3DS Max extrude breaks shadows in Unity

Hello!
I tried 3DS Max 2011 and 2017 and I have a problem extruding windows for a apartment building model. The extrude works well but when I import the model into Unity game engine the model shadows have little holes lines because of the extruding. Please help !

 

@colony3z Click on the mesh and enable double sided shadows in the Mesh Renderer.

If that doesn't work then your verts aren't welded.

 

Thanks man you saved my day !

 

On the shadow casting light there's also an option that helps with this, possibly called something to do with normals? Probably a more efficient fix (though I haven't tested that theory) than doing double sided checks, with the catch that it applies to everything for that light.

 

I bet if you just added a quad for each floor of the building with the surface normal up, it wouldn't show like that... instead of using double sided rendering (which can be expensive unless you're using Unity for rendering).

 

The sliders on the ight are called "bias" and "normal bias". I recently suggested playing with those values to someone to fix something that looked exactly the same as in the screenshot of the OP. It worked .

 

Ah you talking about the Bias and Normal Bias? I completely forgot about that, I don't normally face this issue to often, I just remembered double sided shadows worked when I faced them issues, but you're correct changing the Bias and such should help, but it may effect other others that don't have this issue by making their shadows awkward looking.

I've messed with the Bias before and remember it making shadows behave strange, such as a light directly behind something, adjusting the bias made the Shadow never exist lol. (Of course it was an extreme adjustment), but yeah.

Now that's not to say it's any faster or slower than any other way, it's just from my experience.