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