2012年3月6日 星期二

Tessellation has cracks


what is crack?
- visible seam btw edges in the mesh
  - often color variance
   - shareds vertex deiverge position


Can cause hole without tessellation
Domain shader interpolation between tessellation

Ebsure the domain shader is using same input data ( pos, uv, normal)


Implementing AEN
Method1: index buffer
 - add extra index
- point to adjacent edges
- average normal in shader

Method 2: texture
 - store average normal
 - load() in shader

Displacement map cracking
-UV coordinate are discontinuous
-Historical issue for texture mapping
- displacement offsets along shared edge

Solution: Dominant UVs
- override UV for sampling displacement
-interior primitive

Imp. dominent UVs
-method1: index buffer
-method2: texture

Intra-naterial cracking
-Meshes in games often mule materials
   - submeshes render as separate draws
  - with separate textures and UV spaces
 - no access to neighbor info


Virtual Dicing
- Tessellation factor limit of 64
    - 1 edge => 64 edges

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