Setting up the global illumination of a plant

A plant, like any object rendered by NDunes, has a global illumination applied to it to take into consideration the relighting from other scene elements that'll interact with the plant's shading. Unlike what's being done for a geometry (see Adding global illumination), we can't afford to compute global illumination caches for plants as there are millions of instances scattered in scenes and because each plant has subtle variations that make it unique compared to others.

Therefore, we use a much simpler GI setup which is calculated in real-time. The scattering conditions of a plant will determine its global illumination and we have one single option that can control the effect of the plant's global illumination. This is illustrated in the image below:

If we setup a simple biome using that plant, we can see how the GI multiplier setting will interact with the overall result we get: we can darken our image or make it look bright. The GI will tend to be stronger in dense leaves areas:

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Default GI on the left, multiplier set to x3 on the right