Sets a non-uniform rational B-spline (NURBS) property.
OpenGL C bindings library: libGL.a
void gluNurbsProperty(GLUnurbs* nurb, GLenum property, GLfloat value)
The gluNurbsProperty subroutine is used to control properties stored in a NURBS object. These properties affect the way that a NURBS curves is rendered. The following values are valid for the property parameter:
| 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. |
| GLU_SAMPLING_METHOD Value | Specifies how a NURBS surface should be tessellated.
The value parameter may be one of GLU_PATH_LENGTH,
GLU_PARAMETRIC_ERROR, or 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 Value | Specifies the maximum length, in pixels or in object space length unit, to use when the sampling methos 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 default value is 50.0 pixels. |
| GLU_PARAMETRIC_TOLERANCE Value | The Value parameter specifies the maximum distance, in pixels, to use when the sampling method is GLU_PARAMETRIC_ERROR. The initial value is 0.5. |
| GLU_U_STEP Value | The Value parameter 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 Value | The Value parameter specifies the number of sample points per unit length taken along the v axis in parametric coordinates. It is needed when GLU_SAMPLING_METHOD is set to GLU_DOMAIN_DISTANCE. The initial value is 100 |
| GLU_DISPLAY_MODE Value | The Value parameter defines how a NURBS surface should be rendered. The Value parameter can be set to the following: |
| Only one of these values can be used.
GLU_FILL causes the surface to be rendered as a set of polygons.
GLU_OUTLINE_POLYGON instructs the NURBS library to draw only the outlines of the
polygons created by tessellation. GLU_OUTLINE_PATCH causes just the outlines of
patches and trim curves defined by the user to be 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_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 default value is GLU_FILL. | |
| GLU_CULLING Value | The Value parameter 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 default is GL_FALSE. |
| GLU_AUTO_LOAD_MATRIX Value | The Value parameter is a Boolean value that, when set to GL_TRUE,
causes the NURBS code to download the projection matrix, the modelview matrix, and the
viewport from the OpenGL 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 of the viewport.
If this mode is set to GL_FALSE, the user must 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 subroutine. The default for this mode is GL_TRUE. Changing this mode 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.
Use the gluGetString subroutine to determine the GLU version.
| /usr/include/GL/gl.h | Contains C language constraints, variable type definitions, and ANSI function prototypes for OpenGL. |
The gluGetNurbsProperty subroutine, gluLoadSamplingMatrices subroutine, gluNewNurbsRenderer subroutine, gluGetString subroutine, gluNurbsCallback subroutine .