displacement, gamma and render times

[thablanch]

My question is why the gamma setup would influence rendertime.

We are doing lots of vehicle, with tires, with displacement.

The production (last year) was in gamma 1.0, and a specific vehicle would take 0h;35m;25s to render (all times based on the same slave machine)
This year, the same vehicle, the production switched in gamma 2.2, the vehicle would take 5h;53m;31s ( the setup is the same,sampling, same studio, same render size, etc...)
Take this year vehicle, turn off displacement, takes 0h;27m;37s
Tried to render this year vehicle with last year setup, to ensure it was gamma related and not something else (gamma 1), with displacement on, render in 0h;34m;10s, so kind of the same thing than last year.

That is roughly 10x longer render times, for the same result.

I'm talking here about 1 vehicle, but this does apply on all vehicle we are doing, just did my tests on one to have render times.


Tried importing the gamma bitmap in gamma 1.0 and gamma 2.2, and there is 2 second difference in render time.

The result looks great however, just as it looked before. No noticeable change in quality..

So, what I'm I missing in the LWF process with displacement maps that could have that impact.

Thanks,

[Macker]

I'll wait for someone else to come in with an answer but my suspicion would be that the render engine is essentially "seeing" more now that it's calculating/sampling based on gamma 2.2 values. Noise will be more perceptible in areas where there was very little in the way of contrast between pixels because they would have appeared so dark (to the render engine).

[thablanch]

The same problem does not appear with 3d displacement. However, I need the 2d displacement to achieve the required quality..