Hello,

I want to generate particle inside a Translating/deforming geometry.
But when I use I collision POP, half of the particle just pass through the object as no collision object exists.
I worked aroud that for a week but I didn't fing the solution. So, I grouped and killesd the particles that passed through but I would like to enderstand why some collied and some don't :?:

Well , Let me know guys what you think about that.

Thank you

I assume you just added numhit attribute to any particle colliding with the boundary and then using the Group POP and a rule $NUMHIT > 0 and killed the group?

Ya, the collision POP is not full proof yet….

hey Daek

under ur collision pop, under hints, make sure that u have specified that it is translating geom.

and then depending how fast its moving, try under the actual pop network, specify that oversampling is more than 1, ie 4.

hope this helps

aracid

>under ur collision pop, under hints, make sure that u have specified that >it is translating geom.

Do this first!

>and then depending how fast its moving, try under the actual pop >network, specify that oversampling is more than 1, ie 4.

This will change the amount of times per frame your simulation is evaluated. If your collision is moving quickly, it may be moving through points in-between frames, and those points are not colliding because your simulation is not evaluating in-between frames. Taking your oversampling level up to 4 or higher will give you more accurate collision results.

ALSO…. If you can, triangulate your collision geometry. When all else fails triangulating your surface can certainly help. You can triangulate a surface many ways… one is procedurally as you're building it. The other is to use a convert sop and convert your mesh to poly and turn “triangles” on under connectivity.

If you have polygons already though, triangulate using a default Divide SOP. Sometimes, better results might be obtained by using the TriStrip SOP which converts it into triangle strips and then converting that back in to polygons.

TRANLTING GEOMETRY was on but it wasn't working. I increased COLLISION TOLERENCE to 1. it is much better but I still loose some particle. Even By using DIVIDE SOP.

Anyway. It is much better now …

Thank you for your help.

And that's with increasing your oversampling as well?

Initially you mentioned that you were using a translating/deforming geometry. Using a hint of “Translating Geometry” will work well if the only motion of your geometry is a translation. Rotations, scales, and point level deformations will not work well. To handle these better you should specify a hint of “Deforming Geometry” which uses a different algorithm (albeit one that only works with triangles).

Whatever type of motion you have, you should generally always triangulate any polygons before the collision pop since any other polygons may be non-planar, and thus result in more leaks.

The Collision Tolerance generally allows collisions to be detected further from the surface. A value of 1 seems pretty high unless your collision geometry is fairly big.

Thank you guys for your advises