Afterburn shadows not showing when rendering to texture

[Robert Sundin]

Thanks for the answer Kresimir!

I´ll try to find some other way around it.
What I'm trying to achieve is to get a picture of a "slice" of an Afterburn puff that changes over time. The idea was that the dark shadow would outline the puffs shape on several white planes that intersects the AB puff at different positions. I would then render to texture those planes and then use the textures as opacity maps on the planes. Sort of a "fake" Afterburn effect. Does this make any sense?

Maybe it´s possible to achive this in some other way.

Thanks for your help

Regards

Robert