[Bf-committers] BIH progress update

[Joe Eagar]

Code specific to only 1 architecture isn't allowed.  However, I think if 
you wrote a generic SIMD macro library and used *it* then it'd be ok.  
At least that was what I was planning on doing back when I was 
considering using SSE for something (using SSE by itself had already 
been vetoed at that point, but I figured a generic macro library could 
support Altivec too, so it wouldn't really be architecture-specific 
anymore).

BTW, do you have a link to that forum post? It sounds cool.

Joe

Yves Poissant wrote:
> This is a head-up to give a status report about the BIH implementation I'm 
> working on.
>
> I just spent the last 5 days working on BIH. Not much progress 
> unfortunately. On some file, I get spectacular improvement, up to 4 times 
> faster render times than octree. But on some other files, I can get 
> humongous render times. On average, there is very little gain. I tried all 
> the optimizing tricks I know, including caching the quad data, but that 
> gained very little too. I rewrote the tree building algorithm to allow me to 
> test different partitioning heuristics but I have not started on that yet. 
> I've added code to cut out empty space but that deepens the tree and 
> lengthens the total render time. As I added code to cut off empty space, the 
> partitioning process looked more and more like a defered BVH so I'm begining 
> to think that I should try a SAH BVH just to get a comparison point. I 
> haven't touched on the ray-triangle intersection aspect yet because the 
> partitioning complexity is way too high right now and that needs to be 
> optimized first. I need get data out of the partitioning and traversal for 
> the scenes that takes huge render times to figure what makes those scenes 
> behave that bad.
>
> I thought of giving this head-up because I will now have to return to my 
> regular work for a while but I will be back on the BIH later. I'm sure the 
> back burner will keep the issue warm in my head though.
>
> What is the policy about using SSE ? Someone posted an SSE function on ompf 
> forum that computes intersections between one ray and 4 triangles in 
> parallel and at some point I'd like to try that. Since quads are 2 triangles 
> and I currently store 2 quads per leaves, that would fit very well. SSE 
> could also be used efficiently when doing bounding boxes operations.
>
> Yves 
>
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