View Full Version : Particles: Suggestions on transforming water to ice?

06-13-2003, 12:58 AM
I've been working on this for the past two days now with little luck. I've tried several different approaches, which I'll list and try to keep everything as organized as possible.

The shot basically is a water sprinkler that gets blasted with a freeze ray, so I have to go from water particles, to some kind of freezing transition, and end up with ice in the shape of the sprinkler spray. It's for a 2d / 3d cartoon, so it doesn't need to be very realistic, it just needs to look cool :D

My first step was to create a NURBS plane and scale it way out to act as the ground. Then I created a volume particle emitter and set:

Transform Y: 2
Rotate Z: -30

Speed along axis: 20
Spread: 0.1
Rate: 5000 particles/sec

Lifespan Mode: Constant
Lifespan: 5.0
Render type: Tube
Radius 0: 0.1
Radius 1: 0.5
Tail Size: 0.5

Then I set the particles to collide with the ground plane and added a default gravity field.

So the water seems to work fine, the transition and ice stages are giving me problems though. I'll start with the ice and then work backwards to the freezing step.

I attempted to create static particles based on my above emitter settings and was able to get a shape I wanted and keep it at frame 0 (thanks cgtalk search fuction) but for some reason at around frame 65 or so they would flow backwards into the spot where the emitter was, so 60 frames later, no particles. So I put that aside and just modeled a rough shape for the final ice in sub-d's and converted it to polys.

I had two thoughts on the freezing step. I could set up a curve to cut through the middle of the ice shape and have another curve animate along the first with path animation. I could then make curve2 a goal for another emitter and with the goalu attribute (I think that's right) to make the particles flow around curve2 as it follows the path set by curve1 thereby creating a guide for an opacity wipe from water particles to ice geometry / particles. Problems arose there when I had to key frame the opacity ramp, I'm apparently missing a step or two because everything works if I key straight opacity for the object, but when I set keys for the ramp nothing changes.

The other idea was just to use that rough geometry to emit particles to simulate the freezing, thus emilinating the need for keyframing the ramp. I set the ice geometry to emit and had them go to a goal (locator inside the geometry), but I also set the geometry itself to be a collision object (thanks Jozvex :)). By this I hoped to get sort of a bouncing off the geometry / radiating freeze effect.

That's my closest effort and it still looks bad, although partly because there are a few things I can tweak, but it still won't look all that great I fear. I realize this has been a bit long winded, and you have my undying appreciate just for reading it :)

I've also played with surface flow just a tiny bit, but to me it looks like that would give me a much too organized flow (well, with as little as I know about it anyway)

So, if anyone has any suggestions, or corrections to my listed methods I would greatly appreciate any comments. You would be my hero for at least a week or so, teehee :cool:

Thanks in advance!

06-13-2003, 07:12 PM
ok after several more hours of work...

I have the initial volume emitter for water. This one is being affected by a default gravity field and a ground plane acting as a collision object.

I play it out to the desired frame and keyframe emision rate, speed, and gravity to 0.

At this point I swap in a duplicate set of static particles for ice, because I can't seem to set a key for conserve, which would (I think) stop the particles from moving and allow me to use one set through the process. As it stands now, the particles would retain their velocity and float off into space (since gravity is keyed off).

So I go from moving water particles to static ice particles.

All that remains is some kind of 'freeze' transition. I'm thinking I could select the static ice particles and have those emit particles of their own, to create sort of a smokey vapor effect. This works fine and dandy until I want to key frame the emision rate to let the vapor clear.

So now I need to know if you can key frame particleB's emision rate where particleA is the source, and if that's possible, what I'm doing wrong. :D

I'll keep working at it, but if anyone happens to know the answer to my problems, I would really appreciate the time you could save me :)


06-16-2003, 02:52 PM
ok, I've figured this one out :applause:

For those of you keeping score out there...

I've got 4 particle shapes in total.

- water particles
- freeze ray particles
- 'freezing vapor' particles
- ice particles

Once it was time for the water to freeze I just keyframed the water emission rate, gravity magnitude, and water particle's conserve values. That gave me the motion to static effect I wanted (or close enough, it would be better to slow them to a stop from source to tip of spray, but I can't figure out how to control velocity ramps).

At the beginning of the freeze sequence, I keyframed a NURBS sphere at the source, and moved it along the path of the water, keying translation and scale. I had that object emit particles to act as smoke / vapor being produced as the water froze.

While that happened, I had the water particles emit particles of their own since when water freezes it expands.

Sample Video (http://www.hromikarenders.com/movies/spinklerFreeze.avi)

This is a rough sample render of the effect. My particle shaders are way off, the incandesence is waaaaay too high, but that can be fixed for the specific shot.

12-09-2004, 01:09 PM
i can`t see your sample video ...

CGTalk Moderation
01-15-2006, 09:00 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.