[Sidefx-houdini-list] Point Sop

Erik Zimmermann ezim at d2.com
Tue Oct 23 20:10:12 EDT 2007

1) The Force tab on the Point SOP adds point attributes to source 
geometry which are used by the Attractor POP. Putting $VX*2 would set 
the attribute to be twice the velocity in x.  Scaling or modifying the 
velocity attribute in SOPs will not affect the particle motion, just 
velocity attribute motion blur.

2) The Normals parameter allows you to modify the point normal 
attribute, which is a vector.  Not radians.  Don't really get what you 
meant by that...


gravatar at gravatonia.com wrote:
> Alrighty, two questions.  First, does the force parameter actually do
> anything. I was under the impression way back in the day that it would slow
> down particle speed outside of the actual simulation.  I have tried
> expressions like $VX*2 and such and the appearance of the particle
> placement seems to change, but once rendered the speed does not seem any
> different when render out a sequence of frames.  I have other ways to do
> the same thing, but I would like to know what it really is doing.  Second
> question, is the normal parameter in the point sop in radians...  -1 to 1? 
> If so, does houdini convert values over 1 to the equivalent location. 
> Wasn't much in the documentation on that.
> Grav
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erik zimmermann
effects artist
digital domain
300 rose avenue
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