A small mod to fix roof shadowing. Normally, outdoor roofs are ignored by the sun shadow caster, causing the roof eaves along the outside of a building to render incorrectly. This mods corrects this behavior.
Q. Is there a performance impact?
A. No. The code behind this mod only runs for 1 tick whenever the suncasting layer data is redrawn, which only happens when something is built or removed.
The main issue is that outdoor roofs will show whether as passing through, so if you have an outdoor roofed area (eg a covered bridge), you'd see the rain fx moving through it. This is a technical limitation given how Rimworld's shadowing works. This issue does not apply to natural roofs such as the ones in caves.
Until a fix can be worked out, there are two workarounds to this. Say for example you have an outdoor covered warehouse. You could either 1.) replace the roofing with natural roofs like thin rock that caves use (using devmode cheat), or 2.) Use an invisible door mod to section off the warehouse to make it think it's indoors.