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Blowing Hair

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tim
Blowing Hair
by
on Sep 2, 2005 at 4:41:34 am

Basically I'm trying to find the best way of blowing Hair quite fast (my character is falling through the sky).
I've tried using wind with some turbulance and would be fairly happy with it if the animation were slow motion. I can't seem to get the illusion of falling at a fast speed with that method (or maybe I'm missing something in the settings of the fields).

Any help would be majorly appreciated.


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Jason Brummett
Re: Blowing Hair
on Sep 2, 2005 at 2:20:36 pm

Sometimes during when Dynamics just won't give you the look of what your after, I resort to lowering the render quality settings then rendering out 2x or 3x as many frames, then tweaking the frame rate in Post. It's hackish but sometimes the easiest and quickest result...:)

Jason Brummett
Studio Z Inc.


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Steve Sayer
Re: Blowing Hair
on Sep 2, 2005 at 3:47:09 pm

Jason's approach sounds like the right one to me.

The thing is, when hair is being blown that strongly, it's really being snapped and yanked around very quickly and very chaotically; computed dynamics tend to be better at more gradual, smooth motion.

In fact, the best approach might actually be to forget about trying to simulate the motion with realistic forces (Air, Turbulence, etc.) and find some other way of animating the hair so that it pops and flicks around randomly. Maybe expressions, or maybe animating the random seed values on the hair or something along those lines.

-Steve


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Sean Fennell
Re: Blowing Hair
on Sep 2, 2005 at 6:39:39 pm

you could try layering two noises. One at a standard frequency and a second with a very high frequency and slightly lower magnitude. Also remove all attenuation and actually animate the noise field moving through space which will give you a fourth dimension to the noise.

Those couple of things could really get some turbulent wind. And failing all of that, you can do something slightly more advanced:

select your hair system node and break connectons on the 'time' attribute. then keyframe the time attribute (or place an expression) that progressed twice or even three times faster than maya's standard time. This will make the simulation actually move 3 times faster while using the old simulation settings. You might have to cache the hair dynamics before doing this.

This is how we used to do time adjustments to particle systems that were a little too slow or a little to quick.


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tim
Re: Blowing Hair
by
on Sep 3, 2005 at 7:20:25 am

Thanks guys.. some great ideas.

Only problem with animating the time attribute is that if the head is moving about then the hair is going to reach it's position before the head.

And I think if render out 3 times as many frames then bring it back in post it'd start to make an inefficient working method as I'd be animating the character for slow motion then speeding up everytime I want to do a playback? Unless I've misenterpreted your idea?
I guess I could render the head and body seperately and scale all the keys out 300% on the head when it comes round to rendering..

I like the sound of Steve's idea of using expressions somehow. Can anyone point me in the right direction for this?
Or any other ideas are much appreciated.

thanks again


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Steve Sayer
Re: Blowing Hair
on Sep 4, 2005 at 9:00:43 pm

[tim] "Only problem with animating the time attribute is that if the head is moving about then the hair is going to reach it's position before the head."

I don't think that's true--have you tried it?

I think that 'warping' the time for the hair should only affect its dynamics calculations, not its position relative to its source surface.

What method are you using to create the hair? Is it the hair plugin, or PaintF/X, or something else?

-Steve


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Sean Fennell
Re: Blowing Hair
on Sep 5, 2005 at 6:14:27 am

No it's true, since the cv positions in space are controlled by the dynamic simulation, if you retime the simulation node, it changes when the cv's are in certain positions on the hair geometry and that won't sync up to other animation in the scene. The same happens to particles when this technique is used, and I tested it.

However, if you used a layered approach it would work. Do the normal dynamic simulation, then use the output curves from that simulation as a new hair system. On the new hairsystem you could turn startCurveAttract to 1 and then apply a wild turbulence force. The forces will be applied to the hairs on top of the start curve positions they're following. This is a feature I specifically request from Alias and they did this one right.

More than one way to add hair to a cat...


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tim
Re: Blowing Hair
by
on Sep 5, 2005 at 2:05:37 pm

thanks again..

"On the new hairsystem you could turn startCurveAttract to 1"
Can't seem to find this though?
How new is this feature? I'm on 6.0

t.


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Sean Fennell
Re: Blowing Hair
on Sep 5, 2005 at 4:41:29 pm

yeah that startcurveattract is in version 7. Have you tried increasing itterations with your turbulence field applied? that may give you better fast wind effects, or it may just slow the hair down more.


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tim
Re: Blowing Hair
by
on Sep 7, 2005 at 12:35:11 pm

yeah it looks like hair doesn't like me very much :(

think i'll have to go back to the original "hackish" suggestion.

thanks guys


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Steve Sayer
Re: Blowing Hair
on Sep 5, 2005 at 3:59:10 pm

Oh! Sorry guys, my oversight. Thanks for the correction, Sean.

-Steve


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