Help with complex POP effect

[DavidRindner]

Hi, this is my 1st post and I am looking for help.

Let me 1st describe the POP effect.

Car is moving (Object animation) towards camera (camera is motion control)

stops, camera pans to the side of the car, the car drives away. OK that was the easy stuff.

The car is moving through rain, and replusing the rain particles. However, its replusing them in special way. As rain particles approach the car they are repulsed but ONLY towards -Z direction, which towards the rear of the car. The animation path of veichile is along +Z. As particle is replused it makes a 90 degree tigh radius turn, then flows along the contour of the car towards the rear. After it completes its journey, at the rear end of the ccar, it is picked up by gravity and falls towards ground. But its more complex then that. The rain particles that are repulsed around center of the car start their contour journey from the center. The ones in the from from the front. So any given particle only starts its contour flow from where ever it is repulsed from the surface. Do you see the complexity.

I have already went through so many POP tries, so I know what won't work. If anyone is thinking of a CreepPOP, forget it. It can't work for this effect. Even if you can determine the UV point that is repulsed the particle , the state switch is sharp, where as I need smooth turn of the particle. I have concept sketches of pop flow. If you email me at daverindner@yahoo.com, I can send them to you. Any help is highly appreciated. I am stumped.

Thank you

Dave Rindner

[michael]

would the new Particle Slide features help at all?...you could model the 'shapes' of the flows you're looking for and the particles would slide along them, then off and be affected by gravity...

I haven't really done any POPs so...

anyway I hope this helps a bit

[anakin78z]

I don't really think I'm getting what you're saying, but another thing you could check out is the softlimit pop.

One thing you might want to look into is how sony did the face splash in hollowman.

What you could do is run your simulation on a flat plane, which will be much easier to controll, then map it back onto the car. you could create a velocity vector field based on the 'slope' of the car, so that partcles don't just flow straight over the flat plane. When particles reach an edge, and would fall off the car, just use a split to birth a new one which then falls to the ground.

Something like that.

[betty]

very rough simple car travelling through rain.

mmmm, very rough....is this like anything you were after? i'm sure you could play with this and come up with something, though anakin'z idea about remapping it onto the car from a more controlled flat surface sounds good.

carinrain.hipnc

[will]

halo david,

thanks for the reference images. try out the attached hip and let me know if that is/is not what you were going for. if not, what can be fixed or changed?

will

carpops03.zip

[betty]

nice one will,

i just saw the new beta 6 POPs video last night of the new parameters, ie cling and dynamic friction and thought - "wow! that's cool!....that's how i could i could 'clean up' that hip i posted."......nice job!

you suprised me that you had both the 'cling' and 'dynamic friction' set to 0? i thought this would then not return a result....

and thanks, you reminded me that it helps if the vehicle is somewhat aerodynamic, silly thing to overlook.

[Stremik]

Just a wild guess.

Make a copy of the car and blow it in size(proportionally) just a bit.

This, bigger car will not be rendered.

place a smaller car inside the bigger one and than use the outer car as an path for particles.

[DavidRindner]

Thank you all for your help.

However, my 5.5 fails to load both of your projects correctly. A myriad of 'Skiped...' errors are generated. So if you built it in v6 I can't really use it. Did you guys use custom VEX or some ciustom plug-ins.

Anyhow, we found a Maya based solution, that works pretty good. My work is now limited to camera matching (in Maya), and doing CG splashes in Houdini. For CG splashes I baked the particle simulation into BGEO sequence using Geometry ROP.

Found that a good way to do volume curve flow effect is to have a striaght stream of particles. The bake them into geometry sequece using Geometry ROP. Bring back that geometry into Geometry using File. The use LatticeSOP to contour the particle flow. For liquid effects, just use the particle flow point as template source for metaballs. That is append it to CopySOP and use metaball primitive as instance object.

Dave

[will]

thanks betty

the new particle sliding can turn out some very useful effects! concerning the dynamic friction and cling set to 0- anytime i am playing with particle sliding, i setup both properties and then adjust the sliders until it looks the way i expect. in this case, that turned out to be at 0 and 0. when you say not return a result, do you mean just returning a result of zero?

whichever the case, what i have come to discover with pops is that numbers in an absolute sense don't mean too terribly much. what is more important is how they are relative to each other and the scale of the project.

will