blowing a sandman??

[coolj]

firstly you can make ur sandman, with particles emmiting from objects,
emitter type to surface, and turn on the scale rate by object size..
then make the emitter`s speed to 0, normal speed to 0,
click play on the time slider,
you will see particles just being emited from the surface and not moving...
at a point where you feel that your sand bloke is coverd with particles
select the particles go to solvers, and hit intial state -> set for selected..

now you can go back to your emitter and turn down the emission rate to 0,

now your sand dude will move with particles sticking to him.

next bit..

select your sandman particles and add an air field to it..
animate the air field to start from over the head to the waist level
add a turbulance field as well to the particles ..
and there you go .. you get what you wanted...

hope this helps..

[Als]

Why would particles stick to the dude? They would stay were they are created, or you missed to expain something?


Als

[coolj]

well one thing was missing from my last reply,

well if the object is animated then the particles wouldn follow right!!

a simple fix is after creating an intial state for the particles , select partciles and then the object and hit the parent key.. cool fix your solved .., now the particles would move with object transform..
no need of any goal constrain..

[Als]

I think your best bet would be to use blendshape animation for the silluete.
Rotoscope it.
You can either make curve around it and rotoshope curve then use planar nurbs shape,
or just start with nurbs shape straight away.
Then emit particles from this object, and use same object as a goal for particles. You would need to bake texture in first frame on the object, and set this particles with initial state as explained above. For other frames, I would still keep emiting particles, but in less number, and comp them on the top.
You will need some goalPP expression to release particles over time, and some field to pick them up. Best field I would suggest for this is volume axis, with switch turbulence on.
Other more expensive way would be to use fluids as a field to blow particles away.
I would suggest free tutorial on gnomon which turns vase into a dust, this will give you good stuff, they used uniform field and particles with different mass.
Alternative is again stroika plugin since it supports object field, and also particles get get colors directly from texture, with lights and all...
If in hurry, you can do this with lots of lots of small polygons or triangles, by making plane soft bodie with springs, by texture maping the sequence on it, and then blowing soft bodies particles away...
You might even try to use cloth, with switched off collision detection, and make them tear, see Duncans blog on confetti...


Als

[thomwickes]

Yep that sounds good - also, add the parentU and parentV to the per particle attributes and in your particle expression set

goalU = parentU;
goalV = parentV;

This will set the goal to their point of surface emission instead of them clinging to the vertices. You'll get a random spread of particles across your surface.

[actionbrad3d]

G'day-


Another thing you could look into is craeting the silouette using aftereffects or a similar program, so you have an animated black and white map of a person walking, while black wipes down the frame, so effectively hou have an animated black and white map of your end product. Then, stick the animated map on a plane in maya and use this map as a particle generation (exact term not certain) map in your particle node. What you end up with is a particle system emitting from the plane, but only in the white areas of your map.

hope that helps a little.

EDIT- I just realised this would proabably result in the whole body emitting particles evenly instead of just from the top which is what you want, but... Hou could still use a version of this method- Use the animated map i mentioned as an alpha for a shader on the plane which looks like sand, and then make a nother version of hte map in AE, this time wiping another black ramp over the top of the animation, so you end up with a thin band "scanning" down your person walking. this would then do what you want , and yoiu could then control the particle emission properties as normal, using forces and emission rates ect.

My apologies if this is all a little confusing. i dont have time to do an example right now, but if you have any questions let me know. ;)

good luck mate. sounds like it will look cool whatever you do .

brad

[ctb]

Thanks guys from the suggestion.

ok.. let me explain a little bit more. Now, I have some foortage with a bunch of walking/running people in silhouette. I can't trace them out & make them into silhoutte geometry. It is killing me. Ahh~.. Is there anywhere to get away from roto the foortage into silhoutte geometry?? Because beside a bunch of people, there will have some building, tree, stuffs pass by in the foortage.

May be thomwickes' method works:
goalU = parentU;
goalV = parentV;

Ok, let's say, I create a plane. I make this plane is an object emitter. This emitter have mapped a file node (in its texture rate). File node will plug a running sequence of foortage in silhoutte.
Turn on Enable Texture Rate & Need Parent UV, goulUV & parentUV expression.
Make goal between plane & particle. Get the 1st frame fill up with enough particle & set as intial state. Emitter Rate set back to 0. Turn on file node's Use Image Sequence.. Now, the particle stay at where it is begin. It won't change the shape.
ahh~panic! How to make particle stick to the silhoutte form the foortage??
(my 1st question here).

2nd question is how to make this particle slowly be released.

why I want to keep back this amount of particle through the whole process, it is because, later I'll change this particle points into blobby. Render as water condensation...

Hope anyone have better suggestion...

Thanks.

[Als]

This sounds like a 2D job, with exception of the ending.

You can also create particles for every frame by using texture emitting, eg recreate them every new frame, and just animate some field to knock the out of the place...

Or you can use illustrator or coreldraw to get geometry of silluets for the first frame, and animate them from there on by yourself.

You could also try maya own convert -> texture to geometry?


Als

[Als]

Open image file in Illustrator CS2, Object -> Live trace -> make, take of fill, put line stroke, edit as you wish, save as illustrator v3, then import in maya, rebuild curve to the same number of points, create plane nurbs object, blend shape with existing one, continue until done, what's the problem? :)
You can batch trace files using Bridge and Live Trace as well.

Use mel to automate on the maya end?

Just an idea...

If you post like 10 frames, I might give it a shot...


Als


PS
Maybe Photoshop CS3 Extended migth be able to do what you need?

[ctb]

Thanks everyone here for trying to help out.

Because of P&C, I can't send out the images. But, I found a way to cheat that.
I use after effect to animate blur (ramp blur). After that export as bitmap & work on realflow. In realflow, use bitmap emitter. Let the particle die every frame, which replace a new particle every frame. ...

Ayway... thank for suggestion.

Have a nice day!

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