Parametric Patch Rendering via Linear Segment Tessellation
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Solution Overview
Problem
Existing methods for rendering parametric patches in computer graphics, such as those used in PDF type 6 and 7 shadings, are inefficient and do not effectively utilize hardware acceleration, particularly in embedded systems with limited stack space, and struggle with non-linear color functions and multiple tessellation stages.
Innovation Solution
A method that approximates the shading color function using linear segments and determines tessellation points to tessellate the patch into cells, forming further cells by joining points of equal intermediate value and approximating isolines, allowing for efficient rendering using the intermediate values corresponding to vertices of the cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If recursive subdivision methods are used to tessellate parametric patches, then tessellation quality is improved, but device complexity and stack space requirements increase making it unsuitable for embedded systems
Solution Approach 1:
The patent divides the parametric patch into a structured grid of cells using non-recursive subdivision. Instead of recursively dividing the entire patch, it segments the patch into a regular grid pattern where each cell is independently processed, eliminating the need for deep stack space while maintaining tessellation quality.
Solution Approach 2:
The patent applies partial subdivision by only dividing the patch into a predetermined grid of cells rather than recursively subdividing until a quality threshold is met. This partial action is sufficient for embedded systems with limited resources while still providing acceptable tessellation quality.
2Manufacturing precision
If per-pixel rendering methods are used, then rendering quality is improved, but processing time and computational efficiency worsen
Solution Approach 1:
The patent segments the rendering process into cell-level operations rather than per-pixel operations. By computing intermediate values and colors at cell vertices and interpolating across cells, it reduces the number of computations from per-pixel to per-cell basis, significantly improving processing speed while maintaining quality.
Solution Approach 2:
The patent performs preliminary computation of intermediate values at cell vertices before rendering the actual pixel data. By pre-calculating these values and storing them in vertex buffers, it avoids redundant computations during the rendering phase, improving overall processing efficiency.
3Productivity
If predetermined tessellation depth is used, then processing speed is improved, but rendering quality deteriorates for shadings with non-linear color functions
Solution Approach 1:
The patent changes the approach from fixed-depth recursion to a grid-based cell subdivision where the number of cells can be adjusted. It introduces a parameter for the number of cells in each dimension, allowing flexible control of tessellation density to match the complexity of the shading function without requiring deep recursion.
4Manufacturing precision
If multiple tessellation stages are used, then tessellation quality is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent merges the geometric subdivision and color computation stages into a single unified process. Instead of separately tessellating the geometry and then computing colors, it computes intermediate values during the cell creation process itself, eliminating redundant processing stages and reducing overall system complexity.
Data Source
AI summary
A method of rendering a parametric patch. The patch is defined by a geometry and a color varying according to a surface mapping points of the patch to intermediate values. Each of the intermediate values is mapped to a color value according to a shading color function. A set of intermediate values is determined for the patch. The determined set of intermediate values represent an approximation of the shading color function by linear segments. The patch is tessellated into a plurality of cells. Tessellation points are determined for each of the plurality of cells according to the determined set of intermediate values. A further cell is formed for the patch by joining, within each of said plurality of cells, a plurality of the tessellation points being of equal intermediate value and approximating isolines of the surface. The patch is rendered using the intermediate values.