Particle copying instead of instancing animation!?

[jana-bergevin]

Is there any way to make a duplicate of your object at the particle position instead of an instance? The problem I'm having is that I want my character (which is animated with trax) to be used in a crowd scene in which the characters are doing different actions. This is impossible with instancing as all the characters would have the same animation. Does anyone have any ideas? The only other thing I can think of is to duplicate the character and apply an expression to each of them individually instead of to the particle. Please help!

[thnkr]

Please log a feature suggestion with Autodesk. This stupid limitation has annoyed the hell out of me for years, but hasn't gotten any attention because (and this is true, I checked) "not enough people complained about it". So go complain, please.

[joojaa]

Yes you can do this. You could have done this as far as maya 1. So no no such limitation.

Thing is tough, people often look at particle instancing and say that its a sort of limitation its not. Its attacking a whole other set of problems, namely need to have LOTS of objects about. See the thing is having a particle copier (this should be called BOIDIZER) is as slow as having a copy in first place! So for the same reason as you feel uncomfortable having 100 copies of your rig in the scene you will feel having 100 copies in first place.

Ill make a example as soon as i get a new gfx card.

[joojaa]

OK got a new gfx card so i can start with this. My computer feels a bit sluggish because my bios went and the raid is re-builduing sheesh!

I must do this in installments because doing this on one go would make me mad. Fisrt thing you have to realize is thet you dont want to use a particle system to control your boids, unless you have some exacting reason to. Ill try to list a few reasons here.

1. You have a working particle animation going on and you need to spice it up. In this case your using the particle system as a offloading proxy for the really heavy stuff.
2. Allmost like above but you PLAN to use the particle system as proxy.
3. You have at least 30-50 entities you need to control
4. You need to use the array samplers facilities. Or some other perticle systems cached values.

One interesting reason that does not affect the decision one way or another

1. you need copies born during playback. Well the particle sytem does you no favors here. Neither does the api or even the ENTIRE MAYAS CORE DESIGN. It is literary as hard and slow in all the cases. More on this later tough

In the next post i will try to illuminate how you can do the exact same thing as particle system without bothering to use it in the first place. Thing is its often just a feeling you have that you ought to be using it. But since it doesnt give you any benefit you should not do so.

[jana-bergevin]

Thanks for your replies and sorry for my late post. I think I might have stumbled upon a script that could help, but as I have yet to try it out, any advice is still appreciated! Please elaborate Joojaa! I'm curious as to how you'd go about implementing a crowd sim without a particle system.

[joojaa]

Im comming there but im still bit busy

I'm curious as to how you'd go about implementing a crowd sim without a particle system.

Have you seen any good  crowd sims with one?

[jana-bergevin]

Well if you were doing a simplistic crowd sim in which you only have a few different characters that were doing some sort of flocking behavior (birds/fish) then I could see doing that with a particle system, but I need to be able to have my characters doing different trax cycles not all doing the same motion.

[joojaa]

So make one copy per particle in the instancer. In actuallity you never need them all in same fidelty you juat think you need it.

Say you have 3000 humans all doing several things, well yes, but wouldnt 3000 humans doing 100 induvidual things fool the user equally well. Well it does. This is why the instancer exists, outside thsi scope its of no use. However once you reach the point whereeach particle instancer is 1 object you gain nothing form using particles. You just loose something. Speed performance and gain.

Now why do people THINK they need particle isntancing. Well for starters beccause they are not programmers and they think you can not have loops in expressions. It turns out they are wrong. Thing is tough the expression node is a extremely limitted compiler. But if you realize that it is actually justr a preprocessor for expression specific syntax it start suddenly making sense.

Thinking something si what you need is different form what you really need.

So you can have loops in expressions. You just nee to tell the preprocessor what the hell it is you mean. In actuallity you could omit this if you would write your own preprocessor. But thats just semantics. the fact is wether or not you type it its how it works. So what does the preprocessor look for, it looks for connection definitions. So let us provide it to the system, lets make a cool thing that has allmost no practical use whatsoever. I call it string of beads:

create 10 (nurbs) r=1 spheres on the -z line with a separation of 2.4 units form each one before make a expression (set evaluation to on demand this speeds up things a bit):

//pre processing statement 1
vector $position[];
$position[0]=<>;
$position[1]=<>;
$position[2]=<>;
$position[3]=<>;
$position[4]=<>;
$position[5]=<>;
$position[6]=<>;
$position[7]=<>;
$position[8]=<>;
$position[9]=<>;
//eof prprocessing 1

$numberOfItems=size($position);
//iterate each solution x times this make sfor a better solution
for ($oversample=0;$oversample<10;$oversample++){
for ($item=0;$item<$numberOfItems;$item+=1){

//drag the next sphere to 2.4 units off its predecessor
if ($item>0){
$dif=$position[$item-1]-$position[$item];
$position[$item]=$position[$item-1]-unit($dif)*2.4;
}

//push aside any collisions
for ($a=0;$a<$numberOfItems;$a+=1){
if ($a!=$item){
$dif=$position[$item]-$position[$a];
if (mag($dif)<2)
$position[$a]=$position[$item]-2*unit($dif);
}
}
}
}

//pre processing statement 2
$temp=$position[1];
nurbsSphere2.translateX=$temp.x;
nurbsSphere2.translateY=$temp.y;
nurbsSphere2.translateZ=$temp.z;
$temp=$position[2];
nurbsSphere3.translateX=$temp.x;
nurbsSphere3.translateY=$temp.y;
nurbsSphere3.translateZ=$temp.z;
$temp=$position[3];
nurbsSphere4.translateX=$temp.x;
nurbsSphere4.translateY=$temp.y;
nurbsSphere4.translateZ=$temp.z;
$temp=$position[4];
nurbsSphere5.translateX=$temp.x;
nurbsSphere5.translateY=$temp.y;
nurbsSphere5.translateZ=$temp.z;
$temp=$position[5];
nurbsSphere6.translateX=$temp.x;
nurbsSphere6.translateY=$temp.y;
nurbsSphere6.translateZ=$temp.z;
$temp=$position[6];
nurbsSphere7.translateX=$temp.x;
nurbsSphere7.translateY=$temp.y;
nurbsSphere7.translateZ=$temp.z;
$temp=$position[7];
nurbsSphere8.translateX=$temp.x;
nurbsSphere8.translateY=$temp.y;
nurbsSphere8.translateZ=$temp.z;
$temp=$position[8];
nurbsSphere9.translateX=$temp.x;
nurbsSphere9.translateY=$temp.y;
nurbsSphere9.translateZ=$temp.z;
$temp=$position[9];
nurbsSphere10.translateX=$temp.x;
nurbsSphere10.translateY=$temp.y;
nurbsSphere10.translateZ=$temp.z;
//eof prprocessing 2
Ok so the processor statemenst make the code look messy but you the user can ignore them all you need is to inject them after your edit so theres no reason you need to worry about them. in fact saying ist bad coding practice is a bit stretching it, a lot of this kind of autimatic injection does happen even in better systems, just as long as its hidden its not hindrance.

Drag the first sphere see the others follow it but avoid collision

 Ok so this has a problem it does not remeber the starting state so inject:

if (frame==1)
for ($item=0;$item<$numberOfItems;$item+=1)
$position[$item]=<>;

before the last preprocessor. Note im not moving the number 1 sphere because im reserving you keying its position so you should key also the initial state. If you want better it easy to extend the service of initial state to the objects themselves.

This is for how to do massive expressions easily with very little effort WITHOUT particles. Now in next post i can expand this  a bit. You can get much better.

PS: sorry about the new board mucking the layout of the scripts so they are a bit hard to read when you paste them just indent them again.

[joojaa]

Oh by the way this gets the properties of particle simulation in thet it needs to be baked befroe sending to farm, and only works at playback etc etc. After all we just left the land of determinism.