Using the SPU's to do visibility culling

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purpledog

Newcomer
Well apparently using SPU to compute some visibility term has already been done so feel free to post any relevant link.

http://forum.beyond3d.com/showpost.php?p=1061199&postcount=12
http://forum.beyond3d.com/showthread.php?p=1028174&highlight=occlusion#post1028174
http://forum.beyond3d.com/showpost.php?p=1061561&postcount=65

Questions:
- is it per-triangle? per-"object"?
- any use of (hierarchical?) bounding boxes?
- is it based on something similar as the GL_ARB_OCCLUSION_QUERY? Does the SPU rasterize? screen-res?
- maybe cell-based visibility?
- does it use time-coherency?
 
C'monnnnnnn...

This is about one the 2 fundamental pillows to achieve consistent frame rate, this is happening on one of those nice little <deleted> named SPU, and nobody want to take a chance???? :smile:

Maybe somebody has an idea about how costly it is to rasterixe on an SPU (depth only)? Same throughput as GPU?
 
Last edited by a moderator:
I havent read papers or anything but it's most-likely per-object.

Per-triangle would be insanely expensive, even on high-end PCs
 
we already know a few ps3 titles are doing per triangle frustum culling / back facing tri culling with cell
cloudscapes - as wowfactor saiz, cell thrashes even the fastest intel/amd cpus at this, so why for pc its not worth it, for the ps3 it is

perhaps its cpu occlusion based, http://www.umbra.fi/ i notice sony are one of the clients
 
The whole point of it is that it is at the triangle level, object-level culling is normal to do on CPUs.

For example, this guy - one of the biggest names in the Russian gamedev scene - achieves 200 mln triangles per second transformed and backface culled on one SPU (half of them pass, half fail the culling test) - this corresponds to 3.33 mln triangles per frame at 60 fps, which is a very sensible number, actually twice above what we hear on this forum is normal geometry load for next-gen console titles.

It has nothing to do with the umbra/dPVS guys. Sony are a client AFAIK with their PC-based MMOs.
 
nAo said:
No, meaning that Edge performs more than just back face culling
Click to expand...


That's what I was pointing towards during my last statement; that Edge (SPUs) are doing more than just back face culling.


Meaning the SPUs aren't doing nothing else (i.e. no sound, physics, etc...) but back face culling...right?
Click to expand...

When I said this^^...was about/on assen link.
 
No :) sorry..my bad, I didn't explain it clearly. What I meant is that Edge performs other operations devoted to cull not back facing but still not visible triangles.
Edge culling code is more complex than the aforementioned back facing culling code, so it's likely to be slower as well.
EDIT: whatever! I think we understood each other!
 
nAo said:
No :) sorry..my bad, I didn't explain it clearly. What I meant is that Edge performs other operations devoted to cull not back facing but still not visible triangles.
Edge culling code is more complex than the aforementioned back facing culling code, so it's likely to be slower as well.
Click to expand...


OOOOOOOOOOOOOOOOooooooooooooo!! :LOL:
 
Yes, this speed is when ONLY ONE SPU is doing ONLY backface culling.

The Russian mafia is everywhere ;-)
 
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