Okay, well, I just happen to have that scene already set up, and I don’t think I did any of that stuff shader-wise with it. Though it’s been a very long time since I used this scene.
Anyway, this render took about 8 minutes. It needs a lot of work, but should suffice for the points I want to make.
First, don’t use global illumination or any of that fancy stuff. You don’t need it. This scene has a total of 4 lights, plus a sunlight, though I didn’t turn on the ceiling lights like you did. They all are set to cast 100% shadows, and there is no ambient light in the scene. But all the lights have soft shadows applied, which is very important.
The sunlight is set to stream in thru the windows, and there is a tree outside with translucent leaves that the light streams thru to give the interesting light pattern on the floor, which helps sell the feeling of realistic lighting. Since the sunlight is coming thru windows with transparency, you need to crank their intensity way up or you won’t get any light coming thru.
Also notice that the windows are not 100% transparent, they are partially reflective. Totally transparent windows don’t look right, they look like there’s no glass there at all. So I made them overly reflective to, again, sell the feeling. Also, it keeps your eyes from wandering outside and being distracted, and keeps the focus inside the room.
Two of the lights are very light blue distant lights with soft shadows, set to simulate the blue skylight coming in the windows from all directions. Since the windows curve in this scene I had to use two distant lights. Again, you have to crank up their intensities.
The third light is a wide angle spotlight on the floor near the window, pointing up at about a 45 degree angle to simulate the light bouncing off the floor from the sunlight coming in. Very soft shadows and a 90 degree half angle to light up the room, and a light brown color.
And the last light is a spot parented to the camera to simulate the light bouncing off the wall behind the camera and lighting up the room. You can see the glare from that light on the window right in front of the camera, which serves as a bright focal point for the image. Though you might want to tweak that off.
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