Quote - Yeah, DM shadows are good to have in the arsenal. I suspect bb is right on the bug call - I've tinkered all afternoon on this and just can't shift that "necklace" effect.

bb - curious about the fact that you had the same issue with RT shadows in Poser Pro. Is that for real?

I don't get a necklace - light leaking into deep shadow - in that RT render I posted. However, we see some strangeness on the hip/thigh area. I'm not sure that effect is fully qualified as a "bug". I think that case has more to do with numerical accuracy with regard to the angle of incidence.

For diffuse reflection the AOI is the only driver, and reflected luminance is entirely based on the cosine of the AOI. The slope of the cosine function near 90 degrees AOI is at its maximum there. The result is the luminance changes most rapidly exactly at  the terminator.

Now it just so happens that there is a disagreement about luminance between GC(2.2) and sRGB. The slope of luminance changes are different at the very low end. Thusly, you would get a more pronounced rapid rise in near-terminator luminance from GC than is realistic. There has been some discussion of this phenomenon, and frankly I'm convinced that GC(2.2) is naive and should not actually be used if you're dealing with these marginal luminance situations. Coupled with the rapid increase of diffuse reflection near the terminator, we get a rather obvious departure from realism.

To fix it, we'd have to switch to using sRGB conversion instead of GC(2.2). GC is strictly a power function, whereas sRGB is part linear, part power, and has to be fitted together with quite a few more nodes. It's worth it when you get into these large, barely lit areas. Poser PRO should have implemented sRGB as an option, instead of just GC. With shader-based conversion, sRGB is possible, but way to esoteric for most people. Heck, there are still thousands of users who insist I'm full of crap on this topic and they don't need to use GC.

It's very similar to a long-running debate at dpreview.com about the impact on image quality associated with the use of filters. The Pros insist that even a $300 filter is off limits as it compromises image quality. The hobbyists claim they can't tell the difference. The debate is endless.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)