- Feb 13, 2019
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This may not be affecting your render times, but maybe it could be a factor. Most renders do not need to have light path lengths set to infinite. In Render Settings >> Optimization >> Max Path Length the default setting is -1 and that will contine to calculate the paths until DAZ thinks there is no more light to bounce. In most cases setting this value to a positive number will only allow the path to be calculated a finite length. I am supposing that when you use ghost lights that there are just too many paths to calculate and that is why your render may be taking so much longer.Well, this one took me six hours. I'm using a 3090, rendered in 2K at 99% convergence. I had three spots on the model, a fourth spotlight coming through the window, and a large overhead ghost light. Bloom filter on, max path length -1. Several reflective surfaces and the space behind the model is walled in with everything retextured from the way the asset came. I'd love to have someone tell me that it shouldn't have taken six hours, but I wasn't able to get a better result with different settings. View attachment 2922776
In the render you posted, there are only a few reflective surfaces and with matte or flat surfaces light falloff is so significant you could likely get away setting the max path to 8 or even less. That could exponentially lower the render times.
Also note, that DAZ calculates these light paths for the entire scene not just the visible portion. That is a lot of calculating, and all of that is being done on your 3090.
I have used ghost lights in the past and noticed a similar lengthening of the render times. Now I just add more lights or lights with a wider dispersion to accomplish the same thing ghost lights do. Although there are some situations where ghost lights may be the only answer.
Edit: Just to be clear, setting it to infinity does not actually mean DAZ calculates the path to inifinty. It will stop when there is no more light to bounce, in some cases this could be less than if you set it to a specific number. But most of use don't render a single asset in the void of space, so there will be paths to calculate.
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