It seems that the normal line of the surface displayed as black is reverse. With ArchiLumos1.5, only the front surface can receive light. Reverse the surface to the front.

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1. What is Radiosity ?
2. The Radiosity calculation result doesn't become brighter even though light sources are increased in the scene.
3. What is an important reminder to generate model data for Radiosity calculation ?
4. Why is it a problem, whether front or back of the surface, in Radiosity calculations ?
5. Why some surfaces were displayed as black after Radiosity calculation ?
6. When is the completion point of Radiosity calculation ?
7. How to deal with the texture-mapping or the bump-mapping in Radiosity calculations.
8. What is the relation between Radiosity and Ray Tracing when using them together ?