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GLUUNPROJECT4(3G)						   OpenGL Manual						 GLUUNPROJECT4(3G)

NAME
gluUnProject4 - map window and clip coordinates to object coordinates C SPECIFICATION
GLint gluUnProject4(GLdouble winX, GLdouble winY, GLdouble winZ, GLdouble clipW, const GLdouble * model, const GLdouble * proj, const GLint * view, GLdouble nearVal, GLdouble farVal, GLdouble* objX, GLdouble* objY, GLdouble* objZ, GLdouble* objW); PARAMETERS
winX, winY, winZ Specify the window coordinates to be mapped. clipW Specify the clip w coordinate to be mapped. model Specifies the modelview matrix (as from a glGetDoublev() call). proj Specifies the projection matrix (as from a glGetDoublev() call). view Specifies the viewport (as from a glGetIntegerv() call). nearVal, farVal Specifies the near and far planes (as from a glGetDoublev() call). objX, objY, objZ, objW Returns the computed object coordinates. DESCRIPTION
gluUnProject4 maps the specified window coordinatesi: winX, winY, and winZ and its clip w coordinate clipW into object coordinates objX objY objZ objW using model, proj, and view. clipW can be other than 1 as for vertices in glFeedbackBuffer() when data type GLU_4D_COLOR_TEXTURE is returned. This also handles the case where the nearVal and farVal planes are different from the default, 0 and 1, respectively. A return value of GLU_TRUE indicates success; a return value of GLU_FALSE indicates failure. To compute the coordinates objX objY objZ objW, gluUnProject4 multiplies the normalized device coordinates by the inverse of model * proj as follows: objX objY objZ objW = INV P M 2 winX - view 0 view 2 - 1 2 winY - view 1 view 3 - 1 2 winZ - nearVal farVal - nearVal - 1 clipW INV denotes matrix inversion. gluUnProject4 is equivalent to gluUnProject() when clipW is 1, nearVal is 0, and farVal is 1. NOTES
gluUnProject4 is available only if the GLU version is 1.3 or greater. SEE ALSO
gluProject(), gluUnProject(), glFeedbackBuffer(), glGet() 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 GLUUNPROJECT4(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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