Fireflies attack Godzilla!

I have been working on a tribute animation to Godzilla. I finished modeling him and started moving to the rendering side. I created a cone with Displacement and attached an Emission shader into it’s Volume node to create the atomic breath. It looks fine, but when I add it to the scene with Godzilla a crazy amount of “fireflies” occur. I am using all default settings except my Samples are set to 200 for preview and render. Take a look at the renders.

WTH is going on?

I think it’s because of how there’s not yet a lot of real sampling optimizations for volumetric emitters.

You might need to use traditional surface emitters that are invisible or lamps at the time being.

Sampling light from volumes is pretty inefficient. Essentially, what Cycles has to do is scatter a light ray off Godzilla’s chest and hope it crashes into the breath next. As you might guess, that doesn’t work a lot of the time, and the brightness a ray comes back with various a lot depending on whether it hit the breath. That’s where you get the noise.

To get around it, you can add a separate dummy light to illuminate the chest. On the breath object, go over the ray visibility tab and uncheck “diffuse”. This will prevent it from casting light onto things. You can then add a mesh light to shine on Godzilla. To avoid this dummy light being visible, go to its ray visibility tab and uncheck everything but “diffuse”. That way, you use the sexy but difficult to sample volume light when things are directly visible or in reflections, but switch to an easy but crappy looking meshlight when sampling illumination.

Make sense?

I think I got it. Someone told be to try setting the Clamp up band that worked great. Just setting both Clamp values to 1.0 did the trick!

Be aware that Clamp will dull your lighting in general, and can mess with the overall contrast of the render result. Plan to light and composite accordingly.