Difference between GPU & render

[pingus]

Hi there !

We've got a problem with Phoenix.
Our FX man is making preview for his shoots, with GPU, but when it goes to production rendering, it has some differences.
First we don't know why, and then a problem is that the preview looks better then rendering...

here's a screen (left render, right preview ) :



Thanks !
-pingus-

[ivaylo.ivanov]

It seems you have lights in the fire section. They are not supported by the GPU preview.

[Ivaylo Katev]

the GPU preview reproduces the fire exactly, but the smoke is not the same as the software rendering, because the shadows/lighting is much more complicated than the simple fire.
in your case the reason is very simple - there is an option that represents the fire by a vray light, that option is enabled and your smoke is lit by the fire. this option is not supported by the gpu preview and this is the reason for the difference.
however, even without this the smoke will differ slightly.
btw, the GPU preview exports images with alpha channel, so if you find its result better it may be used for production rendering. there are no mate objects, this works only for simple scenes without geometry put in the fire.