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 <value> 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.