[Sidefx-houdini-list] POP particles rotation situation here...

Javier Meroño javiermerono at hotmail.com
Thu Jul 14 04:21:51 EDT 2011

Here´s an interesting one I just bumped into.

I want to add several (different) rotations to my POP particles. I 
noticed you can´t chain several Rotation POPs: it only applies the last 
one. My best guess being the reason for this is the Rotation POP assigns
 the actual rotations to the particles, just like the velocity assigns 
velocity as opposed to being a force that adds to it.

Hence, I go for the Torque POP, which indeed does work and allows several of them to be concatenated as they are forces.

BUT, obviously I want to limit the Torque to one or two frames. 
Otherwise it adds up every frame and I get too much angular velocity. 
The problem being my particles are "activated" by putting them inside a 
group which is preserved.

I solved the situation by adding another non-preserved group that activated the torque force.

Is this how you usually deal with several rotations?

Also, I would like the angular velocity to to get increasingly higher as
 the particle moves more, so I add an angular velocity node and use 
something along the lines of 


which more or less works, with the exception of one or two particles that would require some "individual" love.

All of this seems a tad messy and unelegant to me. How do you usually 
deal with this....do you go the VOP POP route? Just trying to understand
 how it is usually done in big productions....


Javier Meroño 		 	   		  

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