Scatter Approach Dilemma

[shrekshao]

• Scatter approach light culling in the paper:
  • execute a thread per light
  • find overlapping tile
  • write (lightIdx, tileIdx) pair
  • sort on tileIdx using radix sort, label start and end idx per tile(This step is similiar to that in Gary's proj 1)
  • // ... tile based shading ...
• Bradly's OpenGL light culling approach:
  • create a light idx buffer for each tile with a size of 1024
  • use atomAdd to get offset (i.e. address in the buffer to write lightIdx)
  • // ... tile based shading ...
• Tian Sijie's WebGL light culling approach
  • Scatter lights into tiles totally on CPU...
  • Use texture as buffers for light pos, color, radius, etc...
  • // ... tile based shading

So I feel it a little embarrassing at this time to do scatter light culling with WebGL: no atomic op, no radix sort(implement one in shader? or use cpu sort per frame?) I'm switching to gather approach, which basically launch a thread per tile, each thread goes through all the lights in the scene and check which of them overlaps with cur tile.

Let me know if you have any ideas on this...

[pjcozzi]

Worse case, we can also change this project to be a tile-based deferred shader like Yuqin & Sijie.

I would prefer not to have to do any CPU workaround that would basically kill the performance.