gluNurbsProperty() gluNurbsProperty()
gluNurbsProperty  set a NURBS property
void gluNurbsProperty(
GLUnurbs* nurb,
GLenum property,
GLfloat value );
Specifies the NURBS object (created with gluNewNurbsRenderer()).
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. 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: 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. 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. 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. 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. 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. 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. 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. 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. 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(3), gluLoadSamplingMatrices(3),
gluNewNurbsRenderer(3), gluGetString(3), gluNurbsCallback(3)
gluNurbsProperty()
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