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augustus
03-25-2003, 07:51 AM
I'm trying to make a little animation with a some kind of bottle and gaseous goes out of the bottle (what a terrific English :p ). The bottle is not a simple shape, and will be animated ( I mean character animation, not a simple rolling). I made some tests with a simple particle setup (put an emitter follows general shape of the bottle in the bottle, make particles and bottle collide, so on). My question is, do you think I'm on right way, or is there a more reasonable way? I'm trying to use software rendered particles, cos i will use raytracing. How can i avoid the pacticles exceed the bottles's boundaries? (i tried to use a smaller version of bottle to collision detection)

Sorry for my English, i hope you can understand me. :)

Octagon
03-26-2003, 10:07 AM
Originally posted by augustus
I'm trying to make a little animation with a some kind of bottle and gaseous goes out of the bottle (what a terrific English :p ). The bottle is not a simple shape, and will be animated ( I mean character animation, not a simple rolling). I made some tests with a simple particle setup (put an emitter follows general shape of the bottle in the bottle, make particles and bottle collide, so on). My question is, do you think I'm on right way, or is there a more reasonable way? I'm trying to use software rendered particles, cos i will use raytracing. How can i avoid the pacticles avoid the bottles's boundaries? (i tried to use a smaller version of bottle to collision detection)

Sorry for my English, i hope you can understand me. :)

i think your approach is feasible. the problem you need to solve is, as you point out, how to make the particles not show up outside the bottle's volume. for the position of the particles, collision objects scaled apropriately work. but using the cloud shader makes particles shading interpenetrate the bottle and particles shading _will_ show up outside the bottle.

to solve that, try rendering a matte that cuts out all the particles outside the bottle. that means you need to model (and skin) another model around your bottle, that gets a black material assigned. assign a white matte material to your particles. so when you render your particles separately and you render the matte pass you can limit the particles to the area of the bottle.

if haven't done this before, but i guess it could work. give it a try and tell us how it goes.

matthias

augustus
03-26-2003, 01:19 PM
Thank you. I'm still modeling it, but i will try with simplified version I used before. Could thickness of the bottle be another problem, or prevent the problem you mentioned?

augustus
03-26-2003, 07:50 PM
Here is a test:

http://august.f2o.org/resimler/gaseous01.jpg

There is only an air field here, so motion looks very bad.

Altough I can't see any interpenetrating here, still plannig to use masking technique, so I can use some bigger particles.

Actually I want to get cigarette-smoke look, which is much more easy -and fast- with hardware-rendered particles. For now, it's so far from this.

Octagon
03-28-2003, 08:59 PM
if the interpenerations are not visibly for whatever reason at all , dont bother about the masking thing.

for cigarette smoke you shouldnt use cloud particles, but HW particles (as you point out). try to use _lots of_ particles and make them multipoint and use motion blur.

matthias

augustus
03-29-2003, 09:40 AM
But do you know a way for reflect and refract hw particles?

Octagon
03-29-2003, 05:12 PM
Originally posted by augustus
But do you know a way for reflect and refract hw particles?

you probably wouldn't need reflections or reflections on cigarette smoke. but if you were trying to achive those with HW particles you would use instanced particles (1 face poly planes) and constrain the instanced geometries orientation to the camera (using up vector constraints in the instancer)
it's not an intuitive procedure if you dont have a script for it. but it can be done.

matthias

augustus
03-31-2003, 06:12 AM
One last question. How can I put my hardware particles "in" the bottle while compositing?

Octagon
03-31-2003, 08:49 AM
Originally posted by augustus
One last question. How can I put my hardware particles "in" the bottle while compositing?

actually i'd like to know that myself. to my knowledge it's not possible to get the exact same look as out of the renderer if all is rendered in one go.
what you could do is "sandwhich" your elements, split up your bottle in front and back and particles in the middle.
or render all on one go and render a matte for the particles to color-correct them.

compositing elements that sit in semi-transparent objects are quite challenging. Can anyone share some of his/her knowledge as how to do this correctly and most efficiently?

matthias

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