gluNurbsProperty man page on RedHat
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GLUNURBSPROPERTY(3G) OpenGL Manual GLUNURBSPROPERTY(3G)
NAME
gluNurbsProperty - set a NURBS property
C SPECIFICATION
void gluNurbsProperty(GLUnurbs* nurb, GLenum property, GLfloat value);
PARAMETERS
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.
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,
GLU_TRUE, GLU_FALSE, GLU_PATH_LENGTH, GLU_PARAMETRIC_ERROR,
GLU_DOMAIN_DISTANCE, GLU_NURBS_RENDERER, or GLU_NURBS_TESSELLATOR.
DESCRIPTION
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
value should be set to be either GLU_NURBS_RENDERER or
GLU_NURBS_TESSELLATOR. When set to GLU_NURBS_RENDERER, NURBS
objects are tessellated into OpenGL primitives and sent to the
pipeline for rendering. When set to GLU_NURBS_TESSELLATOR, 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. The
initial value is GLU_NURBS_RENDERER.
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, or GLU_OBJECT_PARAMETRIC_ERROR. 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 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 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. 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. 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 is set to be
GLU_NURBS_RENDERER, 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 is set to be GLU_NURBS_TESSELLATOR, value
defines how a NURBS surface should be tessellated. When
GLU_DISPLAY_MODE is set to GLU_FILL or GLU_OUTLINE_POLYGON, the
NURBS surface is tessellated into OpenGL triangle primitives that
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 that can be retrieved back through callback functions.
The initial value is GLU_FILL.
GLU_CULLING
value is a boolean value that, when set to GLU_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 GLU_FALSE.
GLU_AUTO_LOAD_MATRIX
value is a boolean value. When set to GLU_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 GLU_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 GLU_TRUE. Changing it from GLU_TRUE to
GLU_FALSE does not affect the sampling and culling matrices until
gluLoadSamplingMatrices() is called.
NOTES
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.
GLU_NURBS_MODE is only available if the GLU version is 1.3 or greater.
The GLU_OBJECT_PATH_LENGTH and GLU_OBJECT_PARAMETRIC_ERROR values for
the GLU_SAMPLING_METHOD property are only available if the GLU version
is 1.3 or greater.
SEE ALSO
gluGetNurbsProperty(), gluGetString(), gluLoadSamplingMatrices(),
gluNewNurbsRenderer(), gluNurbsCallback()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLUNURBSPROPERTY(3G)
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