Render shadows only?

[NStocks]

Is it possible to take a sketchup scene (that has multiple materials already applied) and without changing the model, render out the shadows (and tones/darker/lighter areas) that can be applied over another render in Photoshop?

[Fletch]

This would be called a "shadow pass" there is an Alpha Pass or other various render passes in the Technical render presets folder. But no Shadow Pass, sorry to disappoint. Or, also known as a "Shadow Catcher", but also this material isn't currently supported by the render engine.

The closest you can do is to render a "clay render" with the clay render setting/mode - this will turn nearly everything to be light gray but otherwise render exactly what you were seeing in the standard rendering. Then you would render a set of "Alpha" passes for each of the objects/buildings you want to erase/mask out of your Clay Rendering. Use those alpha masks to isolate only the surfaces where there are the shadows you want to use.

Some related threads:
Subject: Shadows effect with Gimp