skia / external / github.com / KhronosGroup / OpenGL-Registry / bf41341037b0fc7f1c7c6c0358b9c27afdac254a / . / extensions / EXT / GLU_EXT_object_space_tess.txt

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. | |