Slow Sleasel

Render times have not been our friend this semester, especially in the lab. Jennifers Sleasel has been particularly hit hard by this. I did some test to try and figure out what was slowing it down. Here is the original render, which took 1 min 9 sec (Mental Ray preview quality @ 640x360, on my laptop):

I tried to render it with a single ramp shader on all objects. Did render quite a bit faster: 14 seconds!

Even when I made the material reflective it only took 22 seconds:

But of course this was not the look Jen was going for. But is renders way faster so the fact that the original scene has a gezillion shading groups or many empty UV sets was not bogging down the render. Tried to render the entire scene without any raytracing:

Now that rendered in 17 seconds! But then again, it also has no shadows. I turned raytracing back on but disabled the shadows, which are obviously all set to ray traced or they would have shown up in the non-ray traced image. This took 33 seconds:

But we want shadows. What if we kill the transparency on the glasses? Rendered in 38 seconds, so that is one of the most important factors in slowing the render down:

The image looses a lot of visual quality. Digging through the scene I did find one other thing. The counter (Wood Red) had a reflectivity of 0.002, and one of the ramp shaders feeding into it had a reflectivity of .1. So full reflection had to be calculated for it though it hardly showed up. I found a few more reflective ramps and killed the reflectivity on the ceiling:

Render time: 1min01seconds. So that is 61 seconds versus 69 seconds for the original, a more than 10 percent gain. May not sound like much, but considering that the entire animation is 150 frames, this will shave of 150 times 8 = 1200 seconds or 20 minutes of off an almost three hour render.

I also tried rendering it using Maya Software. To get the smooth Sleasel one has to create a proxy. Still it renders really fast. And with a lot of aliasing artifacts at preview quality. Needs to be close to production quality to get the wood pattern to look nice again, and by then it renders at least as slow.