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Hash, Inc. - Animation:Master

Manipulating hair in the chor, gravity--and watching my PC sail out the window


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OK. Having a hard time getting this. Got a good amount of materials, both textured and simple bmps, as well as quite a few tufts of grass/hair.


No matter what I try to turn off in the chor window so I can manipulate the grass to be "blown" in the wind, my 8-core, 16gig, 660gtx machine acts as if it can't handle what I'm trying to do.


Not sure what I'm doing wrong--how would one be able to manipulate individual "tufts" of grass? Not sure how to get the frame-by-frame rendering down to the barest minimum




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  • Hash Fellow

The only way I can immediately think of to manipulate a specific hair is have some object "collide" with it. It could be a transparent object.


Hair guides are only available at patch corners. I believe those can be animated.


While testing, you can set the realtime density to something less than 100% and still get a flavor of how the whole hairpiece is reacting to forces.

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  • Admin

There are several settings that can ease the pain of particle hair.


With the 'Realtime' setting we can have the actual hair really dense but tell A:M to only display a percentage of that.


Setting the display mode to Shaded rather than Default can help you see (and manipulate) the Model rather than the hair.


There are other settings that can help but those are the ones I'm using at this exact moment.



Now as to individual tufts of grass, you could use multiple instances of the same model.


And of course, then use the grooming tools and manipulate 'to camera' so that your image looks good from that vantage point.



Added: I should mention that while working with Hair it is generally useful to work in low density and then when finishing up crank up the density to the appropriate level for final rendering.

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As a follow up to Robert's suggestion you can manipulate one single hair by turning the density down.

He is correct concerning the hair guides emanating from the corners of the patch. I've often wished I could manipulate one that was in the center but it's fairly trivial to manipulate the corners to get the same effect.


I believe those can be animated.



The sure can! I recommend treating them just like animating with key poses, breakdowns and inbetweens.


Also, keep in mind that you can drive all the parameters (or most) via image maps.

That perhaps more than any other method is the best way to manipulate specific areas of hair.

The color scheme takes some getting use to but it's well worth investigating.

Colin Freeman's online application is still operational so check that out:




On that same page (lower right) is a download link for the standalone PC application.

It operates the same as the online app.

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The above is frame 0; I'm really liking the look so far, but I'd like the weeds to sway a bit, as if in the wind (also going to want to ripple the water eventually, but one personal crisis at a time...). The issue is, if particle render is turned on in chor at all, it slows the machine to a crawl, which baffles me as cpu/mem never hits so much as 40%, but most of the time, I'm looking at the blue windows "Leave me alone, I'm workin' here!" circle.



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There are several setting you can tweak to increase responsiveness.

If you haven't tried it I'd say your Realtime Density is the first place I'd tweak.

You can also set Realtime to display the hair as 'wireframe' which can help a lot when just tweaking hair guides.


But first.... before tweaking anything SAVE SAVE SAVE under a new filename so that you can go back to your settings.

Then tweak away.


One very handy method I discovered that works in some specific cases is to extend the length of the hair (and density as well... but adjusting the length in particular was very useful) considerably in the main settings... animate that... and then drop the length back to something more akin to what you want to see rendered.


When animating, consider only animating an in/out and middle position* to begin with. There is always a risk of over animating so you want to get those key pose in first.

Then of course... SAVE SAVE SAVE under a new filename so you can go back to those settings again as you go back in to finesse again. :)


And oh, by the way, that environment is looking nice! :)




*When I say 'middle position' of course I don't mean smack dab in the middle. Stagger that key (favoring the origin or the termination key) based on the flow/force that is driving the animation.


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I should have mentioned also.... but it sounds like you know this already... make sure you aren't in the primary material settings or the Model settings for the hair material when animating. I've caught myself doing that a couple times and it's really hard to animate what cannot be animated :facepalm:

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  • Hash Fellow






First... I think you could get the same look with a much lower density of hair.


Second... tuning that with a density map might help. Would real weeds be that dense right at the border of the patch-of-weeds? Wouldn't they be thinner at the edges and get denser in the middle?


Third... alternatively, you could use a density map to make the front row of weeds dense and the interior less dense with just enough hairs to appear over the top. That's what i did with my Al Capone head. I made the hair denser at the hair lines and thinner in the inner areas.

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  • Admin

More suggestions... take 'em or leave 'em as necessary...


I mentioned manually animating hair before because I prefer to have full control over what is happening but using Dynamics (Force) with Hair is certainly an option as well. I'm not very well versed in that aspect so I'll have to experiment myself. If the direction the grass/weeds is primarily one direction* setting up a Dynamic Force to blow it that way is fairly trivial.


Added: Great suggestions Robert! :)


*Disregard, manipulating the direction and magnitude of the force with hair is very straightforward too.

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  • Hash Fellow

Grass gently wafted by a passing breeze....




Here's the PRJ. It plays in real time fairly well and only take a few seconds to render each frame so... it can be done! :)


waving grass02.prj


Take a careful look at the settings for the Grass in the Material and the settings and animation of the Force in the Chor.

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