Has anyone figured a fast way to get decent polygon normals out of Moi ? I mean normals that all face in the same direction ? I've been trying to fix an object with the "flip" command for the past few hours, but I can't seem to figure out how this is supposed to work.

I select a few faces that get exported to Obj in the wrong direction, hit the "flip" command. Export again to check what if they have been flipped ( or is there a way to visualise this in Moi ? ) and nothing has changed.

I then tried "disconnecting" the faces that need to be flipped before using the flip command. When I then export to Obj with only the flipped faces, all looks okay. But when I then join all surfaces again I get flipped normals again.

I can usually work around the problem by using double sided surfaced in Softimage. But for metallic and glass materials the surface normal is important. I have to use a metallic shader, and the flipped polygons render black in Redshift.

I could flip the plygons afterwards in my 3D program, but then I can no longer use the "user normals" that get exported with my mesh.

There must be a better way to get uniform polygon normals out of Moi...yes ?

Thanks,

-Ronald

Hi Ronald, the easiest way (other than just enabling double sided materials like you mention so you usually don't need to worry about it) is to make your object a solid in Moi instead of open surfaces. When your object is a solid it will have its normals automatically oriented towards the outside of the solid volume.

If it's not easy to make your object a finished solid, then the next best thing is to make sure the surfaces are at least all joined to one another - don't have just individual separate surfaces sitting alongside each other, make sure to use the Edit > Join command so that those surfaces are one joined structure that have shared edges between each surface.

When surfaces are joined together the mesher will take care to orient the mesh faces for each surface in one consistent direction. If that ends up not being the correct direction you can then flip the whole thing in one go to correct it rather than trying to flip individual separate pieces.


> I could flip the plygons afterwards in my 3D program, but then I can no longer use the
> "user normals" that get exported with my mesh.

It's kind of strange that they don't just flip the user normals at the same time as the polygons are flipped...

In the past I have assumed that if a program is sensitive to the particular normals direction that they would have some tool included with it to flip it properly, but sadly that seems to be often not the case.

- Michael

Hi Michael,

Thanks for the fast reply.

Is there a separate command to create a solid ? I joined all surfaces and assumed that creates a solid, but the normals are still not aligned.

This is what the Obj looks like in Softimage:


When I then flip the polygons in Softimage, I have to delete the included usernormals to see the result. Otherwise flipping the normals has no effect. But when I don't use the usernormals I get smoothing artifacts. The solution would be to export a extremely high rez Obj, but that's not always an option.

You can see the smoothing artifacts after flipping the polygons in Softimage and deleting the usernormals in this image:


I've put the .3dm file here as well : https://www.dropbox.com/s/fgtzf2qw8eqdqao/montage_3_poot_final_v02.rar?dl=0

Thanks again,

-Ronald

Ah, I found a command to flip the usernormals in Softimage. That seems to solve the problem for now :-)

Thanks,

-Ronald

Hi Ronald,

> Is there a separate command to create a solid ?

No, just if you join together all pieces that touch each other so that all edges are joined between 2 surfaces, that makes a solid. When you have a solid, it will read as a "solid" as the object type in the properties panel:


If it reads as a "Joined srf" or "Surface" rather than "Solid" then it means there are some holes in the model where edges are not aligning closely enough with each other to get joined. To see where those edges are you can set up a "Select naked edges" script on a shortcut key as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=6051.2


> I joined all surfaces and assumed that creates a solid, but the normals are still not aligned.

I think it's because there are some squished down degenerate surfaces in there as well. If you have surfaces with self-intersecting trim boundaries or surfaces that are effectively squashed down to a line with no surface area those kinds of things can mess up the face traversal that the meshing mechanism uses to keep consistent face normals.

Here's one such little slivery surface that I found here:







> Ah, I found a command to flip the usernormals in Softimage. That seems to solve the problem for now :-)

Good!

- Michael

Great, thanks for the tips. When I look closely I see a lot of suspect surfaces like the one you pointed out.

I did a lot of the filleting in Viacad because Moi refused to. I think that was bad idea after all, it probably created a lot of the messy faces.

Looks like I have some cleaning up to do.

Thanks,

-Ronald