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gluProject

Chapter 14

348

gluProject

gluProject: map object coordinates to window coordinates.

C Speciﬁcation

GLint gluProject(

GLdouble objX,

GLdouble objY,

GLdouble objZ,

const GLdouble *model,

const GLdouble *proj,

const GLint *view,

GLdouble* winX,

GLdouble* winY,

GLdouble* winZ)

Parameters

objA, objY, objZ Specify the object coordinates.

model Speciﬁes the current modelview matrix (as from a glGetDoublev call).

proj Speciﬁes the current projection matrix (as from a glGetDoublev call).

view Speciﬁes the current viewport (as from a glGetIntegerv call).

winX, winY, winZ Return the computed window coordinates.

Description

gluProject transforms the speciﬁed object coordinates into window coordinates using

model, proj, and view. The result is stored in winX, winY, and winZ. A return value of

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

To compute the coordinates, let v = (objX, objY, objZ, 1.0) represented as a matrix with 4

rows and 1 column. Then gluProject computes v as follows:

v = P × M × v

where P is the current projection matrix proj, M is the current modelview matrix model

(both represented as 4 4 matrices in column-major order) and "×" represents matrix

multiplication.

The window coordinates are then computed as follows:

winX = view(0) + view(2) (v’(0) + 1)/2

winY = view(1) + view(3) (v’(1) + 1)/2

winZ = (v(2) + 1)/ 2

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