Secondary Ray Origin Offsets for Realistic 3D Shadowing
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Solution Overview
Problem
Ray tracing for rendering realistic images is computationally expensive due to the need for intersection testing between rays and large numbers of geometric primitives, leading to increased memory requirements and unrealistic shadowing effects when casting secondary rays from planar polygon surfaces.
Innovation Solution
Introduce secondary rays with origins offset from the surface, determined by vectors associated with the intersected surface vertices, using implicit higher-order surfaces to vary the offset amount based on the intersection location, and apply these offsets to improve shadowing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary rays are cast from planar polygon surfaces, then shadowing effects can be determined, but hard and unrealistic shadowing effects occur
Solution Approach 1:
The patent applies parameter changes by offsetting the origin of secondary rays from the surface along the normal direction by a variable distance. This offset parameter is determined by the local surface curvature and the distance to light sources, transforming the ray origin position parameter to achieve soft, realistic shadowing effects while maintaining computational feasibility with low-polygon models.
2Manufacturing precision
If polygon count is increased to reduce deviation from original surface, then surface accuracy improves, but memory requirements increase
Solution Approach 1:
The patent introduces an intermediary computational approach by using offset secondary rays that account for surface curvature effects without requiring increased geometric detail. The offset distance acts as a mediator that compensates for the simplicity of low-polygon models, allowing accurate shadowing and lighting calculations while maintaining low memory requirements.
3Manufacturing precision
If ray tracing is implemented with detailed surface modeling, then rendering accuracy improves, but computational cost increases
Solution Approach 1:
The patent applies local quality by varying the offset parameter of secondary ray origins based on local surface properties such as curvature and distance to light sources. Rather than uniformly increasing model complexity everywhere, the offset approach applies localized corrections only where and how they are needed for accurate shadowing and lighting, reducing overall computational cost while maintaining rendering accuracy.
Data Source
AI summary
During tracing of a primary ray in a 3-D space (e.g., a 3-D scene in graphics rendering), a ray is found to intersect a primitive (e.g., a triangle) located in the 3-D space. Secondary ray(s) may be generated for a variety of purposes. For example, occlusion rays may be generated to test occlusion of a point of intersection between the primary ray and primitive is illuminated by any of the light(s). An origin for each secondary ray can be modified from the intersection point based on characteristics of the primitive intersected. For example, an offset from the intersection point can be calculated using barycentric coordinates of the intersection point and interpolation of one or more parameters associated with vertices defining the primitive. These parameters may include a size of the primitive and differences between a geometric normal for the primitive and a respective additional vector supplied with each vertex.