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View Full Version : Particle Dispersion then Re-formation. HELP


adityaprabhu
07-03-2006, 05:09 PM
Hello everyone at CGtalk. Im new here, been using 3DS max for a few months. Ive gone through Allan Mckay's tutorial on particle flow dispersion from an object.
I wanted to use it in an effect im working on..
Its like this.. I want the object (say Teapot) to disperse into fine dust, maybe fall to the ground (Gravity) and then slowly move towards another point and gather and build up from there slowly to form another object (Say a Pyramid or something)
Now, the first part of dispersing the object is achieved.. Then, i did the following:


Age tested the particles which are on the floor to some amount.
New event: Find target> the new object. (i need help with refining this pls)
New event: Position Object (for particles to occupy space on the new object surface)..I need help here too to start the particle occupation from bottom to top.
Slowly Fade the particles and bring the actual Geometry to view.
Im looking forward to being one among all the CG artists here.
Waiting for a tip on how to solve this.
Thanks

adityaprabhu
07-04-2006, 05:35 PM
Anyone? Any ideas? please pool in!

thanks

supremepizza
07-04-2006, 09:13 PM
You can start on this thread. http://forums.cgsociety.org/showthread.php?t=376148

Same thing only different.

For the rebuilding there's a discussion about building a structure brick by brick from the ground up with particles. I think it's burried in the monster thread sticky above.

adityaprabhu
07-05-2006, 04:43 AM
Im taking a look at the thread now, thanks!

adityaprabhu
07-05-2006, 11:10 AM
Ok, i checked the link, couldnt find the right answer im looking for...
i cant even post the test renders to give you guys any idea becos of the size limit..

Also, how can i use motion blur with particle flow? Object motion blur is too damn slow with mental ray as well as scanline.. what options do i have?

psy_med
07-06-2006, 01:48 AM
I've been playing around with a way to achieve a similar effect to what you described and ive come up with a way that seems to work quite well.

In order to get the particle to go onto the surface in a certain way you can use a find target in combination with an object that has a "deletemesh" modifier and a "volume select" modifier or two on it. By using the volume select to select certain parts of the geometry and then the delete mesh to get rid of it you can cutout all the geometry you dont want the particles to go to.

An easy way to do this is just animate the volume selects's gizmo to move upwards so it reveals the geometry. Just make sure you have the "deletemesh" modifier above the the "volume select" or it wont work.


Hopefully this helps and sorry if it doesnt make much sense, ill try and explain a bit better if you dont understand when ive had a bit more sleep.

CapitanRed
07-06-2006, 10:42 AM
I never tried that, but i think, you could try it with a speed by surface. and combine that with some ''compositing''. I think about the same way as your disperese, just the other way round:)

lets say, your particles are on foot. and move to one side. when they find their target, the move to the speed by surface, and move along it continuosly. when you have a lot of particles, they will build the shape of the object.

in the same time, the object is transparent. make a gradientramp in the opacity mapslot. and make it go from bottom to top, from black to white.
this will make your object get visible from bottom to top.
in the same time, make a deflector go from bottom to top, which sends the particles to the next event. in this event, the particles get smaller(scale operator), and die after some frames.

I hope you get the idea.

I never tried that, but it could work i think.

adityaprabhu
07-06-2006, 11:52 AM
Ok, firstly,

psy_med: This is something that could definitely do it for me, will give it a shot when im with Max. thanks.

secondly,

CaptainRed: Hey there, This is exactly what i did ( the opacity map with gradient ramp animated flags) but i dint use the speed by surf operator, i will try it again with the suggestions. thanks!

Here are some renders at frame 0, 100something and 250. the remainig half or the build up of object two takes place at the right and is yet to be rendered.

Tell me what you think uptill now. (Im looking for a space that lets me upload my files, where can i do this?)

CapitanRed
07-06-2006, 01:29 PM
http://forums.cgsociety.org/showthread.php?t=256465here are some places where you can host your files.

adityaprabhu
07-06-2006, 02:20 PM
test render of the first part (low quality)http://www.megaupload.com/?d=FTNCPVY7

CapitanRed
07-07-2006, 03:43 PM
looks nice. try that with GI:D

I tried to do particle dispersion with vray. there the probleme is that you can not just turn down the opacity. there is no opacity:shrug:
so, i tried it with matte/shadow(material wrapper in vray materials) and some compositing work.

I did one vray render with the object. one render with a gradient ramp from white to black, and one with particles and matte shadow material on the object.

and then i composed, and used the black/white render to key the vray render. and over that, i puted the particles render.

the only shitty thing on that method is, that all the particles, which are emitting on the backside of the object, are not visible, because the matte material. so, looks little strange.

perhaps someone does have an idea how to get it look right?
I don't know, but is the opacity working with GI in mental ray?

adityaprabhu
07-07-2006, 05:33 PM
I don't know, but is the opacity working with GI in mental ray?

thanks..
Yes, its working fine for me with mental ray. The still renders above (a few posts above) were infact done with mental ray, opacity and final gather. But didnt try GI. Will try and let you knwo...but i think it should work since final gather didnt pose any problems.

Also, you might wanna try out the Delete mesh combined with Vol.select modifiers to do it without opacity... (as psy_med suggests,)
Dont think it would give a controllable result though.

psy_med
07-08-2006, 03:13 PM
Hey adityaprabhu, those renders are looking nice.

I have played around a fair bit with using opacity ramps to disperse or build objects. The great thing with using this technique is that you can get away with a lot less particles as well as the end result generally ends up looking a lot more whole becuase its acutal geometry rather than a large amount of particles. The bad thing however is that its so fiddley and annoying to make changes to, the whole system really isnt that procedural.

As far as just doing the effect in reverse and then just taking it into a compositor, that does work for simple effects but if you want to have multiple dispersions and other effects it really does get anoying have to piece together the seperate effects in a comp, Not to mention that working in reverse can get frustrating.

Ive found that doing a couple of tests with a volume select and delete mesh really work quite effectivley. You get a lot of control and you can work in just Max rather than having to jump into your compoistor to see what the overall effects is looking like.

Here is a quick render i did with that technique
http://s76.photobucket.com/albums/j2/psy_med/?action=view&current=test01.flv

adityaprabhu
07-09-2006, 05:50 AM
Hey psy_med, firstly, call me Adi (just to make it simple and short), anyway, the render is nice! The effect seems to be happening preety fast so i couldnt exactly see how the particles line up, but can you give me a procedure how you did that (if you dont mind)?
Also, i've been looking everywhere to get good looking motion blur on particles using mental ray...any ideas?
Which renderer do you use?
thanks...

psy_med
07-09-2006, 09:58 AM
Hey Adi, Im glad you like it :)

The technique i used to do the sequentially go onto the objects is the one i explained in my previous post. By just using volume selects and a deletemesh to force objects to only display/have available specific points of the geometry at any one time you can control. ive attached the file that the render is from, hope this helps. You will need max8 to open it however.

I dont have that much experince in the area of motion blur. I usally just stick with the scaneline render's image blur as its quite fast and doesnt look to horrible. From looking at Cebas site and the little bit of playing around ive had with it Finalrender stage 1's motion blur capabilities seem to be really good but im happy with the scaneline renderer's speed.
http://www.finalrender.com/products/feature.php?UD=10-7888-35-788&PID=36&FID=301

adityaprabhu
07-09-2006, 07:19 PM
Hey thanks a lot for the scene... checking it out when i get to my Work pc..
Will keep posting if i get some newer ideas...
regards,
Aditya

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