#1

Hallo,

I`m not great at MEL, and spend way to much time on figuring stuff out. What I would like to achieve: I`v got particles floating around in the scene, driven by forces.
I would like to query the world positions and velocity of the
particles on a certain frame, say frame 50.
Then on frame 450 I would like the particles to return to
the positions and velocity they were at frame 50.
So far I have only tried to get them back to the positions of frame 50, with out any success.
What I have is:

vector \$gPP = <<0,0,0>>;
float \$currentTime = `currentTime -q`;
if (\$currentTime == 50){
getAttr particleShape2.position;
\$gPP = particleShape2.position;
//print \$gPP;
}

if (\$currentTime == 450){

`````` particleShape2.position = \$gPP;
``````

}
Can you please tell me if I`m on the right track, and give my a nudge in the right direction.

Thanks
Jakes

#2

Are you doing this in the particle expressions editor, or somewhere else?
if it’s the expression editor, then you should be aware that local variables like your \$gPP are reinitialized for every particle for each frame, so it doesn’t store you value once the current particle is done. In order to do that you should do this:

1. create a vector per particle attribute on the particle shape (i.e. posStorePP)
2. in your runtime expression paste this:
``````
if (frame == 50) posStorePP = worldPosition;
if (frame == 450) position = posStorePP;

``````

#3

Thanks Azrail,

I`ll try this first thing in the morning. Just after I posted I realized that I should have worked with`.worldPosition.`And then interestingly enough I came across`.worldParticlePosition`reading tonight, will do some research on it. What I basically need to achieve is a bunch of bacteria like organisms that`s going to be projected on the Barberton rock in a museum. The bacteria needs to wiggle and move around over the rock and every now and then it needs to attract to a goal to briefly form a fossil like structure <like those fossilized worms and bugs you get>
Everything works fine except after I form the fossil like structure I can not get my particles to integrate back into the picture to wiggle around over the screen again to get ready to form the next fossil.

Cheers
Jakes

#4

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