Change color on each collision

[drGonzo]

Heya -

First of all, excuse my silly questions, I am coming from 10 years of Maya and I am going through growing pains with Houdini.

I am trying to get particles to change color each time they collide. So every time they collide they should get a new random color.

I have them change color on the first collision using a collision group and color POP but after that I am stuck.

Can any one provide some suggestions?

[johner]

On the Attributes tab of the Collision POP there's an option to "Add Num Hit Attribute" which keeps track of the number of times a particle collides with something. Giving each particle a random color based on a combination of it's id and numhit attributes ($ID and $NUMHIT local variables) should do it.

[old school]

Here's an example file that shows how to randomly color points by $NUMHIT.

It also shows how to color points based on the hit surface point color as well. This latter method requires you to create an attribute mapping for the 3 float vector hitCd.

color_particles_by_numhit.hip

[drGonzo]

Excellent! Thanks guys. Much obliged.

[drGonzo]

Old skool,

how did you change the color of the nodes? That is very handy!

[drGonzo]

how did you change the color of the nodes? That is very handy!

Never mind, got it ;-)

[wiz79]

Ah yes the ole numhit color change.. This makes me nostalgic and happy =)