Laguna

Show-off, reference material & tools.
UnRAVeL
Posts: 4
Joined: Wed May 09, 2012 6:42 am

Laguna

Postby UnRAVeL » Wed May 09, 2012 6:57 am

Hi, I made a little OpenCL pathtracer. Check it out at http://www.geeks3d.com/20120502/laguna- ... th-tracer/

beason
Posts: 48
Joined: Sat Dec 10, 2011 1:58 am
Location: Los Angeles, CA

Re: Laguna

Postby beason » Wed May 09, 2012 8:40 pm

Nice. Do you have a video? I'm confused by your timings. When you say 12 FPS for 1080p, do you mean the final image quality is achieved 12 times per second, or the window is progressively updated at 12 FPS? Do you have some ray/sec stats? How many rays or paths per pixel in the 1080p frame? Do you have any full-res screen captures?

UnRAVeL
Posts: 4
Joined: Wed May 09, 2012 6:42 am

Re: Laguna

Postby UnRAVeL » Wed May 09, 2012 9:16 pm

Fps is calculated on the time spent raytracing one frame with 1 sample per pixel (default).
Here a picture of a render on a nvidia gtx550ti: Image

beason
Posts: 48
Joined: Sat Dec 10, 2011 1:58 am
Location: Los Angeles, CA

Re: Laguna

Postby beason » Fri May 11, 2012 2:20 am

Very nice, thank you. That image took about 1340 samples / (4.08 frames/sec) * (1 min/60 sec) = 5.47 minutes to produce, I take it. Seems quite fast!

UnRAVeL
Posts: 4
Joined: Wed May 09, 2012 6:42 am

Re: Laguna

Postby UnRAVeL » Wed May 16, 2012 9:38 am

I still can't figure out why the performance on a 7970 is only marginally better compared to a 680, I expected the 7970 to be much faster. Does this mean my kernel is compute bound? Can anyone shed some light on this?

Dade
Posts: 206
Joined: Fri Dec 02, 2011 8:00 am

Re: Laguna

Postby Dade » Thu May 17, 2012 7:00 am

UnRAVeL wrote:I still can't figure out why the performance on a 7970 is only marginally better compared to a 680, I expected the 7970 to be much faster. Does this mean my kernel is compute bound? Can anyone shed some light on this?


There are profiling tools available both for AMD and NVIDIA that can help you. The AMD profiler has a counter that tell you the ALU utilization, it is a good indicator if your application is compute bound or not.

However, in my experience, ray tracers on GPUs are far from being compute bound and are instead mostly driven by register/cache size, cache/memory bandwidth, etc. The 680 is supposed to have some limit in the cache/memory bandwidth/size so the 7970 is usually faster.


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