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 © 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/.