Blocking Shadows

How do you make it so that shadows don't pass through floors and so on. I know that a tutorial does exist as I have read one before... But I have tried but had no luck in finding it.

An answer or a link to a good tutorial will be fine.

certain entities have a flag that disables shadows, also, you should have alook at this:

http://www.valve-erc.com/srcsdk/Levels/counter-strike_source_maps.html

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Point entity to stop player shadows from being applied to a particular set of brush faces. Sometimes needed when player shadows get cast on ceilings when players walk above. Open the entity properties, click the Pick? button, and then click to add a face to prevent that surface from getting shadows. Hold down CTRL to for additional faces, then click the Pick? button again when you're done.

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