World Displacement Transform Bug

It looks to me like this is a bug. I certainly can’t make any sense of it:

Here is the problem, Transform with World Displacement makes no sense, I get this 2 spheres out of one mess when it should be the same as it with WPO.


As color you can see the infomation that gets into World Displacment is always the same yet the result is wildly different.


A different transform is used, when TransformVector material expression is used in domain shader.
You should be able to get expected functionality using float3 custom node:

return mul(VectorInput,Parameters.TangentToWorld);

Where VectorInput is custom node input.

Overall, I don’t think that this behavior of TransformVector material expression is desirable though.

Thanks! I leave this unanswered for now so that hopefully someone of Epic looks into it.
The reason I need this is so I can deform things in other directions than just Vertex Normal up. For waves, wind effects and also to make procedural generated terrain more interesting. Furthermore this is for planets, so there is no simple up direction terrain.


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Thank you Deathrey and Davision. I also encountered the same problem, using the above code to solve. If someone encounters the same problem, this code is useful!