Interesting topic - how does a shader change render time?

I just got back from a 23-hour day so I'm a little loopy and I need to go to bed.

But I'll say this about that :)

If you're going to use AO, it's because you want quality. I did some quite extensive testing, which I posted in another thread (not handy at the moment.) I found that 7 samples gets you 97% (my guestimate) of the maximum possible shadow quality that Poser is capable of. Pushing it to 10 samples will make a detectable improvement, but only if you're looking at it very closely. The other important consideration is the Irradiance Caching value. For awesome quality (and SLOOOOW renders) use 99. For medium speed/quality use 50, but sometimes you'll get artifacts. For a really fast test, use IC=0. Total crap - but fast.

Personally, I don't do test renders of this shader with raytracing enabled at all, so it costs nothing in test renders. For final render, I go to "awesome" settings, and I go get lunch.

Typical medium renders for me are 1 to 5 minutes, while "awesome" will take 30 to 60 minutes.

As far as other nodes go, most nodes (particularly math nodes) are almost free. I remember posting extensive test results on many nodes - again I can't remember where.

Lighting nodes are pretty cheap - Diffuse, Glossy, Specular, etc.

The nodes that cost a lot are raytracing nodes - Fresnel, Reflect, Refract, AO.

The nodes that cost medium to a lot are the noise nodes - Fractal_Sum, fBm, Noise, Spots, Turbulence, etc.

A "mildly complicated" shader of 100 math nodes is almost free. A "complicated" shader of 10 noise nodes + 100 math nodes is pretty slow. An "unbelievably complicated" shader of 5 lighting nodes + 10 noise nodes + 100 math nodes + 3 rayracing nodes is very slow - and that would be AMUCFS.

The VSS demo skin shader has no reflect or refract, just AO, a single noisy node (spots), and the rest are lighting and math. It is only mildly slower at test rendering than your average piece-of-crap DAZ shader. LOL

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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)