color component is scaled by the size of lookup table
|
||
|
|
<constant>GL_PIXEL_MAP_c_TO_c</constant>,
|
||
|
|
then replaced by the value that it references in that table.
|
||
|
|
<emphasis>c</emphasis> is R, G, B, or A respectively.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
The GL then converts the resulting RGBA colors to fragments
|
||
|
|
by attaching the current raster position <emphasis>z</emphasis> coordinate and
|
||
|
|
texture coordinates to each pixel,
|
||
|
|
then assigning
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
|
||
|
|
window coordinates to the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
|
||
|
|
fragment such that
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: x sub n = x sub r + n mod width:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>%</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: y sub n = y sub r + \(lf n / width \(rf:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mfenced open="⌊" close="⌋">
|
||
|
|
<mml:mfrac>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">width</mml:mi>
|
||
|
|
</mml:mfrac>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: (x sub r , y sub r):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the current raster position.
|
||
|
|
These pixel fragments are then treated just like the fragments generated by
|
||
|
|
rasterizing points, lines, or polygons.
|
||
|
|
Texture mapping,
|
||
|
|
fog,
|
||
|
|
and all the fragment operations are applied before the fragments are written
|
||
|
|
to the frame buffer.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_RED</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single red component.
|
||
|
|
This component is converted to the internal floating-point format in
|
||
|
|
the same way the red component of an RGBA pixel is. It is
|
||
|
|
then converted to an RGBA pixel with green and blue set to 0,
|
||
|
|
and alpha set to 1.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_GREEN</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single green component.
|
||
|
|
This component is converted to the internal floating-point format in
|
||
|
|
the same way the green component of an RGBA pixel is.
|
||
|
|
It is then converted to an RGBA pixel with red and blue set to 0,
|
||
|
|
and alpha set to 1.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_BLUE</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single blue component.
|
||
|
|
This component is converted to the internal floating-point format in
|
||
|
|
the same way the blue component of an RGBA pixel is.
|
||
|
|
It is then converted to an RGBA pixel with red and green set to 0,
|
||
|
|
and alpha set to 1.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_ALPHA</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single alpha component.
|
||
|
|
This component is converted to the internal floating-point format in
|
||
|
|
the same way the alpha component of an RGBA pixel is.
|
||
|
|
It is then converted to an RGBA pixel with red, green, and blue set to 0.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_RGB</constant></term>
|
||
|
|
<listitem>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_BGR</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a three-component group:
|
||
|
|
red first, followed by green, followed by blue; for <constant>GL_BGR</constant>, the
|
||
|
|
first component is blue, followed by green and then red.
|
||
|
|
Each component is converted to the internal floating-point format in
|
||
|
|
the same way the red, green, and blue components of an RGBA pixel are.
|
||
|
|
The color triple is converted to an RGBA pixel with alpha set to 1.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_LUMINANCE</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a single luminance component.
|
||
|
|
This component is converted to the internal floating-point format in
|
||
|
|
the same way the red component of an RGBA pixel is.
|
||
|
|
It is then converted to an RGBA pixel with red, green, and blue set to the
|
||
|
|
converted luminance value,
|
||
|
|
and alpha set to 1.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
<varlistentry>
|
||
|
|
<term><constant>GL_LUMINANCE_ALPHA</constant></term>
|
||
|
|
<listitem>
|
||
|
|
<para>
|
||
|
|
Each pixel is a two-component group:
|
||
|
|
luminance first, followed by alpha.
|
||
|
|
The two components are converted to the internal floating-point format in
|
||
|
|
the same way the red component of an RGBA pixel is.
|
||
|
|
They are then converted to an RGBA pixel with red, green, and blue set to the
|
||
|
|
converted luminance value,
|
||
|
|
and alpha set to the converted alpha value.
|
||
|
|
After this conversion, the pixel is treated as if it had been read
|
||
|
|
as an RGBA pixel.
|
||
|
|
|
||
|
|
</para>
|
||
|
|
</listitem>
|
||
|
|
</varlistentry>
|
||
|
|
</variablelist>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The following table summarizes the meaning of the valid constants for the
|
||
|
|
<emphasis>type</emphasis> parameter:
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informaltable frame="topbot">
|
||
|
|
<tgroup cols="2" align="left">
|
||
|
|
<colspec colwidth="1*" />
|
||
|
|
<colspec colwidth="1*" />
|
||
|
|
<thead>
|
||
|
|
<row>
|
||
|
|
<entry rowsep="1" align="left"><emphasis role="bold">
|
||
|
|
Type
|
||
|
|
</emphasis></entry>
|
||
|
|
<entry rowsep="1" align="left"><emphasis role="bold">
|
||
|
|
Corresponding Type
|
||
|
|
</emphasis></entry>
|
||
|
|
</row>
|
||
|
|
</thead>
|
||
|
|
<tbody>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_BYTE</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 8-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_BYTE</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
signed 8-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_BITMAP</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
single bits in unsigned 8-bit integers
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_SHORT</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
signed 16-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_INT</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 32-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_INT</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
32-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_FLOAT</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
single-precision floating-point
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_BYTE_3_3_2</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 8-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 8-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 16-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 32-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 32-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_INT_10_10_10_2</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 32-bit integer
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
<row>
|
||
|
|
<entry align="left">
|
||
|
|
<constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>
|
||
|
|
</entry>
|
||
|
|
<entry align="left">
|
||
|
|
unsigned 32-bit integer with reversed component ordering
|
||
|
|
</entry>
|
||
|
|
</row>
|
||
|
|
</tbody>
|
||
|
|
</tgroup>
|
||
|
|
</informaltable>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
</para>
|
||
|
|
<!--/listitem-->
|
||
|
|
<!--/varlistentry-->
|
||
|
|
<!--/variablelist-->
|
||
|
|
<para>
|
||
|
|
The rasterization described so far assumes pixel zoom factors of 1.
|
||
|
|
If
|
||
|
|
<citerefentry><refentrytitle>glPixelZoom</refentrytitle></citerefentry> is used to change the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
|
||
|
|
pixel zoom factors,
|
||
|
|
pixels are converted to fragments as follows.
|
||
|
|
If
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: (x sub r, y sub r):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the current raster position,
|
||
|
|
and a given pixel is in the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
|
||
|
|
column and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">m</mml:mi></mml:math></inlineequation>th
|
||
|
|
row
|
||
|
|
of the pixel rectangle,
|
||
|
|
then fragments are generated for pixels whose centers are in the rectangle
|
||
|
|
with corners at
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: left ( x sub r + {zoom sub x} n, y sub r + {zoom sub y} m right ):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">m</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: left ( x sub r + {zoom sub x} (n + 1), y sub r + {zoom sub y} ( m + 1 ) right ):-->
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>⁡</mml:mo>
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">r</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>⁡</mml:mo>
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">m</mml:mi>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
where
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: zoom sub x:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the value of <constant>GL_ZOOM_X</constant> and
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: zoom sub y:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">zoom</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
is the value of <constant>GL_ZOOM_Y</constant>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="notes"><title>Notes</title>
|
||
|
|
<para>
|
||
|
|
<constant>GL_BGR</constant> and <constant>GL_BGRA</constant> are only valid for <parameter>format</parameter> if the GL
|
||
|
|
version is 1.2 or greater.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_UNSIGNED_BYTE_3_3_2</constant>,
|
||
|
|
<constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_10_10_10_2</constant>, and
|
||
|
|
<constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant> are only valid for <parameter>type</parameter> if the
|
||
|
|
GL version is 1.2 or greater.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="errors"><title>Errors</title>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>format</parameter> or <parameter>type</parameter> is not one of
|
||
|
|
the accepted values.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>type</parameter> is <constant>GL_BITMAP</constant> and
|
||
|
|
<parameter>format</parameter> is not either <constant>GL_COLOR_INDEX</constant> or <constant>GL_STENCIL_INDEX</constant>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_VALUE</constant> is generated if either <parameter>width</parameter> or <parameter>height</parameter> is negative.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>format</parameter> is <constant>GL_STENCIL_INDEX</constant>
|
||
|
|
and there is no stencil buffer.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>format</parameter> is
|
||
|
|
<constant>GL_RED</constant>,
|
||
|
|
<constant>GL_GREEN</constant>,
|
||
|
|
<constant>GL_BLUE</constant>,
|
||
|
|
<constant>GL_ALPHA</constant>,
|
||
|
|
<constant>GL_RGB</constant>,
|
||
|
|
<constant>GL_RGBA</constant>,
|
||
|
|
<constant>GL_BGR</constant>,
|
||
|
|
<constant>GL_BGRA</constant>,
|
||
|
|
<constant>GL_LUMINANCE</constant>,
|
||
|
|
or
|
||
|
|
<constant>GL_LUMINANCE_ALPHA</constant>,
|
||
|
|
and the GL is in color index mode.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>format</parameter> is one of
|
||
|
|
<constant>GL_UNSIGNED_BYTE_3_3_2</constant>,
|
||
|
|
<constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5</constant>, or
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>
|
||
|
|
and <parameter>format</parameter> is not <constant>GL_RGB</constant>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>format</parameter> is one of
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>,
|
||
|
|
<constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>,
|
||
|
|
<constant>GL_UNSIGNED_INT_10_10_10_2</constant>, or
|
||
|
|
<constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>
|
||
|
|
and <parameter>format</parameter> is neither <constant>GL_RGBA</constant> nor <constant>GL_BGRA</constant>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the
|
||
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the buffer object's data store is currently mapped.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the
|
||
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant> target and the data would be unpacked from the buffer
|
||
|
|
object such that the memory reads required would exceed the data store size.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the
|
||
|
|
<constant>GL_PIXEL_UNPACK_BUFFER</constant> target and <parameter>data</parameter> is not evenly divisible
|
||
|
|
into the number of bytes needed to store in memory a datum indicated by <parameter>type</parameter>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glDrawPixels</function>
|
||
|
|
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
|
||
|
|
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="associatedgets"><title>Associated Gets</title>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_CURRENT_RASTER_POSITION</constant>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_CURRENT_RASTER_POSITION_VALID</constant>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_PIXEL_UNPACK_BUFFER_BINDING</constant>
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="seealso"><title>See Also</title>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glPixelMap</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glPixelStore</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glPixelZoom</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glRasterPos</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glWindowPos</refentrytitle></citerefentry>
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="Copyright"><title>Copyright</title>
|
||
|
|
<para>
|
||
|
|
Copyright <trademark class="copyright"></trademark> 1991-2006
|
||
|
|
Silicon Graphics, Inc. This document is licensed under the SGI
|
||
|
|
Free Software B License. For details, see
|
||
|
|
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
</refentry>
|