hi guys, i'm having trouble on rendering my pyro sim, my problem is that my pyro has no alpha and when i comp my render with a background it result invisible, any idea on how to solve it?

Is your pyro only fire? There won't be any alpha if that's the case. You can comp it in 'add' mode, or create your alpha in comp from the color data, or add smoke.

Tanto is right.
In the Pyro material, density volume renders into color and alpha.
Pyro contribution is emitting and it does not generate an alpha by design.

Yes to comp to convert pyro color to alpha and use that.

to answer tanto, i have smoke and fire, the smoke part works great and i have no problem with that, the problem in only on fire, i have already tried to add in comp, the final result is slightly better but still very far from his orginal form when is in a black background.
with color data u suggest to make an object id and from that to create an alpha? sorry for late answer and really thanks for the help, if it can help i can post some images to make it more clear