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I am making my first Loft for TS2017, It is a tunnel loft, and although I have modelled my tunnel section with textures only on the inside it appears in game with external textures too. Does anyone know why this would happen? I use 3D Crafter.

Faces can be two-sided at times. That means the software creates two faces from the same four (or three) vertices, each facing another side.

The good news is that you should not let it rob your sleep. The game should be quick in realising it needs not draw the outside and the extra data for the useless faces is not exactly much.

If you still want to fix this, I am not of much help as I know nothing about Crafter. In Blender I would say "show Face Normals" then click on the faces concerned and try hard to delete just one and not the other. Since they stick back-to-back on each other, the only rescue comes from a feature "Limit selection to visible". That means that when you click somewhere or circle some area, you only select those faces that are oriented towards you and not their twin that looks the other way. In the context of the tunnel, you want to delete the outside half of the skin. So when you look at it from the side, you look at what you want to delete.

There are no duplicate faces I'm sure, it was made from a primitive cylinder shape, I textured the shape on the outside initially, then made it double sided and deleted the outside faces just leaving the inside ones.
I don't suppose it's anything to be concerned about as you say Andi, I just like to try and find out where I went wrong.

If you are so sure, then it make another vague memory of mine more plausible: There were some faces in my life long ago, that happened to be two-sided without any doing by me. That war really long ago and to this day I am not sure whether
a) the plane in question was two-faced in Blender and I did not realise,
b) the material is double-sided (*)
c) it was a default assumption inside Rail Simulator (sic).

(*) I also vaguely remember a check box somewhere for "two-sided material" but that will have been for 3DS Max, in one of Derek's blog posts.

However, in the years gone by, I read so much about all faces needing materials or else the export or loading crashes, that I count my faces carefully. Maybe I should relax on that front. But I am sure I had such nonsense once - a double-sided plane that was textured on one face but not on the other. Nice one if that stop your model from loading. But that has no bearing on your situation since you already delete the outside faces.

Long live the second side of the inside faces as long as you get it for free!

I was just looking at the developer notes earlier, there is a first time for everything, and it says that non-fx shaders produce double sided textures automatically, but I used LoftTexDiff.fx for this.

In 3D Studio you can set materials to be single or double sided - perhaps there might be something similar in Crafter ?

Cheers
Paul

Maybe there is Paul, it's very hard to find information on Crafter I have found. There is a tool to make faces double sided, you would think that unless you had used that tool you would have a single sided face.

Briyeo, I think you are thinking of a tool that doubles up polygons? In 3ds max it's known as the 'Shell' modifier. Doubling geometry is one way of doing two-sided faces, but there's also materials that render a single polygon on both sides. Default behaviour for max at least is not to make double-sided geometry unless you specifically ask for it; I'd expect 3DC to do the same.

Yes Crafter does the same, my model of the tunnel loft section only has faces on the inside, but the loft when in game has faces inside and outside . As shown in my screenshots above.

If you're 100% sure that the model is correct, it must be the materials rendering double-sided methinks. Unfortunately, I dont have crafter, so I don't really know how materials work in it