Yamyam: 1版をインポートしました

2018-06-28T17:49:53Z

1版をインポートしました

wiki>Mindrones: moved Dev:Source/Blender/Render/BIHTree to Dev:Source/Render/BIHTree

2010-03-09T10:16:09Z

moved Dev:Source/Blender/Render/BIHTree to Dev:Source/Render/BIHTree

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=The Bounding Interval Hierarchy=
[[Image:Bih-incremental-subdivision-visualization.png|thumb|The incremental BIH tree after firing one ray diagonally through the standard Budhha model]]
The current method Blender employs for ray-scene intersection (i.e. efficiently intersecting every triangle in a scene with a ray) is the octree. While the octree is quite fast, it does not automatically adapt to scene geometry; it merely recursively divides the scene bounding box into eight children. The split locations at each recursion are always at the center of the bounding box.

However, there are many ray-scene acceleration structure options. In the graphics community, many papers and thesises have been written on the topic. [http://www.sci.utah.edu/~wald/PhD Wald's PhD thesis] showed that for the general case, the kdtree appears to have the most desirable characteristics.

So why a BIH tree for blender instead of a KDTree? The KDTree tends to have two problems: complicated implementation, and very slow building for a full surface-area-heuristic implementation. The SAH basically says that you pick the split location and dimension by checking all possible location/dimensions to see which one minimizes some cost function. This is what the BRL-CAD kdtree does, which is (badly) integrated into blender in [http://projects.blender.org/tracker/?func=detail&atid=127&aid=4345&group_id=9 this patch]. This ran dramatically slower than the octree for the scenes I tested with, because the build times were longer than the render times!

So, I decided to implement the new kid on the block: the BIH tree. [http://graphics.uni-ulm.de/BIH.pdf The paper] describing it was just released recently. I decided, upon reading about the ease of implementation yet results comparable to kdtrees with extremely fast build times, to implement BIH for blender.

=Plans in implementaion order=
* [done] Write BIH intersection code
** Though the code is clearly in need of bulletproofing
* Integrate BIH with blender
** Add new tab to render panel

=Links=
* [http://ompf.org/forum/ ompf raytracing forum]
* [http://ompf.org/forum/viewtopic.php?t=9 ompf essential raytracing links] - has several important papers and thesises

=BIH Implementaion Details=
* The tree is built incrementally; that is to say, only parts of the scene that have rays shot at them are indexed in detail.
* 64-bit clean
* Flat structure with (almost) no pointers; suitable for mmaping!
* Picture showing data structure coming soon.

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Dev:Source/Render/BIHTree - 版の履歴

Yamyam: 1版 をインポートしました

wiki>Mindrones: moved Dev:Source/Blender/Render/BIHTree to Dev:Source/Render/BIHTree

Yamyam: 1版をインポートしました