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gluUnProject

Chapter 19

468

gluUnProject

gluUnProject: map window coordinates to object coordinates.

C Speciﬁcation

GLint gluUnProject(

GLdouble winX,

GLdouble winY,

GLdouble winZ,

const GLdouble *model,

const GLdouble *proj,

const GLint *view,

GLdouble* objX,

GLdouble* objY,

GLdouble* objZ)

Parameters

winX, winY, winZ Specify the window coordinates 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).

objX, objY, objZ Returns the computed object coordinates.

Description

gluUnProject maps the speciﬁed window coordinates into object coordinates using

model, proj, and view. The result is stored in objX, objY, and objZ. A return value of

GL_TRUE indicates success; a return value of GL_FALSE indicates failure.

To compute the coordinates (objX, objY, objZ), gluUnProject multiplies the normalized

device coordinates by the inverse of model × proj as follows:

objX 2 (winX - view[0] ) / view[2]

objY = INV(PM ) - 1

objZ 2 (winY - view[1] ) / view[3]

W- 1

2 winZ - 1

“INV()” denotes matrix inversion. W is an unused variable, included for consistent

matrix notation.

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