Question about importing FBX and clipping poly

Hello

I'm pretty new in the scene of modeling and just started to use blender 2.8.
I noticed when importing that you need to do a couple of additional things to actually make the import work.
My very first model (The white one), No issue at all. I could say the same about my second model (the red one). However, Now that i have finished my third model (Blue one) the poly of the model does really weird things, I think its called clipping but i'm not sure.

Why does this happen and what is the cause? Is there a way to prevent this?

All models had in advance Shaders which failed to import. Even after clicking the button export materials the materials where black / gray. , maybe that could be because Blender 2.8 is still in Beta and they changed their composition or smth? who knows.

In The reference image i used unity materials.


Thank you!

 

Your normals are flipped on the blue one.

https://www.katsbits.com/codex/flip-normals/

 

Thank you for your input! It makes total sense now!

 

It's one of the trickier things I've found when working with Blender. Sometimes it isn't always immediately apparent when working on the model.

 

Not sure what would cause your normals to invert in the first place, but a few common practices on export that will save you some trouble are :

freeze transformations (this means to zero out the x,y,and z transform values so your object will arrive in the engine centered on its pivot)

delete history (not sure how blender works, but most 3d apps keep a construction history)

triangulate before any baking (helps avoid shading issues, make sure to keep a quad version of your model in case you need to make edits later)

check your UV sets (sometimes jumping between various programs or performing certain operations can create a new UV set even if you didn't intend to. Most programs will display the first UV set but sometimes can be an issue that will screw with you if you aren't aware)

check your scale (get this set up early. Make sure you've got your apps set so that one is not outputting at 100x scale as the others. Not hard to fix but if you've got a lot of parts it can be annoying.)