Tips for Rendering Poser Hair
In Poser Pro 2014

Note: The following thoughts concern strand-based hair created in Poser's Hair Room, not modelled/trans-mapped hair created outside Poser. Hair Room hair is of far more interest to me, because I believe it has much more potential for realism, given the proper settings.

One of the special challenges of rendering Poser hair using IDL (Indirect Lighting) is that at this point, the program generates artifacts with the IDL–dynamic hair combination. These tips are aimed at getting the best out of Poser Pro 2014 hair renders, while understanding the tradeoffs between quality, render time, and unwanted artifacts.

I must qualify at the outset that different environments and lighting setups may yield different results, even on the same machine and installation of Poser. So for the record, the particular setup in question here contains the following:

• An enclosed room prop with one wall set to give off ambient light.
• One raytraced point light with Shadow Blur Radius set at 5.0 and Shadow samples set to 94.
• One raytraced infinite light with Shadow Blur Radius set to 5.0 and Shadow samples set to 94.

Not all my findings are documented here, but here are some things I have learned.

• If you are using a skullcap, unchecking Visible (in the Properties tab) is not the same as setting full transparency in Materials. By combining Visible with full transparency, one can provide root shadowing that you cannot get simply by making the skullcap invisible. As a result, you can use far lower hair density (in your Hair Room settings) and still cover the character's scalp. (The unfortunate side-effect, however, is that you will introduce rendering artifacts.) In the skullcap's Properties tab, check Light emitter and Visible in Raytracing, but not Casts shadows. Do not check Visible in Camera, or the technique will not work.
• The splotchy artifacts can be reduced a great deal by cranking Irradiance Caching settings, e.g. to 80 or 90. But shutting IC off (i.e. 100) doesn't work. At least in my experiment, I ended up with a hard line at the edge of the skullcap.
• Some of my testing suggested that for best results, use your character's face skin material settings and apply it to the skullcap, and then add full transparency. But that makes little theoretical sense and requires more testing for verification. It's something to try if your artifacts aren't getting blurred or reduced to the degree you would like.
• Gaussian 2 is the optimal setting for reducing splotchiness without sacrificing too much crispness in the overall render.
• Neither a ridiculously low Minimum Shading Rate, nor a ridiculously high one, will give you good luck on the artifacts front. (I tried as low as .01 and as high as 1.0.) My best results have been in the .15 to .20 range.