Sets up a perspective projection matrix.
OpenGL C bindings library: libGL.a
void gluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)
The gluPerspective subroutine specifies a viewing frustum into the world coordinate system. Generally, the aspect used with this subroutine should match that of its associated viewport. For example, an aspect ratio value of aspect=2.0 means the viewer's angle of view is twice as wide in x as it is in y. If the viewport is twice as wide as it is tall, it displays the image without distortion.
The matrix generated by the gluPerspective subroutine is multiplied by the current matrix just as if the glMultMatrix subroutine were called with the generated matrix. To load the perspective matrix onto the current matrix stack instead, precede the call to gluPerspective with a call to the glLoadIdentity subroutine.
Given f defined as follows:
f = cotangent(fovy/2)
The generated matrix is
( f )
| ------ 0 0 0 |
| aspect |
| |
| |
| 0 f 0 0 |
| |
| |
| zFar+zNear 2*zFar*zNear |
| 0 0 ---------- ------------ |
| zNear-zFar zNear-zFar |
| |
| |
| 0 0 -1 0 |
( )
Depth buffer precision is affected by the values specified for zNear and zFar. The greater the ratio of zFar to zNear is, the less effective the depth buffer will be at distinguishing between surfaces that are near each other. If
r = zFar/zNear
roughly log2(r) bits of depth buffer precision are lost. Because r approaches infinity as zNear approaches 0, zNear must never be set to 0.
| /usr/include/GL/gl.h | Contains C language constraints, variable type definitions, and ANSI function prototypes for OpenGL. |
The glFrustum subroutine, glLoadIdentity subroutine, glMultMatrix subroutine, gluOrtho2D subroutine.