Is there a way to make the ocean modifier fake foam spray? I already displace the water with dynamic paint, but I still am stumped as to how to create the foam. I'm assuming it's a particle system of some sort, but I'm not where to place the emitter or what general settings to change (I just need some general tips).
We need dynamic particle emission to do real foam spray. The foam mask in the Ocean Sim modifier was created to be ready once Blender caught up with that feature.
Once Lukas's Particle Nodes project is finished, it should allow for us to do that. http://phonybone.planetblender.org
The foam mask would be the source of the dynamic particle generation. The nice thing about the ocean mesh generated is that there are speed vectors associated with the waves, which I believe should also be able to be sampled and applied to the dynamic particles' starting velocities. Fingers crossed!
You could try using a dynamic paint modifier in weight paint mode that makes a vertex group around the object colliding with the ocean, which you could use as an emission vertex group for some particle systems.
Here is a blend file with an example setup. (Note, only worked for me with the 2.68RC)
However there seems to be a bug where the particles keep emitting from the same spot.
This is a limitation of the particle system implementation unfortunately. http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#Particles
The location of emitted particles are determined in advance now and stay fixed, so this can't be animated. There's been some working on designing an improved particle system that can handle such animations but it's not finished: http://code.blender.org/index.php/2011/03/paged-buffers-for-particles/