Since fire/smoke is currently only supported in the internal renderer, what are some good workflow ideas for bringing fire and smoke into a cycles scene.

My current idea seems too labor intensive:

Rendering out the Cycles frames, then duplicating the scene, setting the renderer to internal and changing all of the materials to masking alpha. Then compositing the frames together.

Is there a better way until volumetrics are added to cycles?

  • $\begingroup$ possible duplicate of Composite transparent overlapping objects from different scenes? $\endgroup$
    – Aldrik
    Commented Sep 11, 2013 at 21:51
  • $\begingroup$ No I can composite 2 scenes no problem. The question is more about scene setup workflow. Having to have 2 sets of materials for the objects in the scene that will be rendered via cycles is a hassle. $\endgroup$ Commented Sep 11, 2013 at 23:47
  • $\begingroup$ thats simple prepare your animation in cycles with cycles material,duplicate your scene full copy,leave all cycles material on place put fire on place you need and render in BI cycles material will be ivisible and crate mask just set backround black and finaly composite both scenes $\endgroup$
    – Utas
    Commented Sep 18, 2013 at 23:25
  • $\begingroup$ I was hoping to be able to easily link everything but the materials, that way I can still make tweaks to the animation/etc without having to completely redo BI sim stuff. $\endgroup$ Commented Sep 20, 2013 at 3:29
  • $\begingroup$ BTW, blender cookie made a tutorial on this recently $\endgroup$
    – gandalf3
    Commented Oct 11, 2013 at 2:25

2 Answers 2


Expanding on tobkum's answer, an example workflow using the technique in this tutorial might be:

  1. Setup BI scene (simulation, etc.)

  2. Create a new scene for Cycles, with Link object data

  3. Create Cycles materials, linking to Object instead of Data so BI and cycles materials are not synced:

    enter image description here

  4. In the BI scene:

    1. Create BI materials, again using Object instead of Data.

    2. Disable shadows for all BI materials except the smoke

    3. Create renderlayers for smoke and smoke shadows using the Shadow pass.

    4. Create renderlayers for reflections and refractions, and remove sky by setting the Horizon color to black.

  5. Setup compositing in Cycles scene:

    1. Create renderlayers for foreground and background objects

    2. Multiply BI shadows with cycles background layer

    3. Alpha over BI smoke over cycles background layer

    4. Alpha over cycles foreground layer over composite

    5. Add or Mix BI reflections and refractions to composite

  6. Render


As of version 2.73 it is now supported and has become much easier, see my answer here:

Rendering smoke in Cycles?


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