1Name
2
3    EXT_object_space_tess
4
5Name Strings
6
7    GLU_EXT_object_space_tess
8
9Version
10
11    $Date: 1996/04/12
12
13Number
14
15    75
16
17Dependencies
18
19    None
20
21Overview
22
23    This extension adds two object space tessellation methods for GLU nurbs 
24    surfaces. The existing tessellation methods GLU_PATH_LENGTH and 
25    GLU_PARAMETRIC_ERROR are view dependent since the error tolerance is 
26    measured in the screen space (in pixels), while the corresponding object
27    space tessellation methods are view independent in that the error tolerance
28    measurement is in the object space.
29  
30
31New Procedures and Functions
32
33   None
34
35New Tokens
36
37   Accepted by the <value> parameter of NurbsProperty:
38
39   OBJECT_PARAMETRIC_ERROR_EXT                       100208 
40   OBJECT_PATH_LENGTH_EXT                            100209
41
42Errors
43
44   None
45
46Additions to the GLU Specification Version 1.2, Section 7.6
47
48    NURBS properties
49    ----------------
50
51    GLU_SAMPLING_METHOD specifies how a NURBS surface should be tessellated. 
52    value may be set to one of GLU_PATH_LENGTH, GLU_PARAMETRIC_ERROR, 
53    GLU_DOMAIN_DISTANCE, GLU_OBJECT_PATH_LENGTH_EXT, or GLU_OBJECT_PARAMETRIC_ERROR_EXT. 
54    When set to 
55    GLU_PATH_LENGTH, the surface 
56    is rendered so that the maximum length, in pixels, of edges of the 
57    tessellation polygons is no greater than what is specified by 
58    GLU_SAMPLING_TOLERANCE. 
59    GLU_PARAMETRIC_ERROR specifies that
60    the surface is rendered in such a way that the value specified by
61    GLU_PARAMETRIC_TOLERANCE describes the maximum distance, in pixels,
62    between the tessellation polygons and the surfaces they approximate.
63    GLU_DOMAIN_DISTANCE allows the users to specify, in parametric  
64    coordinates, how many sample points per unit length are taken in u, v 
65    dimension. 
66    GLU_OBJECT_PATH_LENGTH_EXT  is similar to GLU_PATH_LENGTH except that it is
67    view independent, that is, it specifies that the surface is rendered so that
68    the maximum length, in object space, of edges of the tessellation polygons
69    is no greater than what is specified by GLU_SAMPLING_TOLERANCE.
70    GLU_OBJECT_PARAMETRIC_ERROR_EXT is similar to  GLU_PARAMETRIC_ERROR except
71    that it is view independent, that is, it specifies that 
72    the surface is rendered in such a way that the value specified by
73    GLU_PARAMETRIC_TOLERANCE describes the maximum distance, in object space,
74    between the tessellation polygons and the surfaces they approximate.
75    The default value of GLU_SAMPLING_METHOD is GLU_PATH_LENGTH.
76
77    GLU_SAMPLING_TOLERANCE specifies the maximum distance, in pixels or
78    in object space when the sampling method is set to GLU_PATH_LENGTH or
79    GLU_OBJECT_PATH_LENGTH_EXT. The default value for GLU_SAMPLING_TOLERANCE
80    is 50.0.
81
82    GLU_PARAMETRIC_TOLERANCE specifies the maximum distance, in pixels or
83    in object space when the sampling method is set to GLU_PARAMETRIC_ERROR
84    or GLU_OBJECT_PARAMETRIC_ERROR_EXT. The default value for 
85    GLU_PARAMETRIC_TOLERANCE is 0.5.
86
87
88   
89  
90