Surface normals not preserved on "Divide selected shapes"

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mfloyd
Posts: 21
Joined: 29 Oct 2014, 23:06

Surface normals not preserved on "Divide selected shapes"

Post by mfloyd » 08 Aug 2015, 00:48

After importing a .obj and then using the "Divide selected shape" option, shapes that used to have a 'smooth' curved surface become faceted. I am assuming that this is because that operation does not preserve the surface normals associated with the original vertices that make it display nicer.
Removing points from the mesh in shape edit mode (in order to manually separate parts) does the same. Even opening the part in shape edit mode and not changing anything, but accepting the "changes" when exiting shape edit mode causes the appearance of the part to be changed. Extracting a shape does preserve the smooth appearance, but then the color and texture map won't transfer to the extracted shape. For a shape that doesn't have a special texture map, but only standard color, the color can be transferred when selecting "Apply to selection" under the Colors section of the shape dialogue box. I've found in the past that removing points would preserve a texture map with imported texture coordinates, but apparently doesn't preserve the smoothness.

coppelia
Site Admin
Posts: 7123
Joined: 14 Dec 2012, 00:25

Re: Surface normals not preserved on "Divide selected shapes

Post by coppelia » 10 Aug 2015, 07:47

Hello,

you are right. What is actually happening: the shading angle specified for a shape will be used to actualize the appearance of that shape if it was modified in any way.

Cheers

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