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Marc

Hair revisited

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1989 yowzers glad we using the latest tech, combine this with phong from 1973 and we are smoking!!

j

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I've made an implementation of Marschner shading model for hair and would like to share it with community.

post-4029-129347231516_thumb.jpg

See here:

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I would like to return to the guides issue and ask how I could stick the guides on the geometry skin after the guides are copied/created?

I am asking this because I would like to use my custom guides to deform the current guides but I didn't figure a way to do it on a deforming skin.

Thanks.

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the custom guides thing is really wanted here too, for long hairs..unfortunaley the hairshader cvex stuff overwrites it...

i hope sidefx implements sth for long hair styling..plus better pbr rendering.

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There is a way, but it requires a bit of hacking of the fur system. On a recent job I groomed long hair in blender and then brought it in to Houdini for rendering.

Having said that, I don't have Houdini in front of me, so I can't tell you exactly how to do it since it was about a year ago :). But it is definitely possible.

M

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There is a way, but it requires a bit of hacking of the fur system. On a recent job I groomed long hair in blender and then brought it in to Houdini for rendering.

Having said that, I don't have Houdini in front of me, so I can't tell you exactly how to do it since it was about a year ago :). But it is definitely possible.

M

did you bring in guides, or all the hair geo (polys?)

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I brought in poly curves and plugged them into the guides of the fur system. In v10 it required some hacking to get them to stick on to the skin since the curves needed to be on points, but I'm fairly sure they changed that in v11 where the curves can be independant of the base skins point count.

M

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For me the problem is not to make the guides but make them stick to the deforming/moving surface.

My idea is to make them just for the first frame and after that make them follow the surface, I couldn't figure it out how.

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Take a look at where the standard guides are inserted into the fur system. Basically all you'll have to do is replace those with yours and in theory it should all work out as far as binding it to the surface. Sorry for the vague answer, but I have no Houdini where I am right now.

Hopefully it puts you on the right track though. If not then let me know and I can try put something together on Monday when I'm back at work.

Cheers

Marc

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I am trying now to use guides generated on a low res Geo to guide the fur created on the same Geo but subdivided, but I got an error on the fur saying that the two geometries doesn't match, is there a way to make it work or I have to always use the same geometry to create the guides and the fur?

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I'm pretty sure you need to use the same geometry to create the guides and fur. What version of Houdini are you using? If it's v11 then you should have an option on the fur object to "use scattered guides". That will scatter points on your skin geometry and use those base points as the guide locations.

M

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Thanks Marc, I was after that because I saw Andy Boyd´s work (www.andyboyd3d.com) with fur and it seems the he uses the low geometry to create the guides but I don´t know how he uses it on the high res geometry. If you have any clues feel free to share.

Anyway thanks for the help.

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Hey

Well you just use the lowres geometry to generate the guides and move the hair, and then what you render is the highres skin and the hair (not rendering the lowres guide generating skin). Make sense?

M

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The problem to use the low res geometry to create the guides and fur is that even if you render the skin as high res you can see the flatness on the fur just like the low res geometry.

To avoid that you need to create the guide and fur on a smoother geometry.

Edited by Mzigaib

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Did anyone have problems to render hair in certain frames even if the only difference is the distance to the camera?

I am trying to do a turn table with my hairy character and I can render all frames but 2 of them, on those mantra crashes, I tried to reduce shadow map, reduce dicing and the result is the same.

Any ideas?

Solved:

It had to do with my animated geometry that was on the disk, when it tried to loop the animation I had a problem with the motion blur calculation which somehow made mantra crash every time.

Edited by Mzigaib

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below link is to the disney paper regarding their changes made to the MARSCHNER shader model.

the results are impressive. most of this is over my head, but i hope someone with the knowhow can implement the disney alterations.

'tangled' has some simply amazing hair throughout, and this paper shows how to implement changes that result in the production shader they used on 'tangled'.

a sweet side effect is a 3 fold reduction in render time. :blink: additionally, the shader works under a number lighting conditions.

42MB

Direct from Disney link

mirror

mediafire link

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