[Bf-committers] Proposal: Blender OpenCL compositor

[Aurel W.]

> DOF and Blur you can take care of with overlapping source tiles as long as you know the maximum fetch distance (the blur radius, basically). Takes a bit more memory but it means you can parallelize them pretty much how you want (with diminishing return because the overlap zone size is constant).

Hi, there are many nodes, where this won't be easy, and they really
need "full buffer access". Just computing overlapping patches for a
simple convolution case gets far too complicated and is really not
flexible at all.

Let's assume you have filter node, with a lot of iterations, so
several convolutions taking place. The patch based approach fails
here, since you would need to access also the updated regions in the
other tiles, which were computed by an other patch. The only solution
is to grow the the overlapping areas depending on the number of
iterations.

Let's assume we have a convolution node as DOF, which does several
iterations and has a long graph as an input node. Essentially the
patch size has to be changed each time the you adjust a setting in the
node and therefore the entire sub graph has to be evaluated again.

Changing patch sizes? That doesn't make sense to me and really gets
overcomplicated. Full buffer access is needed in this case as I
pointed out previously. There are also other operations, which need
access to the entire buffer to determine a single pixel.

Again, I have a very bad feeling about this patch based approach.

aurel