How to simulate lighting for very small windows

Hi everyone, For windows made up of many narrow-width glass arrays, the V matrix is zero when the 3-phase method is used. The illuminance value at the specified point in the room is also zero. Is the width of the glass narrow? Is there any way to improve the accuracy so that the simulation results are not zero?

Are you certain that your windows are facing the inside? Both light and glow only emit light on one side of the surface, so you have to make sure they're facing into your space. You can invert your surfaces easily with xform like this:

xform -I window.rad > window_flipped.rad

Are you using a glow or light material on you windows? If windows are small and distant, sometimes the light material works better because it uses deterministic sampling.

What is your -ad setting? If you're using glow, increasing the -ad and decreasing the -lw can help find small windows.