Name
EXT_object_space_tess
Name Strings
GLU_EXT_object_space_tess
Version
$Date: 1996/04/12
Number
75
Dependencies
None
Overview
This extension adds two object space tessellation methods for GLU nurbs
surfaces. The existing tessellation methods GLU_PATH_LENGTH and
GLU_PARAMETRIC_ERROR are view dependent since the error tolerance is
measured in the screen space (in pixels), while the corresponding object
space tessellation methods are view independent in that the error tolerance
measurement is in the object space.
New Procedures and Functions
None
New Tokens
Accepted by the parameter of NurbsProperty:
OBJECT_PARAMETRIC_ERROR_EXT 100208
OBJECT_PATH_LENGTH_EXT 100209
Errors
None
Additions to the GLU Specification Version 1.2, Section 7.6
NURBS properties
----------------
GLU_SAMPLING_METHOD specifies how a NURBS surface should be tessellated.
value may be set to 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 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 the users to specify, in parametric
coordinates, how many sample points per unit length are taken in u, v
dimension.
GLU_OBJECT_PATH_LENGTH_EXT is similar to GLU_PATH_LENGTH except that it is
view independent, that is, it specifies that 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, it specifies that
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 default value of GLU_SAMPLING_METHOD is GLU_PATH_LENGTH.
GLU_SAMPLING_TOLERANCE specifies the maximum distance, in pixels or
in object space when the sampling method is set to GLU_PATH_LENGTH or
GLU_OBJECT_PATH_LENGTH_EXT. The default value for GLU_SAMPLING_TOLERANCE
is 50.0.
GLU_PARAMETRIC_TOLERANCE specifies the maximum distance, in pixels or
in object space when the sampling method is set to GLU_PARAMETRIC_ERROR
or GLU_OBJECT_PARAMETRIC_ERROR_EXT. The default value for
GLU_PARAMETRIC_TOLERANCE is 0.5.