GLUUNPROJECT4

Section: Misc. Reference Manual Pages (3G)
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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 near,
                       GLdouble far,
                       GLdouble* objX,
                       GLdouble* objY,
                       GLdouble* objZ,
                       GLdouble* objW )

delim $$

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).
near, far: 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 coordinates 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 GL_4D_COLOR_TEXTURE is returned. This also handles the case where the near and far planes are different from the default, 0 and 1, respectively. A return value of GL_TRUE indicates success; a return value of GL_FALSE indicates failure.

To compute the coordinates (objX, objY, objZ and objW), gluUnProject4 multiplies the normalized device coordinates by the inverse of model*proj as follows:

left ( down 70 {cpile { ~"objX" above ~"objY" above ~"objZ" above ~"objW"}} ~~ right ) ~=~ INV(P M) left ( down 140 {cpile { { {2("winX" ~-~ "view"[0])} over {"view"[2]} ~-~ 1 } above { {2("winY" ~-~ "view"[1])} over {"view"[3]} ~-~ 1 } above { {2("winZ" ~-~ "near")} over {("far" ~-~ "near")} ~-~ 1 } above "clipW"}} ~~ right )

$INV()$ denotes matrix inversion.

gluUnProject4 is equivalent to gluUnProject when clipW is 1, near is 0 and far is 1.

NOTES

gluUnProject4 is available only if the GLU version is 1.3 or greater.