Messed up Blender models when exporting to Unity3D

Question

I have modeled a simple pocket watch in Blender. Every time I import it into Unity3D, regardless of whether I export it from Blender as an FBX or 3ds file, it always comes out missing faces! Why is this happening? I have never had problems importing models into Unity3D like this before.

Blender Screenshot

Unity Screenshots

It seems to me that different faces appear when I rotate it differently. How can I prevent this? Thanks!

Answer 1

This looks like you have flipped normals.

Blender draws double-sided by default, but you can enable Backface Culling in the Display panel (one of the panels right hand side of the view-port).

You can also enable drawing normals which draws a line in the direction each face points.

So you can use either of these draw options to check which way your normals are flipped.

This could be...

• Normals flipped the wrong way in Blender, you can select all in editmode and run 'Mesh -> Faces -> Recalculate Normals' (CTRLN). OR if they are all the wrong way around: you can simply flip the normals. 'Mesh -> Faces -> Flip Normals')
• Negative scale on the object. Blender detects negative scaled objects and shows the faces pointing the right way, but many game engines will show normals flipped if you have a negative scaled object.