Questions about hair rendering

[RahiSan]

Hi!

I have a few questions about hair rendering in the plugin:

Is there a way to make the hair take up less vram?
I have a model that needs to be covered in hair ( a fox) and I need about 8 million hairs because the hair needs to be so thin to look correct.
For example, does decreasing the hair segments help?
My 2 GTX 780 ti dont have enough ram to handle this amount, even with out of core textures enabled. Also, the hair renders incredibly slow.
I had it running 8 hours over night and it is still far to noisy to be usable.
I guess the material of the hair has a big impact on the render times.
I used tonysculptors hair LiveDB material on it, which parameters could have the biggest impact on render times?
Also, it seems to render fast if I just use Area light instead of a HDRI, is that correct?

Thanks a lot.

[aoktar]

I don't think hair rendering slow. But it's true geometry. So lot of hairs with intersections could caused some slow downs on specific render scenarios. You should try it different conditions and give more info. Most of features are relatively new, not older than one year. So any feedbacks help to build some database about performance, cons and pros.

[RahiSan]

Thanks for your input!

I experimented a bit and what was surprising to me was that the number of hair guides seem to have a huge impact on performance and look of the hair. It seems to be best to use as little guides as possible and let the hair material itself do the variation. I changed from 14000 guides(the default number the c4d gave me for my mesh) to about 500 and the difference in both look and render times is huge. I think also a lot less vram is needed with fewer guides.


Also, I changed from tony sculpters hair material to a more simple one I build for the fur of my mesh.

Adding a hair density map made some problems with the color of the hair. After adding the map, the hairs seemed to have the material that I had assigned used on every hair individually, instead of taking the color from the correspending uv coordinates on my mesh.

I will experiment further and see what else i can find.

[RahiSan]

Hey guys,

I have a slight problem. Using the "Density" parameter of the C4D hair material with a texture makes the color input malfunction.

Attached are two (very noisy) screenshots showing this. Is there a way to make this work or to control the hair density in other ways? Thanks.

No Density Map

With density map on face hair

[papillon]

Hey guys,

I have a slight problem. Using the "Density" parameter of the C4D hair material with a texture makes the color input malfunction.

Attached are two (very noisy) screenshots showing this. Is there a way to make this work or to control the hair density in other ways? Thanks.

no density.png

density map face.png

I experimented the same issue: a density map will scramble all fur colors. Is this a bug?

[aoktar]

Version?

[papillon]

Version?

Hello, it happens with 2.24.1-R3 and 2.24.2-TEST5
The density map is applied correctly, i.e. hair are not created where rgb=0,0,0 and interpolated on greyscale values. However, the hair color isn't read correctly from the color texture anymore.

[aoktar]

Version?

Hello, it happens with 2.24.1-R3 and 2.24.2-TEST5
The density map is applied correctly, i.e. hair are not created where rgb=0,0,0 and interpolated on greyscale values. However, the hair color isn't read correctly from the color texture anymore.

I'm not sure that you mean. But geometry should be same as c4d output. How do you give materials? Use octane materials not hair material. See hair samples from octane examples. If you can't solve it drop a sample to see.

[papillon]

I've watched the rendering hair video tutorial but there it doesn't show how to use density. Couldn't find other examples either but solved it after trying several things.
I'm posting a simple project that shows how to do it, maybe it can be helpful for others.
The hair mat has to be there, otherwise one will lose all hair effects, and additionally I added a second (octane) material with color and density map attached to it. That did the trick.

To note that no density map has to be hooked into the hair mat or that will mess up all colors (which was what other users pointed out as well).

[RahiSan]

Thank you Papillion!

That is a nice workaround!

The only Problem I see is that the Hair is still there, it's just invisible.
If you use your method to hide the hair in your provided scene it says 60k hair, same as without the opacity map.
With the "Density" parameter enabled in the C4d hair material though, it only says 25 k hair. But this, again, messes up the color.
This might have some performance or memory impact on larger scenes.

Maybe this can be fixed in future releases?