Patent ID: 7362328

Claim:
An interface for use in a 3-d graphics system comprising a parametric modelling unit for modelling objects as high order surfaces and a polygon based rendering system for rendering polygon modelled objects for display, the interface comprising: a) an input, for receiving data representing at least one high order surface patch; b) a subdivision unit, coupled to the input, for processing the data to form leaf patch data representing the patch at a first level of subdivision and for further processing the data to form sub-leaf patch data representing the patch at a second level of subdivision; c) a converter, coupled to the subdivision unit, for determining from the leaf patch data a first plurality of values representing vertices of tessellating polygons describing the leaf patch, and for determining from the sub-leaf patch data a second plurality of values representing the vertices of tessellating polygons describing the sub-leaf patch; d) a combiner, coupled to the converter, for combining the first and second plurality of values to form leaf polygon data defining the polygon vertices at the first subdivision level, wherein the combiner is a weighting processor for performing a weighted average of the first and second plurality of values; and e) an output, coupled to the combiner, for outputting the leaf polygon data.