Index for Section 3G

Alphabetical listing for G

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glFrustum(3G)
NAME
  glFrustum - multiply the current matrix by a perspective matrix

SYNOPSIS
  void glFrustum(
	  GLdouble left,
	  GLdouble right,
	  GLdouble bottom,
	  GLdouble top,
	  GLdouble zNear,
	  GLdouble zFar );

PARAMETERS
  left, right
      Specify the coordinates for the left and right vertical clipping
      planes.

  bottom, top
      Specify the coordinates for the bottom and top horizontal clipping
      planes.

  zNear, zFar
      Specify the distances to the near and far depth clipping planes.	Both
      distances must be positive.

DESCRIPTION
  glFrustum() describes a perspective matrix that produces a perspective
  projection. The current matrix (see glMatrixMode()) is multiplied by this
  matrix and the result replaces the current matrix, as if glMultMatrix()
  were called with the following matrix as its argument:

       {2 zNear} / {right - left}	  0				   A  0
	 0			  {2 zNear} / {top - bottom}		   B  0
	 0				     0				   C  D
	 0				     0				  -1  0
				  A = {right + left} / {right - left}
				  B = {top + bottom} / {top - bottom}
				  C = -{zFar + zNear} / {zFar - zNear}
				  D = -{2 zFar zNear} / {zFar - zNear}

  Typically, the matrix mode is GL_PROJECTION, and (left, bottom, -zNear) and
  (right, top,	-zNear) specify the points on the near clipping plane that
  are mapped to the lower left and upper right corners of the window,
  assuming that the eye is located at (0, 0, 0). -zFar specifies the location
  of the far clipping plane. Both zNear and zFar must be positive.

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

ERRORS
  GL_INVALID_VALUE is generated if zNear or zFar is not positive, or if left
  = right, or bottom = top.

  GL_INVALID_OPERATION is generated if glFrustum() is executed between the
  execution of glBegin() and the corresponding execution of glEnd().

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
       glGet() with argument GL_COLOR_MATRIX

SEE ALSO
  glOrtho(3), glMatrixMode(3), glMultMatrix(3), glPushMatrix(3),
  glViewport(3)

Index for Section 3G

Alphabetical listing for G

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