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motorsep
Inspiring
March 29, 2016

Clipping and culling geometry outside of frustum (on mobile) ?

Does UE4 clip and cull geometry outside of frustum (on mobile) ?

Imagine a 100k tris mesh, which is only partially in the view. Would UE4 only render triangles in the view, or would it render entire 100k tris mesh ? (on Android/iOS)
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    4 replies

    vrdaveb
    Inspiring
    March 29, 2016
    See https://community.arm.com/groups/arm-mali-graphics/blog/2015/03/09/mali-performance-5-an-applications-performance-responsibilities
    motorsepAuthor
    Inspiring
    March 29, 2016
    Sounds like it will draw entire mesh if the bounding box is in the view :/
    motorsepAuthor
    Inspiring
    April 1, 2016
    Ok, so since Mali-T760 is tiling GPU, it culls based on bounding box around geometry. Understandably, chopping up meshes into small chunks (using common sense though) would help performance, since chunks outside of the view won't be rendered (assuming its bbox isn't in the view).

    However, what I wonder about is how bbox is generated around geometry. If my geometry is at 0 0 0 of the scene, and I export it into UE4, bbox will be generated around geometry at 0 0 0. However, what happens if geometry is offset and is away from 0 0 0 of the scene? Does UE4 (or GPU) makes bbox only around actual geometry or does it take into account center point of the object? (please see image below)


    motorsepAuthor
    Inspiring
    April 1, 2016
    Epic responded: https://forums.unrealengine.com/showthread.php?106051-Question-about-culling-geometry-on-Mali-T-760-(Galaxy-S6)
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