Radiosity is different than most rendering solutions is that radiosity requires additional an additional processing step in addition to the normal render. This process creates a hidden meshing solution on all geometry in the scene to store what is known as a radiosity solution. Once your scene is processed, following frames during render time do not require the solution to be reprocessed. Any time a change is made however, the solution must be redone.

To use radiosity in your scene, you first need to add a photometric light. It is important to know the size of your scene and also relative brightness of the light you choose. I chose a free area light for this particular scene and placed near the top of the ceiling. Radiosity works well for indoor scenes, light tracer, a different rendering solution, tends to work better for outdoor environments. Once you have set up your lighting, its time to set up your solution.

Under Rendering > Advanced Lighting > Radiosity is where you set up the radiosity render settings. There are many options to tweak under these settings. Let’s go through them all to help better explain how to use them to better.

Initial Quality defaults to 85%, increasing this percentage will increase the light detail in your scene. I left mine at 85%. Filters are used to help smooth out those crazy looking shadows you usually get when using radiosity. My filtering is set to 3.

Meshing Parameters break down the mesh surfaces into smaller mapped out areas for light information to be received. The higher the meshing value, the less memory needed for a render. Subdividing down to 1 x 1 usually takes too much processing and most of the time not needed for a clean result.

Rendering parameters , select Render Direct Illumination. Using Re-use usually has unrealistic results. Regather Indirect Illumination can add to realism, but for the sake of time, I chose not to use this option. Filter Radius needs to be adjusted depending on the size of the room. Rays per sample controls the overall amount of rays being calculated per pixel. IMPORTANT: Keep this number as low as possible. Visit the article on Ray Tracing on to better understand this option. Once you are ready to create your solution, scroll up to the top and click start. The solution will process. Once it is finished, you should be able to see the meshing parameters created by the advanced solution.