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Tesselation cracks in 4.8. What changed?

So I’m getting weird adaptive tessellation cracks in 4.8 P4 (near the edges of the screen) as I move the camera around. It’s noticeable with an ocean shader with vertex displacement.

Tested Flat and PN Triangles tessellation with crack free displacement checked on and off… pretty much same result.
The same material setup worked fine in 4.7.

What changed exactly? :stuck_out_tongue: right now the only way to fix it is to turn adaptive tessellation off but that kills performance of course.

The problem can also be seen in wireframe.


As you can see, the mesh at the top part of the screen is for some reason with no tessellation (that’s where you would see the crack in Lit mode).

This can only be seen at certain camera angles (and you need to have animated vertex displacement) so I understand if it’s difficult to catch but this have to be fixed :p.

Hey TK-Master -

What type of Mesh are you applying your Vertex Displacement Material to, a Static Mesh Plane, a Landscape? Let me know so I can try to look into exact what is causing this issue for you. Also if you would not mind, please post an Answerhub bug report for this issue so we can track it a little easier.

Thank You

A scaled static mesh plane with relatively low poly count.

No problem, I can post an answerhub bug report as well (tomorrow though :p). I will try to also upload a bare-minimum project for you guys so you can see the problem easier.

Okay so here is a test project demonstrating the problem:
https://docs.google.com/file/d/0B7Z9rT16MoBoRGJFZC1iZVlPZkk/

Also here is the answerhub post:
https://answers.unrealengine.com/questions/234645/48-adaptive-tessellation-problem.html