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<STRONG>NAME</STRONG>
<STRONG>gluNurbsProperty</STRONG> - set a NURBS property
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>gluNurbsProperty</STRONG>( GLUnurbs* <EM>nurb</EM>,
GLenum <EM>property</EM>,
GLfloat <EM>value</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>nurb</EM> Specifies the NURBS object (created with
<STRONG>gluNewNurbsRenderer</STRONG>).
<EM>property</EM> Specifies the property to be set. Valid values are
<STRONG>GLU_SAMPLING_TOLERANCE</STRONG>, <STRONG>GLU_DISPLAY_MODE</STRONG>,
<STRONG>GLU_CULLING</STRONG>, <STRONG>GLU_AUTO_LOAD_MATRIX</STRONG>,
<STRONG>GLU_PARAMETRIC_TOLERANCE</STRONG>, <STRONG>GLU_SAMPLING_METHOD</STRONG>,
<STRONG>GLU_U_STEP</STRONG>, <STRONG>GLU_V_STEP</STRONG>, or <STRONG>GLU_NURBS_MODE_EXT</STRONG>.
<EM>value</EM> Specifies the value of the indicated property. It
may be a numeric value, or one of
<STRONG>GLU_OUTLINE_POLYGON</STRONG>, <STRONG>GLU_FILL</STRONG>, <STRONG>GLU_OUTLINE_PATCH</STRONG>,
<STRONG>GL_TRUE</STRONG>, <STRONG>GL_FALSE</STRONG>, <STRONG>GLU_PATH_LENGTH</STRONG>,
<STRONG>GLU_PARAMETRIC_ERROR</STRONG>, <STRONG>GLU_DOMAIN_DISTANCE</STRONG>,
<STRONG>GLU_NURBS_RENDERER_EXT</STRONG>, or
<STRONG>GLU_NURBS_TESSELLATOR_EXT</STRONG>.
<STRONG>DESCRIPTION</STRONG>
<STRONG>gluNurbsProperty</STRONG> 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 <EM>property</EM> are as
follows:
<STRONG>GLU_NURBS_MODE_EXT</STRONG>
<EM>value</EM> should be set to be either
<STRONG>GLU_NURBS_RENDERER_EXT</STRONG> or
<STRONG>GLU_NURBS_TESSELLATOR_EXT</STRONG>. When set to
<STRONG>GLU_NURBS_RENDERER_EXT</STRONG>, NURBS objects are
tessellated into openGL primitives and sent
to the pipeline for rendering. When set to
<STRONG>GLU_NURBS_TESSELLATOR_EXT</STRONG>, NURBS objects are
tessellated into openGL primitives but the
vertices, normals, colors, and/or textures
are retrieved back through a callback
interface (see <STRONG>gluNurbsCallback</STRONG>). This allows
the user to cache the tessellated results for
further processing.
<STRONG>GLU_SAMPLING_METHOD</STRONG>
Specifies how a NURBS surface should be
tessellated. <EM>value</EM> may be one of
<STRONG>GLU_PATH_LENGTH</STRONG>, <STRONG>GLU_PARAMETRIC_ERROR</STRONG>,
<STRONG>GLU_DOMAIN_DISTANCE</STRONG>,
<STRONG>GLU_OBJECT_PATH_LENGTH_EXT</STRONG>, or
<STRONG>GLU_OBJECT_PARAMETRIC_ERROR_EXT</STRONG>. When set to
<STRONG>GLU_PATH_LENGTH</STRONG>, 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
<STRONG>GLU_SAMPLING_TOLERANCE</STRONG>.
<STRONG>GLU_PARAMETRIC_ERROR</STRONG> specifies that the
surface is rendered in such a way that the
value specified by <STRONG>GLU_PARAMETRIC_TOLERANCE</STRONG>
describes the maximum distance, in pixels,
between the tessellation polygons and the
surfaces they approximate.
<STRONG>GLU_DOMAIN_DISTANCE</STRONG> allows users to specify,
in parametric coordinates, how many sample
points per unit length are taken in <EM>u</EM>, <EM>v</EM>
direction.
<STRONG>GLU_OBJECT_PATH_LENGTH_EXT</STRONG> is similar to
<STRONG>GLU_PATH_LENGTH</STRONG> 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
<STRONG>GLU_SAMPLING_TOLERANCE</STRONG>.
<STRONG>GLU_OBJECT_PARAMETRIC_ERROR_EXT</STRONG> is similar to
<STRONG>GLU_PARAMETRIC_ERROR</STRONG> except that it is view
independent, that is, the surface is rendered
in such a way that the value specified by
<STRONG>GLU_PARAMETRIC_TOLERANCE</STRONG> describes the
maximum distance, in object space, between
the tessellation polygons and the surfaces
they approximate.
The initial value of <STRONG>GLU_SAMPLING_METHOD</STRONG> is
<STRONG>GLU_PATH_LENGTH</STRONG>.
<STRONG>GLU_SAMPLING_TOLERANCE</STRONG>
Specifies the maximum length, in pixels or in
object space length unit, to use when the
sampling method is set to <STRONG>GLU_PATH_LENGTH</STRONG> or
<STRONG>GLU_OBJECT_PATH_LENGTH_EXT</STRONG>. 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.
<STRONG>GLU_PARAMETRIC_TOLERANCE</STRONG>
Specifies the maximum distance, in pixels or
in object space length unit, to use when the
sampling method is <STRONG>GLU_PARAMETRIC_ERROR</STRONG> or
<STRONG>GLU_OBJECT_PARAMETRIC_ERROR_EXT</STRONG>. The initial
value is 0.5.
<STRONG>GLU_U_STEP</STRONG> Specifies the number of sample points per
unit length taken along the <EM>u</EM> axis in
parametric coordinates. It is needed when
<STRONG>GLU_SAMPLING_METHOD</STRONG> is set to
<STRONG>GLU_DOMAIN_DISTANCE</STRONG>. The initial value is
100.
<STRONG>GLU_V_STEP</STRONG> Specifies the number of sample points per
unit length taken along the <EM>v</EM> axis in
parametric coordinate. It is needed when
<STRONG>GLU_SAMPLING_METHOD</STRONG> is set to
<STRONG>GLU_DOMAIN_DISTANCE</STRONG>. The initial value is
100.
<STRONG>GLU_DISPLAY_MODE</STRONG>
<EM>value</EM> can be set to <STRONG>GLU_OUTLINE_POLYGON</STRONG>,
<STRONG>GLU_FILL</STRONG>, or <STRONG>GLU_OUTLINE_PATCH</STRONG>. When
<STRONG>GLU_NURBS_MODE_EXT</STRONG> is set to be
<STRONG>GLU_NURBS_RENDERER_EXT</STRONG>, <EM>value</EM> defines how a
NURBS surface should be rendered. When <EM>value</EM>
is set to <STRONG>GLU_FILL</STRONG>, the surface is rendered
as a set of polygons. When <EM>value</EM> is set to
<STRONG>GLU_OUTLINE_POLYGON</STRONG>, the NURBS library draws
only the outlines of the polygons created by
tessellation. When <EM>value</EM> is set to
<STRONG>GLU_OUTLINE_PATCH</STRONG> just the outlines of
patches and trim curves defined by the user
are drawn.
When <STRONG>GLU_NURBS_MODE_EXT</STRONG> is set to be
<STRONG>GLU_NURBS_TESSELLATOR_EXT</STRONG>, <EM>value</EM> defines how
a NURBS surface should be tessellated. When
<STRONG>GLU_DISPLAY_MODE</STRONG> is set to <STRONG>GLU_FILL</STRONG> or
<STRONG>GLU_OUTLINE_POLY</STRONG>, the NURBS surface is
tessellated into openGL triangle primitives
which can be retrieved back through callback
functions. If <STRONG>GLU_DISPLAY_MODE</STRONG> is set to
<STRONG>GLU_OUTLINE_PATCH</STRONG>, 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 <STRONG>GLU_FILL</STRONG>.
<STRONG>GLU_CULLING</STRONG> <EM>value</EM> is a boolean value that, when set to
<STRONG>GL_TRUE</STRONG>, indicates that a NURBS curve should
be discarded prior to tessellation if its
control points lie outside the current
viewport. The initial value is <STRONG>GL_FALSE</STRONG>.
<STRONG>GLU_AUTO_LOAD_MATRIX</STRONG>
<EM>value</EM> is a boolean value. When set to
<STRONG>GL_TRUE</STRONG>, 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 <STRONG>GL_FALSE</STRONG>, 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 <STRONG>gluLoadSamplingMatrices</STRONG> function. This
mode is initially set to <STRONG>GL_TRUE</STRONG>. Changing
it from <STRONG>GL_TRUE</STRONG> to <STRONG>GL_FALSE</STRONG> does not affect
the sampling and culling matrices until
<STRONG>gluLoadSamplingMatrices</STRONG> is called.
<STRONG>NOTES</STRONG>
If <STRONG>GLU_AUTO_LOAD_MATRIX</STRONG> is true, sampling and culling may be
executed incorrectly if NURBS routines are compiled into a
display list.
A <EM>property</EM> of <STRONG>GLU_PARAMETRIC_TOLERANCE</STRONG>, <STRONG>GLU_SAMPLING_METHOD</STRONG>,
<STRONG>GLU_U_STEP</STRONG>, or <STRONG>GLU_V_STEP</STRONG>, or a <EM>value</EM> of <STRONG>GLU_PATH_LENGTH</STRONG>,
<STRONG>GLU_PARAMETRIC_ERROR</STRONG>, <STRONG>GLU_DOMAIN_DISTANCE</STRONG> are only available
if the GLU version is 1.1 or greater. They are not valid
parameters in GLU 1.0.
<STRONG>gluGetString</STRONG> can be used to determine the GLU version.
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>gluGetNurbsProperty</STRONG>, <STRONG>gluLoadSamplingMatrices</STRONG>,
<STRONG>gluNewNurbsRenderer</STRONG>, <STRONG>gluGetString</STRONG>, <STRONG>gluNurbsCallback</STRONG>
</PRE>
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