Tao.OpenGl SDK Documentation

Glu.gluPerspective Method 

Sets up a perspective projection matrix.

[Visual Basic]
Public Shared Sub gluPerspective( _
   ByVal fovY As Double, _
   ByVal aspectRatio As Double, _
   ByVal zNear As Double, _
   ByVal zFar As Double _
)
[C#]
public static void gluPerspective(
   double fovY,
   double aspectRatio,
   double zNear,
   double zFar
);

Parameters

fovY
The field of view angle, in degrees, in the y-direction.
aspectRatio
The aspect ratio that determines the field of view in the x-direction. The aspect ratio is the ratio of x (width) to y (height).
zNear
The distance from the viewer to the near clipping plane (always positive).
zFar
The distance from the viewer to the far clipping plane (always positive).

Remarks

The gluPerspective subroutine specifies a viewing frustum into the world coordinate system. Generally, the aspect ratio 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 gluPerspective is multipled by the current matrix, just as if Gl.glMultMatrix* 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 glLoadIdentity.

Given f defined as follows:

f = cotangent(fovY / 2)

The generated matrix is:

            (     f                                       )
            |  ------        0       0            0       |
            |  aspectRatio                                |
            |                                             |
            |                                             |
            |     0          f       0            0       |
            |                                             |
            |                                             |
            |                    zFar+zNear  2*zFar*zNear |
            |     0          0   ----------  ------------ |
            |                    zNear-zFar   zNear-zFar  |
            |                                             |
            |                                             |
            |     0          0      -1            0       |
            (                                             )
            

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 log2(r) bits of depth buffer precision are lost. Because r approaches infinity as zNear approaches 0, zNear must never be set to 0.

See Also

Glu Class | Tao.OpenGl Namespace | glFrustum | glLoadIdentity | gluOrtho2D