LuxCoreRender Light Groups
Light groups is a feature that can greatly help you composite and evaluate the lighting in your scene. It allows you to bundle one or more light sources into groups and change their intensity and color during the rendering process.
Light groups are intended to help setting up the right mix of lights, but for any final renderings it is advisable to adjust the light intensity values correctly before starting the rendering. The reason for this is that LuxCoreRender bases the importance of the various light sources on their initial brightness. If a light source is boosted a lot, this will increase the noise level in the image. Also adjustments to the light color are an approximation and setting the color right from the beginning will result in a more accurate rendering.
To use light groups you first create the new groups in the exporter and then assign the light objects (or mesh lights) to their respective groups. In the example shown below, we have a scene with lights from the sun, TV and some incandescent lamps, assigned to the groups "sun", "tv" and "spots". Assigning every light to a separate group is not required, as any light that is not assigned will be assigned automatically to the default light group.
Gain: This controls the intensity of the lights in the current light group. Note that the Gain value does not control the actual light intensities in the scene; it simply controls how much of the lights in this group contribute to the render. That is increasing the Gain value will make the already rendered samples of that light brighter, but it will not make the light reach further away from the source.
Color: This modifies the color of the light. Note that this is a multiplier.
Temperature: This modifies the color of the light based on temperature values. This is also multiplied to the original color of the light.