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Unable to flip normals


George Orellana
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Hello folks. I finally decided to come here and ask probably a stupid question but I have tried googling and searched online and have not found a solution to my problem, so I am hoping someone here may be able to help.

I have a big wall that requires it to have multiple textures and some doorways with as little prims as possible. Normally with regular prims this would require a lot of prims, so I figured the best way to do this would be to use mesh to create this wall. I created my wall in blender 2.63a, used the dissolve tool to get rid of unnecessary loop cut edges, removed doubles, created my uv map and assigned different materials to each face. Everything works well as expected even being able to walk through the doors when the mesh is prim instead of convex hull. The only problem is that I have a face that no matter what I try to do is invisible, my guess is the normals are flipped, however flipping the normals has no effect when I upload it to SL it is always invisible no matter what.

 

As you can see here I assigned my materials to each face.

Screenshot from 2012-06-26 23:22:42.png

 

Screenshot from 2012-06-26 23:19:30.png

Screenshot from 2012-06-26 23:18:53.png

When uploaded to SL all faces are correct except that top corner face.

 

Screenshot from 2012-06-26 23:17:30.png

 

What am I doing wrong? Any help for this mesh noob would be greatly appreciated. I will check back in tomorrow morning as it is almost midnight here and this blender problem has given me a headache :/

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Not sure what's causing that, but here's what I would do:

  • In Blender, enable "Display face normals as lines" in Edit mode and see if the normals actually point outward.
  • Since the Dissolve tool was used to delete edge loops, make sure it left no N-gons behind, i.e. make sure there is no face in the mesh with more than four vertices. The exporter or importer may be unable to handle them properly. Triangulate the mesh before export if necessary.
  • Reload the exported .dae file back into Blender. This would reveal if the normals were flipped during export.
  • Ask a friend to look at the mesh in Blender. Maybe you are missing something.
  • If none of the above helps, file a bug report to the JIRA and attach the .dae file to it.
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How many materials do you have assigned to the faces of that mesh?  If you exceed the maximum you may get invisible parts to your upload, I believe.  Either 6 or 8 is the maximum...I forget which, but check the mesh wiki and it's listed there.

If flipping is a problem in Blender then go into edge mode and press ctl shift alt M to check for inside faces (non-manifold) and delete them.  I noticed when these exist Blender has a problem resolving normal recalcuations.

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Kudos and hugs to you both. I was able to upload my wall with all faces now. It was a mixture of both. After following Masami's suggestion to display face normals as lines it revealed that there were no faces there? I don't know how that happened, all there was was small triangles in some corners. I deleted all those and recreated my faces. I then tried to upload my mesh again and still the same problem. So then I tried to follow Nancy's suggestion and deleted the material assignment from that portion and that worked. 

 

Screenshot from 2012-06-27 08:44:51.png

The only problem I have is that the little portion under the door is not acting like it is the same texture face, I guess that I could fix that my messing with the UV map but in this case that part will be hidden by a floor so this will do just fine. 

 

Nancy I did not see what the limit is on the amount of materials but in this case that works there are 7 materials assigned.

How does everyone deal with instances where more materials need to be assigned? Should one just create a new object in such cases?

Also if anyone could possibly explain why I had the problem with there being no faces that would be great so I can avoid the same mistake in the future. 

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  • 7 years later...

Hi All,

I had this problem, with a mesh that wasn't mine. Turned out that some of the faces/vertices were doubled up so that they would face in both directions and i guess SL just gets rid of one on upload, not always the correct one.

Solved it by merging vertices by distance and then flipping any faces one by one that were facing the wrong way recalculate normals outside after that.

Nevermind, that didn't actually work, but i'm convinced it was part of the problem

Edited by Sasha Ferd
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Hi All, 

 

Found my issue, turns out SL doesn't like it if you have a texture with transparent parts assigned to your mesh, (I was trying to do a car with tinted windows). I made the windows into a separate object and gave them their own texture, made a new no transparency texture for the rest of the car and hasta lasagna it all displayed as expected.

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