Intel 980x 6-core system with 480 gtx gpu - Info and questions

[Jeanyes]

I made a simple scene with a box and sphere, vray camera, vray rectangular light.

Rendering without RT it takes 37 seconds. This is using Solid rocks "IM/LC - the default method"

With RT "CPU" selected after about 10-15 seconds I get about 1000 KPaths/s but it continues to "render" for several minutes.

With RT "OpenCL (Single Kernel) selected it steadies out to around 4700 Kpaths/s after 10-15 seconds but also continues to render several minutes.

My question, when do I know it's "done" ? After a few seconds there is no visible change in the image but because I have "show statistics" turned on I can see that it's still "rendering." Also my GPU usage is still 100%. I see others here posting render times for RT renders but I only get a status line in max when I do a standard production render. I'm probably just missing something obvious...

[vlado]

You can specify either a time limit, or a noise threshold for the RT rendering - whenever it reaches one of these, it will stop. We will also be adding a third limit based on the number of samples/pixel. You can check how many pixels are still left to sample if you turn on the "Show Mask" option.

Best regards,
Vlado

[Alan Iglesias]

Since RT uses Progressive Path Tracing (or Brute Force to Vray fans), you are "done" whenever you think the image is acceptable. It may look like it has stopped rendering, but it's really still refining the image, removing "noise", and would do so indefinitely, all things remaining the same.

Keep in mind that for the most part, RT is basically currently designed for preview and not final work, although most of us certainly would like to get there eventually, if not sooner!

In RT, you can get a definitive level of image refinement by setting the Adaptive Sampling/Maximum Noise to a certain level, and same-scene timing comparisons (different hardware, let's say) you do will now be valid, as long as the Max. Noise level is the same. I've also used this to get each frame "equally rendered" in animations.

Another way to quantify rendering "power" is the Kpaths/sec (Show Statistics), which gives you a very good read on how quickly your CPU and/or GPU hardware is rendering.

Hope this clears things up a bit,

-Alan

[marko_mandaric]

You can specify either a time limit, or a noise threshold for the RT rendering - whenever it reaches one of these, it will stop. We will also be adding a third limit based on the number of samples/pixel. You can check how many pixels are still left to sample if you turn on the "Show Mask" option.

Best regards,
Vlado

samples/pixel as a restraint would be fantastic... with enough power (read: tesla's) you'd be able to pull real realtime with a reasonable level of quality.

[Jeanyes]

Ok, I see now that it was actually still rendering... Under my normal Vray production render settings I see that my DMC Sampler "noise threshold" is set to ".01" I set my RT "max noise" to match this (it was .001 before) and the rendering times increased to just about match my production render time. Should I set the trace depth and gi depth to "1" as well? (the are at "5" and "3" by default) What settings are everyone using that gives them the extremely fast render times compared to an optimized production renderer? For me, the default RT settings are leading to render times much longer than the production renderer. I'm sure this would not be the case with more complex scenes but for this simple scene it is what happens with default settings.

Edit: Posted this and I now see that Alan gave more detail about my original question above. I see that I would also need to set my production renderer to "Brute Force" to match what RT is attempting to render.

[vlado]

It may prove hard to beat a tweaked production rendering; the irradiance map and the light cache are very powerful techniques for speeding up rendering, even though they have their own issues. As you start increasing the quality and going to brute force GI, or having lots of glossy reflections, the RT will start to gain advantage.

Best regards,
Vlado

[Jeanyes]

Alan,

You and others have mentioned the desire to turn RT into a production renderer. This got me thinking.... It's obvious that GPU's are very good a performing certain calculations quickly. Why not allow GPU's to help the regular VRay renderer with portions of the needed calculations? I realize this is not exactly what you were talking about but this would certainly make regular VRay much faster. I guess that's more of a question for Vlado...

[vlado]

Unfortunately it is not that simple (it has certainly crossed our minds ) As soon as the CPU and the GPU start waiting for each other, passing lots of data around, the speed drops drastically. With that said, there are a some things that we can indeed do in that regard, hopefully you'll be able to see them soon

Best regards,
Vlado

[Alan Iglesias]

What settings are everyone using that gives them the extremely fast render times compared to an optimized production renderer?

I think the important thing to remember here is that most folks will not be necessarily trying to match RT quality noise-wise with production Vray quality right off the bat. RT, and especially RT/GPU has the potential for you to see almost instantly most all of your lighting, shadows, reflection, refraction, etc. elements very quickly while test-rendering for adjusting the same - if not in final-render quality noise-wise. This is the initial inherent strength of the rendering system. With all the hype going around the industry regarding real-time rendering, it's easy to lose sight of this simple truth.

-Alan

[Alan Iglesias]

Alan, I guess that's more of a question for Vlado...

Yup, and his answer gives us much hope for the future!

-Alan

[Jeanyes]

Thanks for the clarifications Alan and Vlado. These are exciting times!