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GLCLIPPLANE(3G) 						   OpenGL Manual						   GLCLIPPLANE(3G)

NAME
glClipPlane - specify a plane against which all geometry is clipped C SPECIFICATION
void glClipPlane(GLenum plane, const GLdouble * equation); PARAMETERS
plane Specifies which clipping plane is being positioned. Symbolic names of the form GL_CLIP_PLANEi, where i is an integer between 0 and GL_MAX_CLIP_PLANES-1, are accepted. equation Specifies the address of an array of four double-precision floating-point values. These values are interpreted as a plane equation. DESCRIPTION
Geometry is always clipped against the boundaries of a six-plane frustum in x, y, and z. glClipPlane allows the specification of additional planes, not necessarily perpendicular to the x, y, or z axis, against which all geometry is clipped. To determine the maximum number of additional clipping planes, call glGetIntegerv() with argument GL_MAX_CLIP_PLANES. All implementations support at least six such clipping planes. Because the resulting clipping region is the intersection of the defined half-spaces, it is always convex. glClipPlane specifies a half-space using a four-component plane equation. When glClipPlane is called, equation is transformed by the inverse of the modelview matrix and stored in the resulting eye coordinates. Subsequent changes to the modelview matrix have no effect on the stored plane-equation components. If the dot product of the eye coordinates of a vertex with the stored plane equation components is positive or zero, the vertex is in with respect to that clipping plane. Otherwise, it is out. To enable and disable clipping planes, call glEnable() and glDisable() with the argument GL_CLIP_PLANEi, where i is the plane number. All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates and are disabled. NOTES
It is always the case that GL_CLIP_PLANEi = GL_CLIP_PLANE0 + i. ERRORS
GL_INVALID_ENUM is generated if plane is not an accepted value. GL_INVALID_OPERATION is generated if glClipPlane is executed between the execution of glBegin() and the corresponding execution of glEnd(). ASSOCIATED GETS
glGetClipPlane() glIsEnabled() with argument GL_CLIP_PLANEi SEE ALSO
glEnable() COPYRIGHT
Copyright (C) 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/. AUTHORS
opengl.org opengl.org 06/10/2014 GLCLIPPLANE(3G)

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GLFRUSTUM(3G)							   OpenGL Manual						     GLFRUSTUM(3G)

NAME
glFrustum - multiply the current matrix by a perspective matrix C SPECIFICATION
void glFrustum(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble nearVal, GLdouble farVal); 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. nearVal, farVal 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 nearVal right - left 0 A 0 0 2 nearVal top - bottom B 0 0 0 C D 0 0 -1 0 A = right + left right - left B = top + bottom top - bottom C = - farVal + nearVal farVal - nearVal D = - 2 farVal nearVal farVal - nearVal Typically, the matrix mode is GL_PROJECTION, and left bottom - nearVal and right top - nearVal 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). - farVal specifies the location of the far clipping plane. Both nearVal and farVal 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 nearVal and farVal. The greater the ratio of farVal to nearVal is, the less effective the depth buffer will be at distinguishing between surfaces that are near each other. If r = farVal nearVal roughly log 2 r bits of depth buffer precision are lost. Because r approaches infinity as nearVal approaches 0, nearVal must never be set to 0. ERRORS
GL_INVALID_VALUE is generated if nearVal or farVal is not positive, or if left = right, or bottom = top, or near = far. 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(), glMatrixMode(), glMultMatrix(), glPushMatrix(), glViewport() COPYRIGHT
Copyright (C) 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/. AUTHORS
opengl.org opengl.org 06/10/2014 GLFRUSTUM(3G)
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