View Full Version : Sticky particles along a surface

08 August 2008, 02:31 PM
I'd like to ask a question about particles. I'm trying to create two effects:

1) having particles flow down an object preferably under the force of gravity (or something that looks like gravity)- the typical surface flow goalU goalV trick on a nurbs mesh wouldn't work since I want the effect to happen on an animated polygon mesh

2) any idea for having clumps of particles drop from objects, like drops drop?

and in the end I'd like to have those combined - some drops flow down an object and drop when they reach the end of the object.

Any suggestions ?


08 August 2008, 02:45 PM
the only thing i can say now is .. try maya 2009 ;) hehe it must have some sick particle systems

08 August 2008, 12:51 AM
The Kolektiv have a good tutorial DVD - Particles Visual Effects Series - which includes getting drops to slide along a the surface of a soda can and then to run onto another surface.

The Maya Techniques - Flow Workflows also has a good example of drops flowing from a pitcher and falling away. I don't know if this is still in print, but if you can find a copy it is worth checking out.

08 August 2008, 09:17 PM
There is a technique that I have used before...I think it comes from the dvd Meesto mentioned (alias maya techniques - Flow).

Basically the idea is to goal the particles to a nurbs object and create a closestPointOnSurface and a pointOnSurfaceInfo and attach them to the surface. Then for particles you'll create a gravity attr and a slope attr. In the runTime expression you get the particles position + your gravity attr value and feed that into the closestPoint node to get where the particle would be...then set the goal of the particle to that. Then for the slope you can get the surfaces normal from the pointOnSurfaceInfo node and once it reaches the value you set in the particle slope attr the particle will un-goal from the surface...meaning if you surfaces curves at the bottom and the normal of the surface starts to point down or away the particles will release and fall with a gravity field......if any of this makes sense. Its a pretty cool technique once you see it. Ill attach a test scene file I set up. Hope this helps.


09 September 2008, 08:43 AM
Thanks, I've found your setup very useful. I'll have to give it a try on a polygonal mesh. While I was still trying to solve this problem I've was wondering on using normal field and non 1.0 goal value - it gives me enough space to use diffrent fileds on those partilces and using normal gravity intead of an artificial one that is given as an attribute. Additionaly using uniform instead of gravity would give different "flow speeds" based on partilce mass. The only thing that has to be "worked around" is having fields magnitudes PP based because such strong fields that "flow" particles down an object look bad when particles "drop" from object.
Thath would be it conserning particles flow down an object.

Thaks again.

09 September 2008, 08:11 AM
You can use parentU and goalU on poly meshes without any need to setup the CPOS nodes if you like. To vary speed of each particle just assign a random mass and offset that to the goalV runtime expression. You can then set goalPP to 0 whenever the particles reach a certain height in Y. The only problem is if your animated mesh decides to rotate or deform so that the direction of goalV becomes horizontal, you'll lose the effect of it looking like gravity.

09 September 2008, 09:34 AM
I think I'll stick to closestPointOnMesh (using poly mesh not nurbs) method since it gives me the ability to have gravity pointing downwards.

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09 September 2008, 09:34 AM
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