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I've an object in Blender. Because I want to do some UV-unwrapping using ThreeJS (see here) I determined that I need merge two of the sides to correctly unwrap.

So before exporting the .blend as a .obj object I selected the Tris to Quads face option to create a square face for the two sides as opposed to it being made up of two triangles. Here's what it looked like in Blender:

enter image description here

But when I import the .obj and .mtl file into ThreeJs I get this:

enter image description here

Is this a problem to do with me not updating the material being added to the new object? The handles appearing white makes me think this is the case. If so how can I go about fixing it?

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Katana24
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    Are you sure normals are facing the correct way? (Outwards)? I remember there is a hotkey in Blender to recalculate all normals. – Banex Jan 16 '17 at 09:55
  • I recalculated the normals in Blender and then followed the same export process. Unfortunately the result is still the same. – Katana24 Jan 16 '17 at 10:34
  • Try setting the material to `side: THREE.DoubleSide`. If that helps, your problem has to do with the normal-directions. In blender you can enable displaying of normal-directions in the right-hand menu (select "Face normals in section "Mesh Display"). The automatic fix is in edit-mode, select all (shortcut ) and then via menu "Mesh" > "Normals" > "Recalculate Outside" (shortcut +). – Martin Schuhfuß Jan 16 '17 at 10:50
  • I set the materials to THREE.DoubleSide in Blender as I installed a plugin for it a while ago. I also recalculated both the inside and outside normals. It worked actually. Thanks for that. Can you post it as an answer and I'll mark it? – Katana24 Jan 16 '17 at 11:07

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When I see something like this, the first thing I usually do is to set the material to side: THREE.DoubleSide. If that helps, the problem has to do with the normal-directions (so the face is actually there but isn't rendered because it is facing away from you).

To fix this, you should try the following:

  • In blender you can enable displaying of normal-directions in the right-hand menu (select "Face normals in section "Mesh Display").
  • You should now see if any of the normals are pointing inwards/in the wrong direction.
  • There is an automatic fix that works well for properly constructed meshes:
    • select object and switch into edit-mode (<Tab>)
    • select all vertices (shortcut &ltA>)
    • via menu "Mesh" > "Normals" > "Recalculate Outside" (shortcut <Ctrl>+<N>).
Martin Schuhfuß
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