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Old 02-05-2013, 04:04 PM   #1
hikarubr
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Selecting polygons with the same normals

I've been using some imported Sketchup models in my last projects. They tend to come with the normals mixed. I've tried to use the align normals command to fix it, but it just doesn't.

So I've been fixing each model manually, selecting the inverted polygons and reversing the normals. Needless to say, that's very boring.

Is there a way to simply select all the polygons with the same normal direction? So I could just select the ones with inverted normals (the ones that show as blue when selected) and then invert them?

If that's not possible in Cinema 4d, is there a plugin or script that does that? Or could some one help me with some python tips about how could I write such script?

Thanks
 
Old 02-05-2013, 07:18 PM   #2
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c4d has a phong select which is a normal based selection, but the selection will end at your normal tolerance, so this won't do what you want. For your task you should use the align normals command in the polygon menu. Sometimes you have to run a reverse normals command afterwards, because align normals follows a funny logic to determine which is the the desired normal direction (you could also say it is a bit buggy ).
 
Old 02-05-2013, 07:28 PM   #3
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Yep. What Little_Devil said.

Anytime my normals are scrambled arbitrarily (or any other reason), I select all the polygons of the mesh, hit Align Normals, and that will force all normals to face in or out. If they're pointing the opposite direction than desired, then just apply Reverse Normals.

Works every time.
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Old 02-05-2013, 09:30 PM   #4
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Quote:
Originally Posted by cmyk
Yep. What Little_Devil said.

Anytime my normals are scrambled arbitrarily (or any other reason), I select all the polygons of the mesh, hit Align Normals, and that will force all normals to face in or out. If they're pointing the opposite direction than desired, then just apply Reverse Normals.

Works every time.


Well, this usually works for me too, but not in this case. As I said in my original post, for some reason this is not working with the models that I import from Sketchup (they are exported from Sketchup as collada files). I don't have any idea why it's not working
 
Old 02-05-2013, 09:59 PM   #5
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try to see if you can pull into Blender, and how it handles it, and then re-export it out. maybe something else can handle the export better.
 
Old 02-05-2013, 10:13 PM   #6
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Quote:
Originally Posted by hikarubr
Well, this usually works for me too, but not in this case. As I said in my original post, for some reason this is not working with the models that I import from Sketchup (they are exported from Sketchup as collada files). I don't have any idea why it's not working


Perhaps there's some detached faces? Try selecting all the vertices in point mode, then use the Optimize command to make sure all vertices are welded together. Then see if the align/reverse normals trick works.
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Old 02-05-2013, 11:02 PM   #7
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Quote:
Originally Posted by hikarubr
Well, this usually works for me too, but not in this case. As I said in my original post, for some reason this is not working with the models that I import from Sketchup (they are exported from Sketchup as collada files). I don't have any idea why it's not working



If align normals is not working, sometimes there is also a hidden polygon somewhere.
 
Old 02-06-2013, 07:04 AM   #8
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iv seen imported files which have polygon errors.(c4d cant read them)
try deleting the bad polygons then adding them back
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Old 02-06-2013, 08:17 AM   #9
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In those cases i usually do the following
1. Optimize
2. Align normals

If those don't work chances are you have holes, illegal geometry (thrice used edges, collapsed polygons) or simply disonnected parts.
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Old 02-06-2013, 08:17 AM   #10
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