What is the method for combining a fireball explosion with an RBD destruction simulation, e.g. a plane crashing in to the ground and breaking apart while emitting a fireball? Is there a way to create the RBD fracture sim and a pyro fireball separately and then composite them together, or mist the be combined in one simulaition to render them together?

Are there any tutorials of this process?

The general approach for simulation is rbd first, and then pyro, baked rbd will affect pyro as colliders.
Then render rbd and pyro separately.

Thanks for your reply. Regarding compositing the separate renders, how would you do this so that the RBD masks out the fireball, e.g. when a fractured pieces flies in front of the fireball? Someone mentioned rendering the RBD with a black material so this can be used as a matte mask in compositing, but I think I have seen an option in Mantra to use the RBD as a matte object in the render of the fireball, too?

Mine is just like you mentioned at the end, render rbd as matte for fireball.
Another thing you should be aware of is you should use the same motionblur setting for the two layers.
For rendering the rbd with a black material, I've never tried, it could be an option but need to be tested.

Thanks for you reply. So, did you select the rbd for the Forced Matte field in the Mantra Objects tab to render the fireball as a separate render using the rbd to occlude where it is in front of the fireball?

Or did you render a separate matte for the rbd and then use that in the compositing stage?

Sometimes I use the parameter "force matte", or set the parameter "matte shading" on object node.
And I also make takes for each render layers.
In this case I don't render separate matte for anything.

Thanks Benyee. I wasn't aware of the Matte Shading parameter. I'll have to play around with it.