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Distance Field AO: Vegetation Issue

I was trying out the distance field AO and noticed something a little strange when painting trees, that one of them was a lot darker than it should have been. I looked in the visualize thing and saw that only the first tree that I painted was getting the effect. Is there a way to enable it for them all, or to disable it for them all while still using it for the rest of the map? It seems a little counterproductive to have an AO solution like this for dynamic lighting and then have it break on instanced objects like this.

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asked Jul 29 '14 at 12:55 AM in Rendering

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avatar image Jacky Jul 29 '14 at 01:08 AM

Even though this seems like a bug, i dont think DFAO will work right with meshes like trees currently. :\


Limitations of the technique

DX11-only, high end feature Non-uniform scaling cannot be handled correctly (mirroring is ok) Only Ambient Occlusion is provided, which is different from Sky Occlusion because it has a limited blocking distance Only casts shadows from rigid meshes although they can move dynamically Materials that deform the mesh through World Position Offset or displacement will cause artifacts, as the distance field representation does not know about these deformations

Limitations of the current implementation (can be improved in the future)

Only static mesh component is supported for now. In the future, other types may be supported that are also rigid. Meshes must be mostly closed. For example, a box will work, but a plane will not. However, if the material assigned to the UStaticMesh asset is two-sided, both sides will be treated as front faces and the distance field will be valid. The mesh must be rebuilt to propagate a change to the material applied. Surfaces without a distance field representation cannot receive occlusion yet and get a constant occlusion of .5. This includes skeletal meshes, translucency, static meshes with CastShadow disabled or that were not closed, etc. Updates to the AO from dynamic scene changes lag a bit as the work is spread across multiple frames. Occlusion may shift around a bit as new samples are generated. Seams between modular meshes - lighting is done using the Distance Field normal, which is curved around hard edges. This causes seams in the occlusion between otherwise flat surfaces.

Regarding all this you may want to skip DFAO for now if your project requires too many trees.

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