Cell Can't Texture Map Well?

**udontneed2know** · 03-26-2006

Barry Minor of IBM has a different opinion and he and some buddies worked on a raytracing algorithm with texture maps running completely off Cell(PS3 version, 7 SPE's w/ 256MB XDR ). The results are flabbergasting to say the least. This is a CPU doing this people, not a GPU.

http://gametomorrow.com/blog/index.p...-cant-texture/

ch has been said about Cell’s presumed inability to texture map well. Given the small (256KB) local stores and DMA memory access, the SPEs were relegated by many to only handle nice streaming geometry type workloads. This seemed like an issue ripe for a little prototyping.

First, colleague Mark Nutter, implemented a software cache abstraction layer for the SPE giving us the ability to both hide the complexity of DMAs and benefit from transparent data reuse. Next, given the lessons learned from this paper, we tiled our textures, optimized our access patterns, and implemented several cache replacement policies. We then rewrote the shader in the Quaternion Julia Set Raytracer to add five cubemap texture lookup passes - 3 refraction lookups, a reflection lookup, plus a background lookup. These five texture lookups were then blended together with a fresnel calculation and modulated with the base lighting computation to form the final sample color.

We found that even with small 4-way set associative software cache sizes (8 KB), miss rates for this renderer were a low 7% and hit access times were only 12 SPE cycles.

Using only seven 3.2 GHz SPEs we were able to raytrace 15 frames per second with a frame resolution of 1024×1024. The texture buffer held a cubemap with 1024×1024x16 bit texel faces resulting in a 12.5 MB texture buffer in XDR system memory. The performance penalty for using the five pass texture shader vs the lighting only shader was just 13%.

Our miss handler was implemented as a blocking function and we still have ideas pending to further reduce the 12 cycle software cache hit access time so we believe the 13% performance gap between the two shaders will continue to close.

Trully amazing.

Edit: As numerous people have posted on this thread already, there is a video at the URL link as well. Quicktime download, 16MB. Recommend alert 1, download the video.

**Trinity** · 03-26-2006

Thats right truly amazing. The first pic is just fantastic, jaw dropping. Thanks for sharing dude.

**C64isStillTheBest** · 03-26-2006

I always enjoy the articles about the power of Cell. It's a truly remarkable chip and I do hope it also catches on in PCs eventually.

**surtur** · 03-26-2006

http://www.gametomorrow.com/minor/barry/julia.mov
that is the video for it from that site i didn't see you link the video. IMPRESIVE..

**Fredag** · 03-26-2006

Dont forget to check the video:
http://www.gametomorrow.com/minor/barry/julia.mov

**udontneed2know** · 03-26-2006

Trully amazing for a CPU to be capable of such a thing. That looks like something you'd see in a GPU benchmark, not a CPU raytracing demonstration running at a smooth 15FPS at an insane resolution utilizing only 8kb chunks of data and only 12.5MB of XDR in the end.

One of the more impressive things I've ever seen. Besides all the duck demos and The Getaway at E3, which was running off nothing but Cell. Gotta love the way it smoothly morphs. Almost looks like a fluid floating in the air being molded by God's hands or something lol.

Tribunal · 03-26-2006

udontneed2know you always know how to say the right things.

**MGSfanForLYFE** · 03-26-2006

so are we gonna see things like that on our games? or is just a show off

**Itaintrite** · 03-26-2006

It's just a tech demo demonstrating what the Cell is capable of ALONE. I doubt we'll be seeing this level of graphics ingame anytime soon, at least, not this clear anyway.

**udontneed2know** · 03-26-2006

Just a show off demonstration. People have been saying Cell wouldn't be capable of any good texture mapping considering the SPE's only have 256KB of local storage to work with and because of the excessive DMA accesses. So IBM went out and proved em wrong with this demonstration which uses only 8kb data chunks and overall only 12.5MB of the XDR Ram avaliable.

It just helps solidify mine and many other peoples thoughts that Cell will indeed be an incredible companion GPU to the RSX GPU. Its a real nice luxury for developers to be able to count on the CPU to do things like stream geometry ( I'm sure Rockstar will use this for PS3 GTA ) and help out on texture maps and all other types of stuff. This is why I called the Cell the first real hybrid GCPU. A CPU thats more then capable of producing its own impressive graphics and effects and do it in alot of cases better then a GPU could. I think this demonstration here when done on a GPU is 5-6x slower.

Tribunal · 03-26-2006

Originally Posted by Itaintrite

It's just a tech demo demonstrating what the Cell is capable of ALONE. I doubt we'll be seeing this level of graphics ingame anytime soon, at least, not this clear anyway.

Cell+RSX, doubt is a powerful thing, but so are those.

**Panda Bear Shenyu** · 03-26-2006

Wow, I was pretty sure that first pic was a photo (the last two are awesome but too small to judge)
I am pretty sure tha is photoshop realism right them, and only on the CELL! (I read in one article that the Cell is actually capable of doing more of that texture mapping stuff than the RSX but Ken dubbed doing THAT as a "waste of the Cell's immense resources")

**ShinMaruku** · 03-26-2006

If we have a good enough group of devs working deilignetly we should expect to see great things from the cell and RSX...

**Alkemist** · 03-26-2006

Originally Posted by surtur

IMPRESIVE..

Most Impressive. Good find udn2k.

**wrathofall** · 03-26-2006

There is a video of this also (16 MB Quick Time - BE PATIENT):

http://www.gametomorrow.com/minor/barry/julia.mov

**Deldwen** · 03-26-2006

Crazy, thats really cool. Cant wait for ps3 nice find

**sevendesigns** · 03-26-2006

Originally Posted by wrathofall

There is a video of this also (16 MB Quick Time - BE PATIENT):

http://www.gametomorrow.com/minor/barry/julia.mov

This is the third time the link is posted to the video in this very thread, lol. Thanks though. 3 times the charm, i'll look at it in a few second.

**wrathofall** · 03-26-2006

Oh my God! I'm blind! My humble apologies.

**NUMA NUMA** · 03-26-2006

That's really cool!! And w/ no RSX

**FiNaL-FaNtAsY** · 03-26-2006

im in utter silence when i think about this capability.

**cocruxified** · 03-26-2006

Awesome............(To the Highest Possible degree) When I look at that first screen I can't help but think of something from the Matrix. Craziness.

**Lefein** · 03-26-2006

I know where that picture was taken. That's in the rotunda at the Governors Mansion in Austin Texas

**esper256** · 03-26-2006

Nobody has mentioned this. But the challenge of ray-tracing grows linearly with resolution.

1024x1024 is a gargantuan resolution to be ray tracing at. I doubt it would fare so well in a more complicated scene, but this is still insanely impressive. But texture mapping in ray-tracing is a bit different than texture mapping in raster graphics.

But after thinking about it for a bit, there's no good reason why it can't be done in raster graphics. The important thing is that with smart memory management, Cell will be able to add some very interesting post-processing effects.

**Einz** · 03-26-2006

In Cell we Trust.

this is shocking people.... OH MY GOD!!

**Ricokillercon** · 03-26-2006

MMMM...i can't wait until developers have enough time to familirized themselfs with the ps3. I can't even imagine how games will look like after 3-4 years of the ps3 life time.