

 
GLUNURBSPROPERTY() 

GLUNURBSPROPERTY() 
gluNurbsProperty  set a NURBS property
void gluNurbsProperty( GLUnurbs* nurb,
GLenum property,
GLfloat value )
 nurb
 Specifies the NURBS object (created with gluNewNurbsRenderer).
 property
 Specifies the property to be set. Valid values are
GLU_SAMPLING_TOLERANCE, GLU_DISPLAY_MODE,
GLU_CULLING, GLU_AUTO_LOAD_MATRIX,
GLU_PARAMETRIC_TOLERANCE, GLU_SAMPLING_METHOD,
GLU_U_STEP, GLU_V_STEP, or GLU_NURBS_MODE_EXT.
 value
 Specifies the value of the indicated property. It may be a numeric value,
or one of GLU_OUTLINE_POLYGON, GLU_FILL,
GLU_OUTLINE_PATCH, GL_TRUE, GL_FALSE,
GLU_PATH_LENGTH, GLU_PARAMETRIC_ERROR,
GLU_DOMAIN_DISTANCE, GLU_NURBS_RENDERER_EXT, or
GLU_NURBS_TESSELLATOR_EXT.
gluNurbsProperty is used to control properties stored in a NURBS object.
These properties affect the way that a NURBS curve is rendered. The accepted
values for property are as follows:
 GLU_NURBS_MODE_EXT
 value should be set to be either GLU_NURBS_RENDERER_EXT or
GLU_NURBS_TESSELLATOR_EXT. When set to
GLU_NURBS_RENDERER_EXT, NURBS objects are tessellated into openGL
primitives and sent to the pipeline for rendering. When set to
GLU_NURBS_TESSELLATOR_EXT, NURBS objects are tessellated into
openGL primitives but the vertices, normals, colors, and/or textures are
retrieved back through a callback interface (see gluNurbsCallback).
This allows the user to cache the tessellated results for further
processing.
 GLU_SAMPLING_METHOD
 Specifies how a NURBS surface should be tessellated. value may be
one of GLU_PATH_LENGTH, GLU_PARAMETRIC_ERROR,
GLU_DOMAIN_DISTANCE, GLU_OBJECT_PATH_LENGTH_EXT, or
GLU_OBJECT_PARAMETRIC_ERROR_EXT. When set to
GLU_PATH_LENGTH, the surface is rendered so that the maximum
length, in pixels, of the edges of the tessellation polygons is no greater
than what is specified by GLU_SAMPLING_TOLERANCE.
 GLU_PARAMETRIC_ERROR specifies that the surface is rendered in such
a way that the value specified by GLU_PARAMETRIC_TOLERANCE
describes the maximum distance, in pixels, between the tessellation
polygons and the surfaces they approximate.
 GLU_DOMAIN_DISTANCE allows users to specify, in parametric
coordinates, how many sample points per unit length are taken in u,
v direction.
 GLU_OBJECT_PATH_LENGTH_EXT is similar to GLU_PATH_LENGTH
except that it is view independent, that is, the surface is rendered so
that the maximum length, in object space, of edges of the tessellation
polygons is no greater than what is specified by
GLU_SAMPLING_TOLERANCE.
 GLU_OBJECT_PARAMETRIC_ERROR_EXT is similar to
GLU_PARAMETRIC_ERROR except that it is view independent, that is,
the surface is rendered in such a way that the value specified by
GLU_PARAMETRIC_TOLERANCE describes the maximum distance, in object
space, between the tessellation polygons and the surfaces they
approximate.
 The initial value of GLU_SAMPLING_METHOD is
GLU_PATH_LENGTH.
 GLU_SAMPLING_TOLERANCE
 Specifies the maximum length, in pixels or in object space length unit, to
use when the sampling method is set to GLU_PATH_LENGTH or
GLU_OBJECT_PATH_LENGTH_EXT. The NURBS code is conservative when
rendering a curve or surface, so the actual length can be somewhat
shorter. The initial value is 50.0 pixels.
 GLU_PARAMETRIC_TOLERANCE
 Specifies the maximum distance, in pixels or in object space length unit,
to use when the sampling method is GLU_PARAMETRIC_ERROR or
GLU_OBJECT_PARAMETRIC_ERROR_EXT. The initial value is 0.5.
 GLU_U_STEP
 Specifies the number of sample points per unit length taken along the
u axis in parametric coordinates. It is needed when
GLU_SAMPLING_METHOD is set to GLU_DOMAIN_DISTANCE. The
initial value is 100.
 GLU_V_STEP
 Specifies the number of sample points per unit length taken along the
v axis in parametric coordinate. It is needed when
GLU_SAMPLING_METHOD is set to GLU_DOMAIN_DISTANCE. The
initial value is 100.
 GLU_DISPLAY_MODE
 value can be set to GLU_OUTLINE_POLYGON, GLU_FILL, or
GLU_OUTLINE_PATCH. When GLU_NURBS_MODE_EXT is set to be
GLU_NURBS_RENDERER_EXT, value defines how a NURBS surface
should be rendered. When value is set to GLU_FILL, the
surface is rendered as a set of polygons. When value is set to
GLU_OUTLINE_POLYGON, the NURBS library draws only the outlines of
the polygons created by tessellation. When value is set to
GLU_OUTLINE_PATCH just the outlines of patches and trim curves
defined by the user are drawn.
 When GLU_NURBS_MODE_EXT is set to be
GLU_NURBS_TESSELLATOR_EXT, value defines how a NURBS surface
should be tessellated. When GLU_DISPLAY_MODE is set to
GLU_FILL or GLU_OUTLINE_POLY, the NURBS surface is
tessellated into openGL triangle primitives which can be retrieved back
through callback functions. If GLU_DISPLAY_MODE is set to
GLU_OUTLINE_PATCH, only the outlines of the patches and trim curves
are generated as a sequence of line strips which can be retrieved back
through callback functions.
 The initial value is GLU_FILL.
 GLU_CULLING
 value is a boolean value that, when set to GL_TRUE,
indicates that a NURBS curve should be discarded prior to tessellation if
its control points lie outside the current viewport. The initial value is
GL_FALSE.
 GLU_AUTO_LOAD_MATRIX
 value is a boolean value. When set to GL_TRUE, the NURBS
code downloads the projection matrix, the modelview matrix, and the
viewport from the GL server to compute sampling and culling matrices for
each NURBS curve that is rendered. Sampling and culling matrices are
required to determine the tessellation of a NURBS surface into line
segments or polygons and to cull a NURBS surface if it lies outside the
viewport.
 If this mode is set to GL_FALSE, then the program needs to provide
a projection matrix, a modelview matrix, and a viewport for the NURBS
renderer to use to construct sampling and culling matrices. This can be
done with the gluLoadSamplingMatrices function. This mode is
initially set to GL_TRUE. Changing it from GL_TRUE to
GL_FALSE does not affect the sampling and culling matrices until
gluLoadSamplingMatrices is called.
If GLU_AUTO_LOAD_MATRIX is true, sampling and culling may be executed
incorrectly if NURBS routines are compiled into a display list.
A property of GLU_PARAMETRIC_TOLERANCE,
GLU_SAMPLING_METHOD, GLU_U_STEP, or GLU_V_STEP, or a
value of GLU_PATH_LENGTH, GLU_PARAMETRIC_ERROR,
GLU_DOMAIN_DISTANCE are only available if the GLU version is 1.1 or
greater. They are not valid parameters in GLU 1.0.
gluGetString can be used to determine the GLU version.
gluGetNurbsProperty, gluLoadSamplingMatrices,
gluNewNurbsRenderer, gluGetString, gluNurbsCallback
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