Here's what happens even if you remove an entire wall, but you don't use really high samples and bounces.

I'm using 150 samples and 4 bounces. My EnvSphere luminance value is 8x.

Observe the splotchies that start once the sky is obstructed by the room so that less than 1/4 of the environment is visible.

Also, observe the light leaks, especially along the floor-wall joint in the back corner near the armoire.

These leaks have been there forever and SM tells me they can't correct them. They are an artifact of the irradiance caching algorithm. IC gives us speed, not accuracy. In cases like this where the light source is really bright, the inaccuracy is really high.

You can turn off IC but the render times will make you choke.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)