Cache Utilization Optimized Ray Traversal Algorithm with Minimized Memory Bandwidth Requirements

Abstract

Embodiments of the invention provide methods and apparatus for recording the traversal history of a ray through a spatial index structure and utilizing the recorded traversal history. An image processing system may initially determine which nodes a ray intersects as it traverses through a spatial index. Results of the node intersection determinations may be recorded as the ray traverses the spatial index, and the recorded determinations may be associated with the ray. Furthermore, the image processing system may decide upon a traversal path based upon some probability of striking primitives corresponding to the nodes which make up the spatial index. This traversal path may also be recorded and associated with the ray. If the image processing system needs to re-traverse the spatial index at a later time, the recorded traversal history may be used to eliminate the need to recalculate ray-node intersections, and eliminate incorrect traversal path determinations.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]Embodiments of the invention generally relate to the field of image processing.[0003]2. Description of the Related Art[0004]The process of rendering two-dimensional images from three-dimensional scenes is commonly referred to as image processing. As the modern computer industry evolves image processing evolves as well. One particular goal in the evolution of image processing is to make two-dimensional simulations or renditions of three-dimensional scenes as realistic as possible. One limitation of rendering realistic images is that modern monitors display images through the use of pixels.[0005]A pixel is the smallest area of space which can be illuminated on a monitor. Most modern computer monitors will use a combination of hundreds of thousands or millions of pixels to compose the entire display or rendered scene. The individual pixels are arranged in a grid pattern and collectively cover the entire viewing area of the...

AI Technical Summary

Benefits of technology

[0014]According to one embodiment of the invention a method of ray tracing utilizing a spatial index having nodes defining bounded volumes of a three dimensional scene is provided. The method generally comprising: generating a ray into the scene; traversing the spatial index by taking branches from internal nodes until a leaf node is reached, wherein branches are taken based on whether the ray intersects bounding volumes defined by the nodes; recording a traversal history indicating one or more nodes defining bounding volumes the ray intersects and branches taken when traversing the spatial index; determining if the ray hits a primitive contained in the bounding volume defined by the leaf node; and if the ray does not hit a primitive contained in the bounding volume defined by the leaf node, re-traversing the spatial index using the recorded traversal history.

[0015]According to another embodiment of the invention a computer readable medium containing a program which, when executed, performs an operation for ray tracing utilizing a spatial index having nodes defining bounded volumes of a three dimensional scene is provided. The operation generally comprising: generating a ray into the scene; traversing the spatial index by taking branches from internal nodes until a leaf node is reached, wherein branches are taken based on whether the ray intersects bounding volumes defined by the nodes; recording a traversal history indicating one or more nodes defining bounding volumes the ray intersects and branches taken when traversing the spatial index; determining if the ray hits a primitive contained in the bounding volume defined by the leaf node; and if the ray does not hit a primitive contained in the bounding volume defined by the leaf node, re-traversing the spatial index using the recorded traversal history.

[0016]According to another embodiment of the invention a system, is provided. The system generally comprising a spatial index having nodes defining bounded volumes of a three dimensional scene; and a first processing element, wherein the first processing element is generally configured to: generate a ray into the scene; traverse the spatial index by taking branches from internal nodes until a leaf node is reached, wherein branches are taken based on whether the ray intersects bounding volumes defined by the nodes; record a traversal history indicating one or more nodes defining bounding volumes the ray intersects and branches taken when traversing the spatial index; determine if the ray hits a primitive contained in the bounding volume defined by the leaf node; and if the ray does not hit a primitive contained in the bounding volume defined by the leaf node, re-traverse the spatial index using the recorded traversal history.

Problems solved by technology

One limitation of rendering realistic images is that modern monitors display images through the use of pixels.

Rasterization is effective at rendering graphics quickly and using relatively low amounts of computational power; however, rasterization suffers from some drawbacks.

For example, rasterization often suffers from a lack of realism because it is not based on the physical properties of light, rather rasterization is based on the shape of three-dimensional geometric objects in a scene projected onto a two dimensional plane.

Furthermore, the computational power required to render a scene with rasterization scales directly with an increase in the complexity of the scene to be rendered.

As image processing becomes more realistic, rendered scenes also become more complex.

Therefore, rasterization suffers as image processing evolves, because rasterization scales directly with complexity.

Furthermore, ray tracing also handles increases in scene complexity better than rasterization as scenes become more complex.

This is due to the fact that the same number of rays may be cast into a scene, even if the scene becomes more complex.

One major drawback of ray tracing is the large number of calculations, and thus processing power, required to render scenes.

This leads to problems when fast rendering is needed.

Due to the increased computational requirements for ray tracing it is difficult to render animation quickly enough to seem realistic (realistic animation is approximately twenty to twenty-four frames per second).

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