Hello all, my first post here...
After doing some reading of this board, I'm assuming this is a question for Duncan 
I want to use the Ocean shader for a wide shot of a river in it's later stages (i.e. when it gets to a bay/sea)
I have a couple of questions:
Do I need to make all my terrain collide with the ocean? Is it just cosmetic, or are there benefits to the simulation by doing this?
How to get flow?
Looking at a lot of reference I can see how river flows in late stages have interesting and varied flow patterns. I really want get these flow patterns. I am also hoping that they will help a lot breaking up speculars/reflections in a real way
What would be the best way to get flow? Wakes? Textures? (I thought about doing some wind tunnel fluids to get textures for flow, what would I then affect with theses textures?
I have had a look and can't see any immediate answers to these questions on the board, also, I come from XSI mainly and there is a very real chance this will go back to XSI for shading and rendering when done.
Any pointers greatly appreciated.
_pete
Depending on exactly what you are after you might be able to get the general flow patterns using a 2D fluid (probably a texture) with the navier strokes solver. You could collide the 2D fluid with the ground( note that the height of the fluid( sizeZ ) should be small, as collision is determined in 2D, and all geometry inside the fluid bounds collides. (you do not want the river bottom to collide). You might check out the windTunnel fluid examples to see how a steady flow is set up with expressions. Note that the fluid density would not necessarily map to wave height in these cases. There are weird things one might do.. enable coordinate grids then run the simulation a bit and set initial conditions. Now make the dynamic grids static, so they no longer animate and connect the outUV on the fluid texture to the input uvCoord on a texture placement for a water texture. This would essentially smear the uvs used for texturing the water around the geometry. You could then simply animate the offset u or v of the water to move it down the river.
A less automated way to do something similar is to simply push the cvs of the water surface to create flow patterns around geometry, then map the water as a 2d uv map.
Duncan
Duncan,
Thanks very much for that.
Here's where I am at:
Firstly, the 3 shots I am doing are very wide (almost panoramic) so pin-point collision is not too important.
I have set up 2D fluid with the terrain and run that with collision. The incandescance is using speed as input and the ramp is 6 colour (hot > cold = slow > fast).
The flow patterns are beautiful and I have noticed that they even follow the natural erosion patterns of the terrain.
I have another scene with the ocean shader set up and waves to my liking.
I now want to use the fluid (flow) sim to affect the ocean shader and actually see a river flowing. Am I crazy in thinking this is going to work?
Thanks again for your help, it is all much appreciated. I'll let you know the film as soon as I can
If you like the flow patterns you can create a fluid texture with the same settings as your fluid node and texture various attributes of the ocean shader. The critical one for waves is the oceanShader.waveHeightOffset.
It may be best to set up a wake on the ocean(this creates a texture) and modify that.
Duncan
Thankyou very much for your help, Duncan. It truly is a great service you do this community.
My experiences with maya fluids have been great. I also found reading all the Fedkiw/Stam papers at Stanford helped a lot. Once again, thank you.
Could you post a link for those papers please?
http://graphics.stanford.edu/~fedkiw/
Go to the bottom of the page to find the research papers...
hth
