[Sidefx-houdini-list] Point Instancing Animation

Agent Xray xray at agentxray.com
Mon Aug 14 11:31:44 EDT 2006


In addition to motion blur I'm also refering to having each instance be 
a loop/sequence of animated .geo files whose playback speed is 
determined by the particle velocity... and then get the proper deform MB 
on top of that.


Dan Seddon wrote:
>> Yea, I was looking for some kind of per frame instance attribute but 
>> couldn't find it. Seems like the "render from archive" feature only 
>> works from Object level.
>> The other problem with the method I sent to Jaideep is that it 
>> doesn't take velocity into account. In many cases it might be 
>> desirable to play the animation faster or slower based on the 
>> particle velocity. While it's possible to set up inter-frame geometry 
>> blending at the SOP level, I'm not sure how to pass the information 
>> from the POP up to the referenced SOP.
> Ahh.. I ran in to this as well, but it is solvable. Essentially you 
> are instancing "objects" so the only m-blur that is appropriate is 
> Transformation-Blur, it does do this, if you were to put $FF in to a 
> transform sop you'd get the result you'd expect. The problem with 
> particles is that they don't give you subframe positions so the 
> shutter breaks and you might then want to cheat the velocity as you 
> mentioned - the solution to which is to build them yourself by adding 
> the velocity back on to the position multiplied by you're time offset 
> i.e.
> In a point Sop $TX would become:
> $TX + $VX/$FPS*($FF-floor($FF))
> and the same for $TY and $TZ.
> Cheers
> Dan
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