Compositing Fire and Smoke

In this tutorial we will go over splitting the Phoenix FD Fire and Smoke elements in order to use them in compositing.

As Phoenix FD has no dedicated Render Elements for Fire and Smoke, we will generate these with some composting magic in NUKE.

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We will need to use V-Ray's Atmosphere and Self-Illumination Render Elements so we will add these in the Render Elements tab.

Note that you need to set the Simulator's Render Mode to Volumetric in order to get the VRayAtmosphere render element.

After rendering the image we will save it as a multichannel EXR so it will be easier to manage.

The Atmosphere Render Element will give you the Smoke + the illumination produced by the fire.

The Self-Illumination Render Element returns the fire only.

We import the image in NUKE. Each element is shuffled out and we get the following result.

Atmoshpere Pass

Self-Illumination Pass

You can directly modify the fire using the Self-Illumination pass.

To isolate the smoke, create a Merge node and connect input A to the Atmosphere pass and input B to the Self-Illumination pass.

Set the operation to Minus and the Self-Illumination pass will be subtracted thus leaving us with the illuminated smoke only.

You can now Color Correct both the fire and the smoke separately for more creative control.

Add a Hue Shift node to both passes and change the Hue rotation to 180 which will give a blue tint to the pass.

To lower the Fire Intensity, you can add a Grade node in the Self-Illumination chain and reduce the Gain by 0.5.

You can then Merge the fire back over the smoke using a Plus operation to get the final result.

Here is the final image: