View Full Version : making particles avoid an obstacle

05 May 2008, 02:16 PM
Ive got a particle system where particles randomly move along a surface avoiding collision with each other. I need to be able to place geometry on the surface which the particles avoid.

I tried to do this by placeing a nurbsCircle around the objects and comparing the position of the circle and the particles taking into concideration the radius of the circle. Then I dried to make the particles to avoid the area that the cricle covered. How ever I cant really get this to work.

If anyone has got a good way of how to achieve this.. preferably with expressions.

Thanks a bunch!

05 May 2008, 04:42 PM
how about to cheat it with field, place volume field to ur obstacle. It should looks like avoiding it. but no self-collision.....of course.

05 May 2008, 04:12 AM
I would use a field like Don3Don suggests, but take it one step further and have the obsticle object be the field. Like a radial field, make it effect the partilces then select the field and the object go to the >Fields menu >Use Selected as Source of Fields. This will make the object the field, you can also use this on particle to create fake paricle collision.

06 June 2008, 08:54 AM
thanks for your replies. The problem is that I am using goalU,goalV to move the particles along the surface. And that overrides the fields. I can use the force from a radial field emitted by the obstacle and with an axpression have them move around it. But if I want to have a large number of obstacles I need to be able to make some kind of array to include them all. such as all the objects with a name starting with obstacle will be included in the array.


06 June 2008, 02:42 PM
I should imagine (I can't test now) that you should be able to use .position(U,V) and set direction(speed, magnitude) vectors with a ramp - C=X1, M=X-1, Y=Y1, K=Y-1, where your surface is "painted " with your obstacles. I remember Tom Klyskens did a demo of this for Weta & LOTR "massive" (perhaps in an Alias siggraph masterclass video?) (before it was massive).

Another way may be to use wire, or wrap, or sculpt deformers to deform your surface (and thereby your parametization) on one object, then "Shrink Wrap", or flatten your mesh. But this, I guess would be dodgy.

06 June 2008, 11:28 AM

Thanks for your reply. Ive been working with other projects but am now back trying to tackle my particle problem.

Big Sky.. you wrote
you should be able to use .position(U,V) and set direction(speed, magnitude) vectors with a ramp - C=X1, M=X-1, Y=Y1, K=Y-1, where your surface is "painted " with your obstacles.

Could you explain a bit further on how you can take the CMYK data to manipulate the direction vectors. Cant get my head around it properly.


07 July 2008, 04:12 PM

the same problem with me praticle obstacle if u find this problem pls tell me its very urgent


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