Problem with the mesh(simple gate, cube object)

Hi I am new to this forum.

I hope this is in the correct place in the forum.

I am in the process of making my first model, that hopefully will work in HL2 episode 2 engine. I do not always have time to work on my project at the moment. I have purposefully attempted an overall simple cube type object, a canal bar at 256 hammer units as my first model. In blender 256 hammer units is very very large. I have completed various on-line tutorials but they can only go so far. And do not relate fully to what I am trying to accomplish

At this time I have got to the stage of UV Unwrapping. Though I have ran into a few problems that I do not believe relate to UV Unwrapping.

I have noticed some strange things happening.

In the first picture I am in solid view mode, the top bar has no holes in the object/mesh, it looks solid.

http://imageshack.us/a/img819/8028/aoproblemcanalgate3.png

But in the 2nd picture I am in texture view mode and the same top bar has holes, parts of the object seem invisible
http://imageshack.us/a/img59/1289/aoproblemcanalgate4.png

http://imageshack.us/a/img708/3202/aoproblemcanalgate2.png

Why do you think this is happening? Some parts of the top bar seem invisible when viewed at certain angles

Today I have also tried to add an ambient occlusion bake it into the a texture, so I can export that into a art program and create a texture for the gate but again I ran into a problem.

It seems because I have duplicated various parts of the gate to create a whole gate. When I bake ambient occlusion it takes the shadows of the duplicated objects and casts shadows on objects that should not cast shadows as they share the same UV Space.

http://imageshack.us/a/img545/9426/aoproblemcanalgate.png

Is this because they share the same UV space? I really don’t know why this is happening. Does lighting matter when trying to bake ambient occlusion into the texture? Mine just does not look correct for some reason

Can anyone help I am a beginner with these matters I would really appreciate that.

Thanks kind regards

For invisible faces, the face normal may be pointing the wrong way. Turn on normal display in the Properties panel (N) under Display while in edit mode. You can flip selected faces with W / Flip normals. You can auto recalculate face normals by selecting them and Ctrl+N, though looking at how you’ve may your mesh you’ve made it difficult to get a good recalculation so you may have to manually flip faces.

Does lighting matter when trying to bake ambient occlusion into the texture?
No. You can still bake AO with no lighting in your scene

Thanks Richard Marklew,

Yes, I went to Mesh display and turned on the normals, they appeared as lines. The mesh that was causing this invisible problem had the normals inverted. The normals lines were pointing to inside the mesh where as all the other mesh normals were pointing to outside. I Recalculated and flipped directions of the normals this solved the problem. The object appears in texture view mode correctly.

Thank you.

I was told to bake the ambient occlusion so it works correctly that there should not be overlapping UV’s. This model is made from duplicated parts that were previously unwrapped to make the whole gate.

I think I just need to move the overlapping UV’s away, out of the bounds of my UV space. and then return the UV-islands when I export the UV’s, is this correct?

Kind regards