Intense emission without color change? (cycles)

In a model with engines, I wanted a strong red glow inside the engines, leaking out … but if I use emission with enough strength to let it bleed enough, it changes color … i wanted it red … it goes pink, then white. How do you do strong emissions on faces, that don’t change colors?

"leaking out’ sounds like volumetrics so - not in cycles.

It sounds like you might want a larger, shaped, object to get this effect, with a lower intensity, rather than a point or small mesh light source with a very high intensity. The shape of your engine would determine what you use.

Maybe you can leverage the Color Ramp technique shown in thisBlendSwap Area Lamp.

It’s a very good question! I also wanted to know the answer, the blendswap file linked by Atom has the key.

The Light Falloff node can be used to slow down the discoloration:

Light Falloff:


Original for comparison:


All that comes to mind:


When you see that effect in a movie, it is done 100% of the time with compositing. The light is not turning white, it’s blowing out the exposure of the camera. Turn down the exposure in the color management panel and you’ll see the red come back with the increased energy, but you’re likely still going to want the artistic edge that compositing allows.

Complex question.

A color remains at the precise chromaticity values, no matter how intense. A red of primary xy coordinate will remain the exact same red at values 0.01, 0.1, 1.0, 100.0, 1000000.0.

To elucidate the phenomenon you are seeing, there are two terms worth familiarizing with: Scene Referred and Display Referred.

When you are using a Scene Referred model, 1.0 has no special meaning. Display Referred models (also known as Output Referred) place special meaning on the maximum values (often 1.0), as they are the maximum data value you can feed to a format or a display. When all channels are maximum, the maximum output is reached, which in most instances is achromatic (or it should be in an ideal device).

So what happens between a Scene Referred model and a Display Referred model? A transform has to take place.

What you are seeing is your intense red from the internal Scene Referred model being transformed (through color management) into your Display Referred output. This means that the red has some other values mixed with it, and as it approaches the Display Reffered maximum values, all the value ‘converge’ as there is no more room on the red channel to increase intensity[1].

You will see something unique happen if you choose a fully saturated isolated channel and increase the intensity.

The correct method to controlling the transform is to control the tone response / transfer curve of the Scene Referred model to the Display Referred model. The curves adjustment at the sidebar with exposure can accomplish this IIRC. You can also generate your own unique tone response / transfer curves, create an OCIO entry for them, and reuse them if desired.

I’d heavily recommend everyone reading this thread to go and read Jeremy Selan’s PDF at http://cinematiccolor.com. Mr. Selan has won his second Academy Award recognition for his work on OCIO; the color system Blender uses. The document does a wonderful job of introducing people to the concept of color, and highlights key differences between Scene Referred and Display Referred values. The document was adopted by the Visual Efffects Society as a reference starting point.

Hope this helps…
TJS