HP b2600 Reference Manual page 160

F
glFrustum
Use glPushMatrix and glPopMatrix to save and restore the current matrix stack.
Notes
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 log
zNear approaches 0, zNear must never be set to 0.
Errors
•
•
Associated Gets
glGet with argument GL_MATRIX_MODE
glGet with argument GL_MODELVIEW_MATRIX
glGet with argument GL_PROJECTION_MATRIX
glGet with argument GL_TEXTURE_MATRIX
See Also
glOrtho,
glMatrixMode,
glMultMatrix,
glPushMatrix
glViewport
160
r bits of depth-buffer precision are lost. Because r approaches infinity as
2
GL_INVALID_VALUE is generated if zNear or zFar is not positive.
GL_INVALID_OPERATION is generated if glFrustum is executed between the
execution of glBegin and the corresponding execution of glEnd.
Chapter 6