Textures for Real-Time Ray Tracing Christian F. Ruff, Esteban W. G. - - PowerPoint PPT Presentation

Dynamic per Object Ray Caching Textures for Real-Time Ray Tracing

Christian F. Ruff, Esteban W. G. Clua and Leandro A. F. Fernandes Universidade Federal Fluminense (UFF)

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Ray Tracing

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Source: Wikipedia Source: NVidia

Ray Tracing

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Redundant rays image

Ray Tracing

• Can we store this information somewhere, and use it

later?

• Can we avoid the recursion of rays?
• It is possible to achieve coherent memory access?

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Related Work

• Ray tracing optimization:

– A. S. Glassner, “Space subdivision for fast ray tracing,” IEEE Comput.nGraph. Appl., vol. 4, no. 10, pp. 15–24, 1984. – T. Foley and J. Sugerman, “KD-tree acceleration structures for a GPU raytracer,” in Proc. of ACM SIGGRAPH/EUROGRAPHICS Conference on Graphics Hardware, 2005, pp. 15–22. – T. L. Sabino et al. “A hybrid GPU rasterized and ray traced rendering pipeline for real time rendering of per pixel effects,” in Entertainment Computing – ICEC, ser. LNCS. Springer, 2012, vol. 7522, pp. 292–305.

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Related Work

• Hybrid Ray Tracer:

– Compute the primary rays with deferred rendering in the rasterization step. – Use the OptiX engine only to compute the secondary rays from reflective and refractive objetcs. – Improved the frame rate up to 100% compared to standard OptiX implementation.

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Content

• Our Technique
• Results
• Limitations and Future Work
• Conclusion

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Our Technique

• Use 2D caching textures to store the color

information.

• Create a cube that contains the object, assign

a 2D texture to each face.

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Our Technique

• Use 2D caching textures to store the color

information.

• Create a cube that contains the object, assign

a 2D texture to each face.

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Our Technique

• Store the information of the ray tracing and

use it in subsequent frames.

• How to store this information?
• How to retrieve it?

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Our Technique

• Store the information:

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Our Technique

• Retrieve the information:

– The largest coordinate magnitude of the vector will determine the face

• f the cube.

– The formula: where m is the coordinate value related to the major axis direction of s in object space, and t’uand t’v are defined according to the OpenGL’s convention.

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Our Technique

• The textures begin to be filled and starts to retrieve the valid

information.

• After the textures are filled, the ray tracing will not be

executed anymore.

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After the first frame After a few frames

Results

• Image quality comparison:

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Ray tracing Our Technique

Results

• Image quality comparison:

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Ray tracing Our Technique

Results

• Image quality comparison:

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Ray tracing Our Technique

Results

• Image quality comparison:

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Results

• Performance comparison:

– Standard OptiX implementation

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Additional Reflective Objects Conventional Ray Tracing Speed Up Standard With Our Tehcnique 1 56.7 fps 57.8 fps ~ 2% 2 52.0 fps 55.6 fps ~ 7% 4 44.7 fps 51.8 fps ~15 % 8 32.8 fps 43.5 fps ~ 32% 16 17.1 fps 33.4 fps ~ 95% 32 8.0 fps 21.5fps ~ 168%

Results

• Performance comparison:

– Hybrid ray tracing

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Additional Reflective Objects Hybrid Ray Tracing Speed Up Standard With Our Tehcnique 68 fps 125 fps ~ 84% 1 63 fps 120 fps ~ 90% 2 59 fps 117 fps ~ 98% 4 49 fps 98 fps ~ 100% 8 38 fps 85 fps ~ 124% 16 23 fps 63 fps ~ 174% 32 12 fps 42 fps ~ 250%

Limitations and Future Work

• The tridimensionality of the relex information is lost,

since they are stored in 2D textures.

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Ray tracing Our Technique

Limitations and Future Work

• The tridimensionality of the relex information is lost,

since they are stored in 2D textures.

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Ray tracing Our Technique

• Use Relief Mapping to enhance the quality of the

reflex, restoring its tridimensionality.

Limitations and Future Work

• Dynamic scenes can generate invalid reflex

information.

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Limitations and Future Work

• Dynamic scenes can generate invalid reflex

information.

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• Use a visibility-graph-like structure to solve the

problems with dynamic objects in the scene.

Limitations and Future Work

• Concave objects may stored conflicting information
• n the textures.

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Limitations and Future Work

• Concave objects may stored conflicting information
• n the textures.

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Ray tracing Our Technique

Limitations and Future Work

• Concave objects may stored conflicting information
• n the textures.

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Ray tracing Our Technique

• Subdivide concave objects into convex parts to

eliminate the conflict when storing information.

Conclusion

• Overview:

– Create cubes around each object. – Store the color information in 2D caching textures. – Retrieve the information to use it in later frames.

• Contributions:

– No more recursive rays. – Coherent memory access. – Improved the performance.

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Conclusion

• Efficient cache strategy improved the frame rate of a

ray tracing implementation up to 250%.

• Replaces the computationally expensive bouncing of

rays by the texture sampling mechanism of the GPU.

• We believe that this idea will lead to further benefits

in the development of real-time ray tracing.

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Questions?

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