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Microdisplacement; adaptive dicing introduces interpolation errors in the rendered view
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Description

System Information
Win10 64 bit; 24 gigs RAM; third-gen i7 CPU; ATI 79xx GPU

Blender Version
Broken: hash a0c1876
Worked: never

Short description of error
When you enable the rendertime dicing in the subsurf modifier (for displacement), the rendered view will show interpolation errors between the various patches (the F12 render meanwhile seems to be relatively unaffected). This also does not happen when displacement is being used without dicing.

Exact steps for others to reproduce the error
Open the .blend file and switch to the rendered view

image

blend

Details

Type
To Do

Event Timeline

This is a limitation of the subdivision code, which currently doesn't preserve adjacency info for patches and thus cant generate proper normals at patch boundaries. This is only a problem when the "true" displacement method is used, as "both" will calculate normals from bump mapping and doesn't need adjacency info. This should also not be noticeable if the dice rate is high enough (1 micropoly per pixel) as then the artifacts become too small to see.

This will be fixed eventually, but I haven't decided how best to handle it yet.

Sergey Sharybin (sergey) triaged this task as Normal priority.Aug 9 2016, 11:20 AM
Brecht Van Lommel (brecht) changed Type from Bug to To Do.

Marking this as a To Do item since this will still be an experimental feature in 2.78.

I guess this is somewhat similar to T49049 where averaging positions rather than normals could help.

Brecht Van Lommel (brecht) renamed this task from Exp. Microdisplacement; adaptive dicing introduces interpolation errors in the rendered view to Microdisplacement; adaptive dicing introduces interpolation errors in the rendered view.Aug 24 2016, 8:37 PM