How to make Arnold hair read hair growth along a spline or vertex map in C4D

[seansCWRT6]

I have an object that hair grows along using a spline placed in the length attribute of the hair material in C4D. It works in standard renderer but Arnold renderer doesn't read the hair growth animation. I have also tried an animated vertex map but again Arnold doesn't read it.

[peter.horvath6V6K3]

Can you send me a scene I can reproduce the issue with? It seems to work fine in my tests, but I'm not sure I setup the hair properly.

[seansCWRT6]

Hi Peter, thanks for replying. I have attached a test scene with both spline growth and vertex map growth included. Standard C4D renderer shows the growth but Arnold (in IPR) doesn't read it. Any help would be appreciated. Thanks, SeanHAIR_GROWTH_TESTING.c4d.zip

[peter.horvath6V6K3]

Thanks, I can reproduce the issue with your scene. I'll take a look tomorrow, I'm not sure yet what's the problem or how difficult will be to fix it.

[seansCWRT6]

Thanks Peter. Can't see why it wouldn't work. Only thing i can think of is that its maybe trying to read a C4D material (hair). But i imagine there's a way to make it work.

[peter.horvath6V6K3]

Sorry for the late reply. After consulting with MAXON support it seems that it's a limitation of the current approach I'm using in the plugin to generate and translate the hair curves. The advantage of the current approach is that it works in both, IPR and final render. There's a workaround or different approach which produce a one-to-one match with the C4D Hair in all cases, but has the disadvantage of working only in final render, but not in IPR. So I'm still trying to figure out the best solution.

[peter.horvath6V6K3]

I've got a fix which now works in the final render (Render to Picture Viewer). Unfortunately, because of the limitation of the API, it won't work in the IPR.

If you would like to test the fix before the release and you have an Arnold maintenance contract, please contact support.