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Radiosity is essential to creating a photorealistic render and Blender fully supports radiosity calculations as a way of adding onto the shading of an overall scene. In this example here, I'm going to run through all of the different components to radiosity and quickly show you the essentials of setting it up and using it in your render. Radiosity, as you know, refers to the way in which light when it's absorbed by something is actually emitted back out into the environment. So there is a couple of major components.
First you need to set up radiosity over here in your Scene Render sub-context in the Render panel. Make sure Radio here is enabled. The second thing then under Shading, for each of the materials of the objects in the scene, if you want them to be able to emit some of their light that they get back out into the environment, you need to set the Emit Setting down here. Notice I have this set at Emit of 0.1. Just a little bit of emission is all you need. It's a very subtle, kind of warm, soft, glow effect.
So you don't want it really bright and glaring, otherwise it's overblown. Then I just want to point out to you that the other materials now don't emit at all. So after you have set up the emissions, the next step is to click the Radiosity sub-context here and collect the meshes that you want to participate in the Radiosity calculation. It's a very compute intensive calculation and can take quite a bit of time and not everything needs to participate. So this step gives you the option of selecting the meshes that you want to participate.
I am going to go ahead and press A to select all of them, and then you just click Collect Meshes. When you do that then, Blender isolates out the meshes that you have selected and shows you kind of a window of gray -scales and white-scales where these objects are going to be emitting here and then these other grayish objects are going to be having the light that's emitted from this object cast onto them. Then really, all you need to do is click GO and Blender will whip through there and go through all of the different meshes and do what's called patches of light and kind of calculate the degree to which the shading needs to be effected for that particular patch based on the emission and how far away it is from the object.
Once you have done that, then the next thing is actually applying this to your render. The major setting here is the Multiplier effect. So now if we click Render or press F12, we see we have the full-blown effect and it's pretty bright here and this is absolutely no light. This scene is lit by this emitting base. So we can tone this down a little bit by pressing 10 here, and we do another render, the effect is a lot less.
If you want a very subtle effect, then somewhat multiply of about 5 will work. We also can do automatic on the fly gamma correction. So if we crank Gamma down to 1, now the effect is heightened based on the difference between the emitting mesh, and the other meshes that are affected. So that is Radiosity in Blender and how you can make it work in your scene to add a little bit of extra photorealism.
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