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danethomas
10-23-2007, 07:19 AM
I've had a look through the forums and through my books bu I can't seem to find an answer to this one.


I've using a 3d fluid container to simulate snow blowing across the ground, however the ground is quite undulating. Is there a way to deform or displace the fluid sim plane/grid so it matched the geometry of my scene ground plane, therefor I can keep the container nice and low and still have 'snow' blowing across all of the scene's ground geometry.


Thanks.
Aikiman
10-23-2007, 08:30 AM
You cant change the shape of the 3D fluid and would have to make your ground a collision object with your fluidshape. If you have a lot of voxels below the ground plane Im not sure how you would have maya calculate those above it only. Maybe use a closestPointOnSurface node and anything above that calculate density and velocity, but if that is possible, it would probably be even slower.
Duncan
10-23-2007, 03:42 PM
Perhaps you could use a fluid texture 2d mapped to transparency on 1 or more duplicates of your ground offset upward.

Duncan
Als
10-25-2007, 11:26 PM
Why 3D fluids must be in cube containers?
Is there a way to "connect" result of one to the other, so that we can for example connect more containers to build different shape?
Very often I also feel it would be great to have sphere container, which would work from minimum radius to maximum... for earth atmosphere etc.


Thanks


Als
Duncan
10-26-2007, 04:45 PM
Fluids can only simulate with regular grids. However it is possible to assign a fluid shader to any of the volume shapes (sphere, cube, cylinder, torus, cone ).

Here is a tutorial describing using a fluid for a planetary atmosphere:
http://area.autodesk.com/index.php/blogs_duncan/blog_detail/a_fast_and_simple_planetary_atmosphere/

Also you can assign a fluid shader to geometry, although it doesn't work that well. In particular.. the far length of the rayspan is a fixed distance(there is a hidden attribute on the fluid to set this distance, although I can't remember it offhand) through the fluid rather than the far side of the object and the self shadowing is still computed on the cube bounds, not the object bounds.

Of course it would be great to have arbitrary fluid shapes. We have examined various stitching and hierarchical container methods, but not yet implemented any. Jos Stam has a Siggraph paper where he stitches 2d fluids together on surfaces, using sub-d geometry. So, for example, a sub-d sphere has 8 fluids stitched together in a cube topology.

Duncan
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