rgbPP question

[Als]

Why not use multiple emitters?


Als

[bluehonda]

yes, i can use multiple emitters. but i hope, it can still be done with the right expression.

[kbrown]

Don't use ramp. Simply in your trail particle's creation expression do this:
seed(id);
float $R = rand(1); float $G = rand(1); float $B = rand(1);
rgbPP = <<$R, $G, $B>>;

[shanshore]

Hi.
Each trail to hv different color of ramp...

Assuming particleShape2 is the trails particleSystem and
particleShape1 is the source particleSystem,

step-1: particleShape1 to hv rgbPP attr and use rand function in creation Expression to hv different colors of each particles...particleShape1.rgbPP = <;

step-2: particleShape2 emits particle trails, to get the same color as its parent...
add parentId attr for particleShape2 (if ur not sure, it is found in particleShape2 -> Add Dynamic Attr -> General (button) -> Particle (tab) -> parentId)
use this creation Expression for particleShape2...int $par = (float)particleShape2.parentId;
vector $rgb = `getParticleAttr -array true -at rgbPP particleShape1.pt[$par]`;
particleShape2.rgbPP = $rgb;
which gives different color for each trail (but not a ramp)

step-3: gradually changing the color to white to get the ramp using this runtime-expressionparticleShape2.rgbPP += <<0.03,0.03,0.03>>;

I got the different color ramp for each trail.
lemme know if u dont understand / trouble with any part of this...

- Shanshore

[bluehonda]

woow! thats awesome shanshore. exactly what i need. thanks to everyone!

bluehonda

[MikeRhone]

Interesting... I have a different approach to the problem. I try and avoid using MEL in a particle expression whenever I can (getParticleAttr)... One of the coolest tricks out there is to use global variables in particle expressions. I set the attributes I want on the source particle, and have that information passed down to the particles that get emitted to it. So here is how I do it:



Add rgpPP to both particle systems, and add parentId to the trail particle.

//sourceParticleShape Creation Expression
sourceParticleShape.rgbPP = <<rand(1),rand(1),rand(1)>>;
global vector $PartColor[];
$PartColor[ (int) sourceParticleShape.particleId ] = sourceParticleShape.rgbPP;


//trailParticleShape Creation Expression
global vector $PartColor[];
int $pid = trailParticleShape.parentId;
trailParticleShape.rgbPP = $PartColor[ $pid ];


I use the quite often to pass along a rand value from the trail particle into the lifespanPP on the trial particle. Each particle in this 'comet' system will have tails of varying lengths. Nifty trick, eh?

[shanshore]

nice idea mike. This global variable helps a lot to optimize the performance.

I hvn't thought abt it so far.

- Shanshore

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