GLUPROJECT

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NAME

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 )

delim $$

PARAMETERS

objX, 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 $v sup prime$ as follows:

v sup prime ~=~ P ~times~ M ~times~ v

where $P$ is the current projection matrix proj, $M$ is the current modelview matrix model (both represented as $4 times 4$ matrices in column-major order) and '$times$' represents matrix multiplication. The window coordinates are then computed as follows:

"winX" ~=~ "view" (0) ~+~ "view" (2) ~*~ (v sup prime (0) ~+~ 1)~/~2

"winY" ~=~ "view" (1) ~+~ "view" (3)~*~(v sup prime (1) ~+~ 1)~/~2 .EN

"winZ" ~=~ (v sup prime (2) ~+~ 1)~/~ 2