1991-2006
Silicon Graphics, Inc.
gluLookAt
3G

# gluLookAt

define a viewing transformation

## C Specification

                    void gluLookAt
                    GLdouble eyeX
                    GLdouble eyeY
                    GLdouble eyeZ
                    GLdouble centerX
                    GLdouble centerY
                    GLdouble centerZ
                    GLdouble upX
                    GLdouble upY
                    GLdouble upZ

## Parameters

`eyeX`
`eyeY`
`eyeZ`

  Specifies the position of the eye point.

`centerX`
`centerY`
`centerZ`

  Specifies the position of the reference point.

`upX`
`upY`
`upZ`

  Specifies the direction of the up vector.

## Description

`gluLookAt` creates a viewing matrix derived from an eye point, a reference point indicating the center of the scene, and an UP vector.

The matrix maps the reference point to the negative z axis and the eye point to the origin. When a typical projection matrix is used, the center of the scene therefore maps to the center of the viewport. Similarly, the direction described by the UP vector projected onto the viewing plane is mapped to the positive y axis so that it points upward in the viewport. The UP vector must not be parallel to the line of sight from the eye point to the reference point.

Let

F = centerX - eyeX centerY - eyeY centerZ - eyeZ

Let UP be the vector upX upY upZ .

Then normalize as follows: f = F F

UP ″ = UP UP

Finally, let s = f × UP ″ , and u = s × f .

M is then constructed as follows: M = s &af; 0 s &af; 1 s &af; 2 0 u &af; 0 u &af; 1 u &af; 2 0 - f &af; 0 - f &af; 1 - f &af; 2 0 0 0 0 1

and `gluLookAt` is equivalent to

    glMultMatrixf(M);
    glTranslated(-eyex, -eyey, -eyez);

## See Also

gluPerspective, glFrustum

## Copyright

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