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POP Acceleration Limit

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luanrogalewski
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4 posts
Joined: 9月 2024
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hey all!

I need a way to limit the acceleration of each particle in a POP net.

I can't seem to find a way to accurately calculate the change in velocity of the particles.

Any help is appreciated, thanks in advance!
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animatrix_
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4729 posts
Joined: 2月 2012
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Hi,

You can do it like this:

Store old vel:

v@oldv = @v;
i@has_oldv = 1;

Limit_acceleration:

if ( i@has_oldv )
{
    vector dv = @v - v@oldv;
    float accel = length ( dv );
    float maxaccel = ch("maxaccel") * @TimeInc;
    
    dv *= maxaccel / accel;
    @v = select ( accel > maxaccel, v@oldv + dv, @v );
}



I used this method in a lot of RBD sims on Aquaman destruction shots and LOTR: Rings of Power bridge destruction. Works a lot better than POP Speed Limit DOP.
Senior FX TD @ Industrial Light & Magic
Get to the NEXT level in Houdini & VEX with Pragmatic VEX! [www.pragmatic-vfx.com]

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