Spawning RBDs When Particles Collide With Geometry

[melissa]

Hey guys,

I'm new to Houdini and newer to the forums.

I am working on an effect in which I have many objects falling, hitting a plane, and where each object collides with the plane I want to spawn a few cubes. The effect is supposed to look like debris kicked up by the objects hitting the ground, but in the form of cubes. The objects are copy stamped onto particles that are falling, and I need the cubes to be RBD objects so they tumble away physically accurately.

So far I am achieving this by having particles - with polygon circles copy stamped onto them - fall until they collide with the ground. Then I am using an RBD Point Object to create a cube at each point on the circle.

My problem is getting each set of RBD cubes to be spawned when the particle collides with the plane.

I activated "Add Hit Time Attribute" on the Collision POP and have the HITTIME attribute transferred to the circles. I bascially want the Creation Frame on the RBD Point Object to be the HITTIME, but this will not work. (By the way, the RBDs spawn just fine if I put in a random Creation Frame # or $F. Getting them to spawn separately, at the right times, is the issue.)

Any suggestions? Thanks!!

[melissa]

If it helps, attached is my file. I had some sticky notes for myself, so hopefully they are helpful.

Please note that the Creation Frame here is "20", so all of the cubes are created then.

RBDsFromParticleCollisions.hipnc

[Ryan]

Hi, Melissa. Welcome to Houdini and to the forums.

I looked at your file and it looks like you are doing really well.

All you need to do is create a group in the Collision POP. That group will contain the particles that hit the ground at that frame and only that frame. In other words, they will not stay in the group forever. And then, in SOPs, you can isolate the particles somehow.

Then in DOPs, when you use $F, your boxes should come in at the right time.

Hope I was clear.

Edited February 3, 2012 by Ryan

[melissa]

Thanks!! That worked!

To anyone who is interested: I added a Collision Group on the Collision POP called "hit", then used a Delete SOP after the POP Network. In the Delete SOP, I used the Group "hit" and the Operation "Delete Non-Selected". Then on the RBD Point Object I made the Creation Frame "$F".

[ryew]

It sounds interesting, I'll have to take a look and give that a try to see what its doing. Thanks for sharing, Melissa!

[dyei nightmare]

wow a female houdini user... interesting and interesting solution too

Edited February 4, 2012 by dyei nightmare