Random Opacity For Instanced Particles?

[yawzer]

Hi guys,

i'm making some sparkles for pixie dust. I used point particles and instanced 3 different shapes to it. Now i'm trying to get these objects to randomly glitter on and off.

i tried creating a per particle attribute : particleSparkleShape.visRand = rand (0,1)
and then put that to the Visibility dropdown in the instancer options...

but it doesn't seem to work. i'm probably doing something or everything all wrong =p

Can anyone shed some light on how to get these things to glitter?

thanks!!

[ptb]

First of all, why not use sprites? -> Much faster, more control. Do you really need 3d sparkles?

Anyway:

First make sure you created a runtime expression, second of all you have to change the expression to:

CODE
particleSparkleShape.visRand = floor(rand (0,2))

This is because rand creates a float value, and if its between 0 and 1 all in all it neither reaches the 0 nor the 1, so you get values like 0.354 or whatever and visibility is a bool that only understands 0 and 1. So you need the floor operation to make it integer and go up to 2 to make sure that 1 will appear (else it'll only be 0).

[yawzer]

i thought of sprite but i was hesitant to make a hardware rendered pass and a software pass for some cloud particles i'm also using for the effect. I've also had trouble local rendering hardware particles and was afraid of the time it would take to troubleshoot the problem. But i'll definitely reconsider it, what more control is there using sprites?

and thanks for expression help its greatly appreciated =]

[ptb]

QUOTE(yawzer @ 11/05/07, 08:01 AM) [snapback]275968[/snapback]
i thought of sprite but i was hesitant to make a hardware rendered pass and a software pass for some cloud particles i'm also using for the effect. I've also had trouble local rendering hardware particles and was afraid of the time it would take to troubleshoot the problem. But i'll definitely reconsider it, what more control is there using sprites?

and thanks for expression help its greatly appreciated =]

With sprites, you can use the opacityPP attribute to give every sprite an individual transparency (and not this quite unpleasant on and off, but more of the flicker you'd probably want for pixie dust). I'd recommend using a ramp with fractal mapped to a color -> this will result in a random glitter effect and you can let it fade out before death, too. In addition, there's the rgbPP attribute that allows you to tint the sprites in a certain color and achieve a bigger variety of effects.

Don't use the Hardware Render Buffer to render, use Maya Hardware. But yes, it's not always easy to comp hardware passes... (perhaps you could achieve your cloud effect with sprites, too)

[petershipkov]

Particle instancer is one of the biggest problems in maya these days.
Hope somebody will wake up at Alias and add the missing bits.
For now you will need third party renderers to be able to do what you asked about.

[joojaa]

Actually its not the particle instanter node itself, all they need to implement a shading node to do this. And that is missing (because if they implement it in the instancer node you get one color and one opacity only but you will want to have it a material shading variable if possible).

NOt its not hard to make on its just a bit fo a hustle to determine the id correspondence so thst you can export the info to mr.

[petershipkov]

The particle instancer does not handle shading groups internally.

[joojaa]

It dont need to because your shading node could possible be as something with many colors if the node handled the shading then you would need many materials or many shards of instances. if you just have a shading node to read the data thats enough. Because the shading network can handle this internally just like back face coloring, all you need is to expose the pp variables.

Off course you wont have screen feeedback but thets not very important sinceit could never do a normal complexity shading network real time anyway.

And you can do that allready, each instance has a unique id because each object has... so all you need is to make a correspeodence list that you look up... its just a bit convoluted to do it properly with sane work flow but amaya api does provide all the information you need. Now all you need is to populate a node witha array of corrspodence and array of values.

So basically what you want is a switch node that has the correspeondence table. This all in itself is not a hard thing to do its just not done for you. But you can do it yourself.

The only api functions you need are described in deopnstrative instancerListCmd wich can be miodified to get each instancers instances id. And by that all the hard part is done now all you need is to output this array to custm mr node/maya hading node.

And then you are set.

[dryodryo]

OK, so it's super easy! Maybe you have a few seconds to hack one out? Surely it wouldn't take longer than writing a forum post describing how it's done?

[joojaa]

Well i would if it wouldnt sound too much like work.

Besides i really can't. FIsrtoff i dont have extra ID's but thats just a excuse i could allways use test level ids. But more prominently it could be seen as breach of contract, and that would cost me more than years salary easy.

But im happy to hack it for you were you open to pay for all my possible legal and salary losses. BUt im pretty sure you cant afford that.

[dryodryo]

So, some company owns you and everything you do? Your contract states that you are not permitted to work on any freeware or open source projects on your off time? If that's the case, I would suggest you rectify that situation when it comes time to renew your contract.

[joojaa]

QUOTE(DoctorYo @ 11/08/07, 10:39 PM) [snapback]276217[/snapback]
Your contract states that you are not permitted to work on any freeware or open source projects on your off time?

No it just states i cant do stuff that i sold to somebody else as part of contract after the fact for a said period of time. Which is pretty normal. However nowhere does it tell i cant tell HOW i did it. I can however sometimes under some conditions sell it again.

Im free to participate in open source projects as long as its not directly the same thing. So not to confuse my commitments. So nobody can say i copied code from where i sold it. Irrespectibly if i did or didnt does not matter, it just looks bad and tahts all it takes.

Its like a animator selling the same piece of unique client animation to 2 clients as exclusive.

[dryodryo]

So in other words, you've already done it, but it's proprietary code.

That's the problem with capitalism, isn't it? Contrary to popular belief (especially in the USA), competition sometimes stifles innovation.

In the words of Ivan Sutherland, information is one thing you can give away and still keep.

[joojaa]

QUOTE(DoctorYo @ 11/09/07, 10:50 AM) [snapback]276240[/snapback]
So in other words, you've already done it, but it's proprietary code.

Yes. Problem is that people pay for comparative advantage! I would gladly do everything is do open, however the contractors don't see it that way. So if they were to decide that this would be worth 1/10 of the pay that would mean i get paid 1/10 wich would mean id need to either find 10 more people to pay for this wich in turn turns to longer time in sales wich turns to less profit wich menas i need more people. Problem is that even i need to get money to live. Which aint so cheap as i need about 1500-2000 euros after taxes to get by. And i dont want to work all that long hours, so that i have time to do something else that does matter. As often those paid for projects are just for some kind of marketting hype factor.

On the other hand i don't see open opensource totally perfect either since open source has tendency to put too much stuff, and too unplanned, into something.

QUOTE
That's the problem with capitalism, isn't it? Contrary to popular belief (especially in the USA), competition sometimes stifles innovation.

Sometimes? Id say allmost allways. BUt ist a problem of human networking more. Since not only do we spread good habits but also bad ones. So in the end what wins over something else isnt decided by inovationess, usefullness, understanability or whats better. But rather by chance.

PS unfortunately there will always to end of time be properitary code, unless we can assimilate all information into one mind (ala borg). But then theres properitary between humans and something else.

[dryodryo]

There's a difference between "unpublished" and "secret".

[joojaa]

Its not seecret, its nit complex either. Its not really a innovation as much as just a very simple reading the implications of the manual. (unlike what you think not all implications can be written down, because i know about 1000 implications to a hammer and i seem to come up with new ones every second i think about it, and a hammer is very simple and i could spend the resto fmy liffe cataloging each and every use for a hammer)

And i told you with very clear instructions how t do it, in fact maya software can do this with a expression (and that also isnt a seecret its a perfecty published feature, in fact i first saw this on maya 2.0, offcourse t you need api for corrspondence but if random is ok you dont need even that). But because mr cant use expressions you need to write a simple sjhader that can take a array if ntegers and turn it to some other stuff. Very elementary code the shader is about 10 lines long.