Global Illumination on the GPU

Get a sneak peak at the next GPU acceleration from nVidia for mental ray here (scene courtesy of Tai-Jen Su)

Notice in 9 minutes the GPU accelerated version is already complete while the non-GPU version has only completed the top left corner with similar settings.



About David

I am a VFX artist that specializes in Lighting and Rendering. I spend a fair amount of my time supplying clients with artistic solutions as well as technology solutions. With a background in fine art and technical animation training, I strive to bridge the divide between the artist and technologist.

Posted on October 18, 2013, in Optimization, Uncategorized and tagged . Bookmark the permalink. 24 Comments.

  1. Looks promising 🙂 How does nVidia plan to compete with other GPU renders on the market so it takes off with a bang ?

    • nVidia already has a GPU solution with iray. mental ray on the other hand can offload certain tasks to the GPU that benefit. This would hybridize mental ray but not make it a GPU renderer.

  2. So instead of creating something that can compete with the modern GI system like the ones in Vray, Arnold even 3Delight now.., we will have the same 10 years old crap Final Gather system, just on gpu?
    Cant hold my breath.

    • This isn’t the same thing as regular FG on the GPU…but we’ll have to wait for more.

      FG rays trace the light path towards the light and/or other objects, point to point. This is a path just like a “path tracer”. You can explain these interactions as a Light Path Expression. Calling these rays anything from “path tracing” to “final gather” is essentially the same thing: sending rays into the scene to sample other objects and lights along a path. Brute force Final Gather sends rays along these paths.

      Just like Subaru has All Wheel Drive and Audi has Quattro. Different names for similar technology.

      But something no one else is doing is using the GPU to send those rays. For example, would you rather use your 4 core CPU to send 100 rays or 1000+ cores to send 100 rays?

    • Look at it like this simply(naming aside which I agree is unfortunate)

      -Path tracing traces a path from the camera into the scene. This ray bounces off of objects until it terminates at a light or a specific trace depth
      -Final Gather rays trace a path from camera (eye ray) to object to object (diffuse or specular bounces) in the scene and terminates at a light or after exhausting the trace depth.

      Final Gather may or may not introduce interpolation into this. But it doesn’t have to in order to work. If you omit interpolation you have essentially what everyone is doing for rendering: shooting rays along a path.

      Now, in rendering in systems like Arnold we often have pixels with thousands of rays in the resulting image statistics using a technique like “path tracing”. And few things are better for shooting thousands of rays per pixel than a GPU.

  3. Ok that’s great so how do you do it, maxscript, string option, …? I want to know the process so I can try it too. I read that optix is built into mental ray so how do we make it use the gpu to offload some of the processing? Also can you use multiple gpus?

    • Optix is used by mental ray for both Ambient Occlusion on the GPU as well as Global Illumination on the GPU. (The Optix presentation at SIGGRAPH mentions these features.)

      However, only ambient occlusion is available in mental ray 3.11. Global Illumination on the GPU was announced for mental ray 3.12 at the SIGGRAPH user meeting.

  4. do you know when it will be released? How did you get access to it?

  5. I’m pretty excited about seeing a feature like this. Each node on our farm has a dedicated Tesla k10 GPU. It would be great to use the interpolation of the mental ray standard mode combined with brute force of the GPU. This will bridge the gap for alot of users who are reluctant to move from CPU only renders.

  6. look great, but anyone knows how can send it “GI GPU ON” Network rendering, because i submit a scene with the value “ON” but the value is off always.


    • Are you using a string option manually or through the mel script provided on the NVIDIA forums? Also make sure you have it as type “string” and not “boolean”

  7. CPU Rendering won’t disappear overnight, although compared to the cost of GPU nowadays it is losing it’s spotlight. GPU are costing the same if not more then some of the CPU on the market today.

  8. I agree ! Game Engines are becoming like Render Engines, in the end not all will survive !

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