gluLoadSamplingMatrices

NAME

gluLoadSamplingMatrices -- load NURBS sampling and culling matrices

C SPECIFICATION

void gluLoadSamplingMatrices(GLUnurbsObj *nobj,
                             const GLfloat modelMatrix[16],
                             const GLfloat projMatrix[16],
                             const GLint viewport[4])

PARAMETERS

nobj
Specifies the NURBS object (created with gluNewNurbsRenderer).

modelMatrix
Specifies a modelview matrix (as from a glGetFloatv call).

projMatrix
Specifies a projection matrix (as from a glGetFloatv call).

viewport
Specifies a viewport (as from a glGetIntegerv call).

DESCRIPTION

gluLoadSamplingMatrices uses modelMatrix, projMatrix, and viewport to recompute the sampling and culling matrices stored in nobj. The sampling matrix determines how finely a NURBS curve or surface must be tessellated to satisfy the sampling tolerance (as determined by the GLU_SAMPLING_TOLERANCE property). The culling matrix is used in deciding if a NURBS curve or surface should be culled before rendering (when the GLU_CULLING property is turned on).

gluLoadSamplingMatrices is necessary only if the GLU_AUTO_LOAD_MATRIX property is turned off (see gluNurbsProperty). Although it can be convenient to leave the GLU_AUTO_LOAD_MATRIX property turned on, there can be a performance penalty for doing so. (A round trip to the OpenGL server is needed to fetch the current values of the modelview matrix, projection matrix, and viewport.)

SEE ALSO

gluGetNurbsProperty, gluNewNurbsRenderer, gluNurbsProperty

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© 1995 Uwe Behrens All rights reserved