Mirroring / Flipping component , normals

#1

Hello. I have 2 components A and B.
B is the same as a A but it has been flipped on green axis.
After exporting to Blender and then to Substance Painter the flipped component (B) has its normals inside out.

Is there any way to flip/mirror components without messing their normals up ? I have tried mirroring the component in 3-4 different ways but the result was the same…

Also is there a way to see if the normals are wrong in Sketchup ? I thought if they are, then the faces will appear as blue.

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#2

What if you explode B > then make it a component again. It will have its new axes according to the system’s axes again, not mirrored axes

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#3

I blame this on Blender/SubstancePainter or the importer. Flipping something reverses the winding order of the faces, thus reversing the normals. SketchUp is wisely designed, knows when an object is flipped (has a determinant less than 0) and compensates for the reversed normals. Somewhere this isn’t done when importing to Blender.

Does Blender recognize the two objects as identical, i.e. sharing some kind of definition, or are they just two separately defined meshes?

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#4

Wo3Dan I thought of this but I want to have the same component in blender and then make the UVs just on it rather than to several ones. ( I know that its possible to transfer UVs to identical geometry but so far the other way is faster)

eneroth3 Hmm. Maybe you are correct , I do use several plugins.
To get the model from Sketchup to Blender I use this Blender plugin: “https://github.com/martijnberger/pyslapi/releases” It takes the entire Sketchup file and puts it into Blender. I use it because it retains the separate components just as they were from Sketchup. Do you know any other way to export from Sketchup and retaining the components ? If yes I can try and see if the plugin is the issue.

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#5

I have no experience with Blender, but does it treat these two objects like instances of one and the same thing the way SketchUp does? If not I think you should be able to flip the normals on one without the other being affected.

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#6

Unfortunately it does , so changing just one is not possible. I can do some tedious workaround in the way I mentioned above to Wo3Dan but for big/complex models it is going to take forever to do…

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#7

If so I would say this is a problem in the Blender core. What happens if you create objects within Blender that has the same kind of relation (what is the equivalent of a component even called in Blender?) and flip one of them? Do you see the same reversed normals then too?

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#8

I am not sure how its called either , I use it primarily for uv editing. I am watching some tutorials about it now though. Will write later with the results. Thanks for the help btw.

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#9

eneroth3 Yes you were right , it is a Blender Issue. From what I understood in Blender they just reuse the same mesh in other components. So when you mirror it , it doesn’t take into account the normals and just flips everything. I will go on tinkering with Blender in that case or write into their forum if I cant find a solution. Anyway thanks again.

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