By default, a is calculated at the current frame. If you are animating objects and you want to perform a radiosity solution at every frame, turn on Compute Advanced Lighting When Required in the Render Setup dialog Common panel Advanced Lighting group.
Once the renderer starts processing each frame of your animation, it computes the radiosity solution for each frame as required. This occurs, for example, when an object moves or a light intensity changes. If nothing changes in the scene from one frame to the next, the radiosity engine does not recalculate the solution.
The radiosity solution is calculated for each frame if any object is animated in the scene (the default is to calculate the current frame only). You specify the parameters (goals/quality) you want to reach on the Advanced Lighting panel. Before rendering the entire animation, we recommend first running a solution to verify that it’s successful. These parameters are then reprocessed for each frame.
You go to the Render Setup dialog Common Parameters rollout and enable the option Compute Advanced Lighting When Required, and then render the scene. The radiosity is processed for the first frame and then rendered. 3ds Max then moves to the next frame, processes radiosity, renders, and so on.