Fur: use splines for hairs

[sharktacos]

What does the "use splines for hairs" checkbox do in Vray fur exactly. I do not see it mentioned in the documentation. Could we get some info on how it is intended to be implemented? Does this mean that we can use splines to guide the fur's direction similar to xGen?

[emil.kirichev]

Hmm, this particular option kind of was forgotten (experimental) there and will be removed very soon by me -- it will be replaced with a similar one though, but much faster (the same that is available for maya hair, via vray attributes).

The main idea would be: create your fur with as little knots per strand as possible (just enough to get desired shape of strands), than checking on this option will make a spline through those knots and will dynamically create sub-segments (tesselate) each strand on render time, based on distance to camera, so you get optimal smoothness in your hair strands (the exact amount of sub-segments that are required for it to look smooth). Also able to actually remove knots for far away hairs that don't need great detail.

Will update this in the coming days, thanks for noticing.

Let me know if you have any more questions.

[sharktacos]

Okay, so it is basically a way to get detail up close for the fur (a smooth spline rather than segments), while not needing to have that detail further away, rather than a way of using Maya curves to drive the fur. Is that correct?

[emil.kirichev]

That's correct. Nothing to do with guiding the fur along maya curves. It just auto-smooths the close hairs (by using splines to do so, hence the name--but I'll change that too to avoid confusion).

[sharktacos]

Thanks that's quite helpful. I did a little test with the new curl function (also not in the docs btw) together with "use splines for hairs" I can see that it successfully renders the hairs as smooth splines, rather than as flat segments between the knots. Yay! However, it seems that the shading gets broken and rather than rendering the fur out as a tubes with spec highlights, it instead renders out as flat color with no change to the diffuse or spec. This happens irrespective of whether curl is on or not, and thus seems to be happening when "use splines for hairs" is enabled. I am using Vray 2.45. Is there something I should be doing differently?

[emil.kirichev]

No, you're doing it right, just as I said this is an old option that's wasn't entirely implemented (and tested) and will be removed. We have better spline tesselation now and I'll write here when gets added to vray fur so you can test it. So I don't advise using this option at its currents state.