1991-2006
Silicon Graphics, Inc.
2011-2013
Khronos Group
glEnable
3G

# glEnable

enable or disable server-side GL capabilities

## C Specification

                    void glEnable
                    GLenum cap

                    void glDisable
                    GLenum cap

                    void glEnablei
                    GLenum cap
                    GLuint index

                    void glDisablei
                    GLenum cap
                    GLuint index

## Parameters

`cap`

  Specifies a symbolic constant indicating a GL capability.

`index`

  Specifies the index of the switch to disable (for `glEnablei` and `glDisablei` only).

## Description

`glEnable` and `glDisable` enable and disable various capabilities. Use glIsEnabled or glGet to determine the current setting of any capability. The initial value for each capability with the exception of `GL_DITHER` and `GL_MULTISAMPLE` is `GL_FALSE`. The initial value for `GL_DITHER` and `GL_MULTISAMPLE` is `GL_TRUE`.

Both `glEnable` and `glDisable` take a single argument, `cap`, which can assume one of the following values:

Some of the GL's capabilities are indexed. `glEnablei` and `glDisablei` enable and disable indexed capabilities.

`GL_BLEND`

  If enabled, blend the computed fragment color values with the values in the color buffers. See glBlendFunc.

`GL_CLIP_DISTANCE` i

  If enabled, clip geometry against user-defined half space i.

`GL_COLOR_LOGIC_OP`

  If enabled, apply the currently selected logical operation to the computed fragment color and color buffer values. See glLogicOp.

`GL_CULL_FACE`

  If enabled, cull polygons based on their winding in window coordinates. See glCullFace.

`GL_DEBUG_OUTPUT`

  If enabled, debug messages are produced by a debug context. When disabled, the debug message log is silenced. Note that in a non-debug context, very few, if any messages might be produced, even when `GL_DEBUG_OUTPUT` is enabled.

`GL_DEBUG_OUTPUT_SYNCHRONOUS`

  If enabled, debug messages are produced synchronously by a debug context. If disabled, debug messages may be produced asynchronously. In particular, they may be delayed relative to the execution of GL commands, and the debug callback function may be called from a thread other than that in which the commands are executed. See glDebugMessageCallback.

`GL_DEPTH_CLAMP`

  If enabled, the -wc≤zc≤wc plane equation is ignored by view volume clipping (effectively, there is no near or far plane clipping). See glDepthRange.

`GL_DEPTH_TEST`

  If enabled, do depth comparisons and update the depth buffer. Note that even if the depth buffer exists and the depth mask is non-zero, the depth buffer is not updated if the depth test is disabled. See glDepthFunc and glDepthRange.

`GL_DITHER`

  If enabled, dither color components or indices before they are written to the color buffer.

`GL_FRAMEBUFFER_SRGB`

  If enabled and the value of `GL_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING` for the framebuffer attachment corresponding to the destination buffer is `GL_SRGB`, the R, G, and B destination color values (after conversion from fixed-point to floating-point) are considered to be encoded for the sRGB color space and hence are linearized prior to their use in blending.

`GL_LINE_SMOOTH`

  If enabled, draw lines with correct filtering. Otherwise, draw aliased lines. See glLineWidth.

`GL_MULTISAMPLE`

  If enabled, use multiple fragment samples in computing the final color of a pixel. See glSampleCoverage.

`GL_POLYGON_OFFSET_FILL`

  If enabled, and if the polygon is rendered in `GL_FILL` mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset.

`GL_POLYGON_OFFSET_LINE`

  If enabled, and if the polygon is rendered in `GL_LINE` mode, an offset is added to depth values of a polygon's fragments before the depth comparison is performed. See glPolygonOffset.

`GL_POLYGON_OFFSET_POINT`

  If enabled, an offset is added to depth values of a polygon's fragments before the depth comparison is performed, if the polygon is rendered in `GL_POINT` mode. See glPolygonOffset.

`GL_POLYGON_SMOOTH`

  If enabled, draw polygons with proper filtering. Otherwise, draw aliased polygons. For correct antialiased polygons, an alpha buffer is needed and the polygons must be sorted front to back.

`GL_PRIMITIVE_RESTART`

  Enables primitive restarting. If enabled, any one of the draw commands which transfers a set of generic attribute array elements to the GL will restart the primitive when the index of the vertex is equal to the primitive restart index. See glPrimitiveRestartIndex.

`GL_PRIMITIVE_RESTART_FIXED_INDEX`

  Enables primitive restarting with a fixed index. If enabled, any one of the draw commands which transfers a set of generic attribute array elements to the GL will restart the primitive when the index of the vertex is equal to the fixed primitive index for the specified index type. The fixed index is equal to 2 n−1 where n is equal to 8 for `GL_UNSIGNED_BYTE`, 16 for `GL_UNSIGNED_SHORT` and 32 for `GL_UNSIGNED_INT`.

`GL_RASTERIZER_DISCARD`

  If enabled, primitives are discarded after the optional transform feedback stage, but before rasterization. Furthermore, when enabled, glClear, glClearBufferData, glClearBufferSubData, glClearTexImage, and glClearTexSubImage are ignored.

`GL_SAMPLE_ALPHA_TO_COVERAGE`

  If enabled, compute a temporary coverage value where each bit is determined by the alpha value at the corresponding sample location. The temporary coverage value is then ANDed with the fragment coverage value.

`GL_SAMPLE_ALPHA_TO_ONE`

  If enabled, each sample alpha value is replaced by the maximum representable alpha value.

`GL_SAMPLE_COVERAGE`

  If enabled, the fragment's coverage is ANDed with the temporary coverage value. If `GL_SAMPLE_COVERAGE_INVERT` is set to `GL_TRUE`, invert the coverage value. See glSampleCoverage.

`GL_SAMPLE_SHADING`

  If enabled, the active fragment shader is run once for each covered sample, or at fraction of this rate as determined by the current value of `GL_MIN_SAMPLE_SHADING_VALUE`. See glMinSampleShading.

`GL_SAMPLE_MASK`

  If enabled, the sample coverage mask generated for a fragment during rasterization will be ANDed with the value of `GL_SAMPLE_MASK_VALUE` before shading occurs. See glSampleMaski.

`GL_SCISSOR_TEST`

  If enabled, discard fragments that are outside the scissor rectangle. See glScissor.

`GL_STENCIL_TEST`

  If enabled, do stencil testing and update the stencil buffer. See glStencilFunc and glStencilOp.

`GL_TEXTURE_CUBE_MAP_SEAMLESS`

  If enabled, cubemap textures are sampled such that when linearly sampling from the border between two adjacent faces, texels from both faces are used to generate the final sample value. When disabled, texels from only a single face are used to construct the final sample value.

`GL_PROGRAM_POINT_SIZE`

  If enabled and a vertex or geometry shader is active, then the derived point size is taken from the (potentially clipped) shader builtin `gl_PointSize` and clamped to the implementation-dependent point size range.

## Errors

`GL_INVALID_ENUM` is generated if `cap` is not one of the values listed previously.

`GL_INVALID_VALUE` is generated by `glEnablei` and `glDisablei` if `index` is greater than or equal to the number of indexed capabilities for `cap`.

## Notes

`GL_PRIMITIVE_RESTART` is available only if the GL version is 3.1 or greater.

`GL_TEXTURE_CUBE_MAP_SEAMLESS` is available only if the GL version is 3.2 or greater.

`GL_PRIMITIVE_RESTART_FIXED_INDEX` is available only if the GL version is 4.3 or greater.

`GL_DEBUG_OUTPUT` and `GL_DEBUG_OUTPUT_SYNCHRONOUS` are available only if the GL version is 4.3 or greater.

Any token accepted by `glEnable` or `glDisable` is also accepted by `glEnablei` and `glDisablei`, but if the capability is not indexed, the maximum value that `index` may take is zero.

In general, passing an indexed capability to `glEnable` or `glDisable` will enable or disable that capability for all indices, resepectively.

## Associated Gets

glIsEnabled

glGet

## See Also

glActiveTexture, glBlendFunc, glCullFace, glDepthFunc, glDepthRange, glGet, glIsEnabled, glLineWidth, glLogicOp, glPointSize, glPolygonMode, glPolygonOffset, glSampleCoverage, glScissor, glStencilFunc, glStencilOp, glTexImage1D, glTexImage2D, glTexImage3D

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2011-2013 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.