Indirection Maps for Texture Space Sub-Surface Scattering
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Solution Overview
Problem
Realistically modeling sub-surface scattering effects in three-dimensional objects for computer-generated graphics is challenging due to the difficulty in creating a contiguous two-dimensional representation without artificial seams, leading to undesirable artifacts in rendered images.
Innovation Solution
An indirection map is generated to redirect sampling regions across seams in the two-dimensional representation to their correct spatial locations in the texture map, ensuring accurate application of sub-surface scattering effects without loss of data or artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the three-dimensional mesh is unwrapped into a two-dimensional representation, then the sub-surface scattering effect can be approximated by blurring the texture map, but artificial seams appear in the rendered image causing undesirable artifacts
Solution Approach 1:
The patent segments the two-dimensional texture map into multiple overlapping patches. Each patch is processed independently for sub-surface scattering effects, and then the patches are blended together using smooth transitions. This segmentation approach allows the scattering effect to be applied locally without creating visible seams at the boundaries of the entire texture map.
Solution Approach 2:
The patent applies different processing qualities to different regions of the texture map. Specifically, regions that would normally contain seams are given special treatment through overlapping patches and smooth blending, while other regions use standard blurring. This local quality adjustment ensures that problematic areas receive enhanced processing to eliminate artifacts while maintaining efficiency in other areas.
2Object-affected harmful factors
If smaller sampling windows are used to reduce the visibility of seams, then the defects become less obvious, but the blurring effect becomes less realistic
Solution Approach 1:
The patent transitions from processing the entire texture map in one dimension to processing multiple overlapping two-dimensional patches simultaneously. This dimensional approach allows larger sampling windows to be used within each patch for realistic blurring, while the overlapping and blending mechanism in the second dimension ensures that seams are eliminated. The problem is solved by moving from a single large processing window to multiple smaller overlapping windows in a different spatial arrangement.
3Object-affected harmful factors
If additional layers or accessories are superimposed to hide seams, then the seams are concealed, but additional time and labor are required
Solution Approach 1:
The patent performs preliminary action by pre-processing the texture map into overlapping patches and establishing the blending strategy before applying the sub-surface scattering effects. This preliminary organization of the texture space allows the main rendering process to proceed efficiently without requiring additional post-processing layers or accessories to hide seams. The seam elimination is built into the fundamental processing approach rather than being added as a separate corrective step.
Data Source
AI summary
Embodiments of the present invention are directed to a novel approach for realistically modeling sub-surface scattering effects in three-dimensional objects of graphically rendered images. In an embodiment, an indirection map is generated for an image by analyzing the triangle mesh of one or more three-dimensional objects in the image and identifying pairs of edges between adjacent triangles in the mesh that have the same spatial locations in the three-dimensional representations, but which have different locations in the texture map. For each of these edges, the opposite triangle in each pair is projected into their corresponding edge's two-dimensional space. This allows samples which cross a seam in the two dimensional representation that would otherwise sample out into invalid data to be redirected to the spatially correct region of the texture and generate consistent results with non-seam areas.