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Hair revisited

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Do you mean without the additional coloring of the hair, or just the scene without lights/cam/mantra?

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Do you mean without the additional coloring of the hair, or just the scene without lights/cam/mantra?

22855[/snapback]

I mean without the additional coloring, but with the cam and the lights...

Thanks

Arno

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Here ya go spice.

22867[/snapback]

All right, thanks a lot .....

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Hi,

since my shader is quite a complicated thing, I want to give you some additional hints about the usage...

The shader consists of four components:

R,TT,TRT,diffuse,ambient,

where R means a direct (white) surface reflection (first highlight), TT the forward transimission (especially importantant if lit from back) and TRT a strong secondary highlight. These three modes are strongly realted to the model of Marschner et al.

The diffuse and ambient components are similar to the usual Kajiya&Kay model and ar NOT physically correct.

The total outgoing intensity is calculated as follows:

Out=Light*scale_total*(scale_R*R + scale_TT*TT + scale_TRT*TRT + scale_diffuse * diffuse + scale_ambient*ambient)

With the scale parameters each component can be scaled individually. Note, that for physically based hair both diffuse and ambient components should not contribute too much intensity.

The most important parameters for changing the hair color are the absorption coefficients. They give you the right colors for both the TRT and the TT components. The diffuse and ambient colors should be set according to this absorption (see the tutorial).

allklein8ba.th.jpg

Beside the color one might want to have more (less) radiant hair. This can be done by changing the scale of the highlights (scale_R,TT,TRT) and their widths (width_R,TT,TRT; the bigger the numbers the smaller the width !!!).

For realistically looking hair/fur one needs furthermore variation of the shading parameters. To get more "texture" try to vary:

-index of refraction (slightly !!!)

-absorption coefficients

-the diffuse/ambient colors

nicebrown0pa.th.png

Cheers!

Arno

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Hi there, I'm trying to implement the paper myself in RSL, but I'm a bit confused by the way this stuff is presented.

Am I supposed to integrate over h? If not, what is the meaning of the deriviatives with respect to h all over the place in the formulae?

If I am supposed to integrate over h, surely this is incredibly slow? How many samples do you use to get a good result?

Or am I just missing the point completely?

Most grateful for any help at all :)

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Seems to me that Arno's hair shader works only when it's otl is embeded in the HIP ?

Can somebody clarify that ?

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:D

Yes....

[edit]

Please reload the attachment, since there was still a bug due to the limited numerical precision of VEX.... :(

Hope this is the final release !!!

[edit]

Hello,

is it possible this doesn"t work with Houdini 8.1.670 ?

(get error message about VEX code...)

Unable to get VEX code from:

opdef:/Shop/arno_hair_far_field

Standard Houdini Hair shader does work, but I like your shader...

thanks,

bernard

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I have one question about fur colors:

lets say that our fur base color is derived from texture map

what options do we have for controling tip color in a more complex manner?

tips are stranded from root in numerous directions so it is not posible to control them through uvs/textures becasuse they overlapp from one region to another when we comb the hair!

Does anyone have idea how to solve this?

z

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I don't understand the problem. Your tip color is a primitive attribute isn't it? Then you do it exactly the same way as you do for the root color.

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I have one question about fur colors:

lets say that our fur base color is derived from texture map

what options do we have for controling tip color in a more complex manner?

tips are stranded from root in numerous directions so it is not posible to control them through uvs/textures becasuse they overlapp from one region to another when we comb the hair!

Does anyone have idea how to solve this?

z

From the top of the head - you could group the tip points of your hair and apply the necessary colors to those, say, from a different texture.

43

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hi

I got some pointers at mailing list for this

I need to check more on this , I am reading sigraph paper about stuart little fur

will see where it brings me

thanx

Zoran

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Hello,

is it possible this doesn"t work with Houdini 8.1.670 ?

(get error message about VEX code...)

Unable to get VEX code from:

opdef:/Shop/arno_hair_far_field

Standard Houdini Hair shader does work, but I like your shader...

thanks,

bernard

So then.... if I find the time there will be a new shader...

-Arno

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so after hunting around and looking for a shader to implement in rsl I decided to take some time and actually write one so here are the results... The hair is generated as a dso and its all done in maya and MTOR... the code is inspired by the muhair shader and the results I am really happy with, here is my attempt at a hair shader...

http://www.serrao3d.com/TestMovs/hairPassD.jpg

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hey

i'm getting strange artifacts in my renders from both the scenes i d/loaded from this thread(Juice_furball.hipnc and no_colors_furball.hipnc).

no settings are changed, anyone else getting this, any ideas?

i'm using houdini 8.2.13

thx

jason

post-1653-1179220249_thumb.jpg

post-1653-1179220280_thumb.jpg

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hey

i'm getting strange artifacts in my renders from both the scenes i d/loaded from this thread(Juice_furball.hipnc and no_colors_furball.hipnc).

no settings are changed, anyone else getting this, any ideas?

i'm using houdini 8.2.13

thx

jason

Hi, this might not be it, but have you tried increasing shading rate for the hair renders to see if that helped?

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I remember Jim mentioning something about lights when he had a similar problem. I can't find the thread though, I think it was on SESI's forum.

Perhaps move your lights further away from the object and see if it helps?

M

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I remember Jim mentioning something about lights when he had a similar problem. I can't find the thread though, I think it was on SESI's forum.

Perhaps move your lights further away from the object and see if it helps?

M

thx i found the link, seems to work better, lets see how my render turns out!

BTW, anyone have any tips for white fur?

and for fun, here's a test i did with dynamics and proto fur, used the houdini VEX hair shader

http://www.divshare.com/download/655195-3d0

thx

jason

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thx i found the link, seems to work better, lets see how my render turns out!

BTW, anyone have any tips for white fur?

and for fun, here's a test i did with dynamics and proto fur, used the houdini VEX hair shader

http://www.divshare.com/download/655195-3d0

thx

jason

Hello Jason,

would it be possible to post a hip file of this dynamics+ proto fur scene?

I like to know how to combine the two.(dynamics/fur)

thanks in advance,

bern

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sure thing

it's basically a modified version of Wolfwood's furball example scene from the sideFX forums

forum link:

http://www.sidefx.com/index.php?option=com...opic&t=6069

i fed the guides through the wire dynamics, then saved it out as guides, at obj level i used the fur otl for rendering.

excuse the messy scene:)

jason

furball_4.rar

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