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Question Graphics.Render* API in CommandBuffers

Discussion in 'General Graphics' started by Per-Morten, Oct 15, 2021.

  1. Per-Morten

    Per-Morten

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    I just noticed that we've gotten new render functions in the Graphics class, such as Graphics.RenderMesh and Graphics.RenderPrimitives. Is support for these functions planned for CommandBuffers as well?

    (I already asked about this in the beta forum but didn't get any response, and this subforum seems more appropriate)
     
    Per-Morten, Oct 15, 2021
    #1

  2. JarkkoUnity

    JarkkoUnity

    Unity Technologies

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    Hi Per-Morten,

    There is currently no plan to implement these functions in CommandBuffer. The new Render functions operate in higher level potentially issuing draws in multiple passes, while for CommandBuffer draw commands you explicitly specify the pass. There are some new functionality though (namely multi-command draws) that may in some form eventually find their way to CommandBuffer though.

    Cheers, Jarkko
     
    JarkkoUnity, Oct 15, 2021
    #2

  3. Per-Morten

    Per-Morten

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    I see. That's a shame. When I saw the Graphics.RenderPrimitivesIndexed function I was hoping we could finally get a way to render using index buffers that didn't require indirect rendering.
     
    Per-Morten, Oct 18, 2021
    #3

  4. watsonsong

    watsonsong

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    Hi, I wander to known the difference between 'DrawMesh' and 'RenderMesh'.
    It seems only to pack the parameters into a struct. Is there any functional difference? What is the purpose of the new 'RenderXXX' APIs?
     
    watsonsong, Oct 18, 2021
    #4

  5. JarkkoUnity

    JarkkoUnity

    Unity Technologies

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    @Per-Morten Does DrawProcedural work for you (takes index buffer as well)?

    @watsonsong Correct, many of the parameters are now passed in RenderParams struct for better maintenance to avoid duplicating the draw functions every time new functionality is added. From the top of my head there's at least control for renderingLayerMask and motion vector rendering added to the new functions. The Indirect functions also support multi-draw, which is currently implemented as issuing draw for each command, but for improved performance we hope to provide hardware MDI implementation in the future that's supported by many platforms. For RenderMeshInstanced you can also pass custom structs, which in addition to defining instance object->world transforms allows you to control for example per-instance renderingLayerMask
     
    JarkkoUnity, Oct 18, 2021
    #5

  6. Per-Morten

    Per-Morten

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    Unfortunately no, I didn't formulate myself properly. We not only need the ability to draw via an index buffer but also to be able to specify index count, index start, instance count, etc. Essentially, the same stuff that we can get today via the indirect arguments in CommandBuffer.DrawProceduralIndirect. Ideally, we would also be able to not supply bounding boxes and skip Unity's frustum culling as we do that on our own. So, essentially, a CommandBuffer.DrawProceduralIndirect but the DrawArgs are supplied on the CPU, not on the GPU. :)
     
    Per-Morten, Oct 19, 2021
    #6

  7. watsonsong

    watsonsong

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    I have a quest about the multi-draw support. The multi-draw method(RenderMeshIndirect), the parameters 'commandBuffer' maybe store on the GPU side. Is that means the cpu read parameter from a gpu buffer and issuing draw for each command?
     
    watsonsong, Oct 22, 2021
    #7

  8. JarkkoUnity

    JarkkoUnity

    Unity Technologies

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    No, we just issue several indirect draws with increasing offsets to the commandBuffer, so no CPU readback is needed.

    Cheers, Jarkko
     
    JarkkoUnity, Oct 25, 2021
    #8