View Full Version : Normals

11 November 2006, 05:17 PM
I need a way to easily find 'flipped normals' or 'normals that are not consistant with 99% of the other meshes normal direction' in the viewport, not renderer.

I know you can use “Display Normals” in your Polygon display options but on most meshes this is completely useless and is sometimes like finding a needle in a hay stack!

The only way I can think to make finding these easily is to assign a double sided shader with two distinctly different colours and then render. Can anyone suggest a viewport method without the time lag of rendering?



11 November 2006, 02:12 PM
Well there shouldn't be much of a reason to have inverted normals in the first place. However, once you're there, it's pretty much picking the needle in the haystack if you've got a highpoly mehs, unless you try this nice trick:
In Edit Poly, go to Border sublevel, and then with drag and drop ( not CTRL-A for select all ) go over the entire mesh, and each inverted face will be seen as a border and get selected. This way, with F4, you can see where you've selected borders, and you can proceed and flip each one respectively.

To render faster, you can deactivate Filter Maps, Antialiasing, Shadows and Mapping alltogether ( F10 for the Render Scene window, then Renderer tab ).

11 November 2006, 02:35 PM
Yeah I don't want the flipped normals there for any reason, I just need to make absoltuely certain they have been removed before the assets get passed on to other deps. I have a simple script which automatically selects and highlights border edges so they appear orange instead of green.

Selecting border edges only highlights non-manifold geometry and can't distinguish between a full mesh with normals facing the wrong direction...hmmm, I'll try and exlain it another way.

Say you have a fence with 100 bamboo sticks closely aligned to one another.
How do you find the one bamboo stick with all its normals facing the opposite direction to the other 99?

The only way I can think is to render, which I would like to eliminate as an approval process...was just hoping someone knew of a trick you could use to check for this in the viewport.


11 November 2006, 09:49 AM
Try this....under lighting menu (viewport menu), turn off two sided lighting. This will render all flipped faces black in the viewport. I also think there was a flipped normals selection script in Maya 7.0 bonus tools.....

11 November 2006, 11:31 AM
...genius! Great tip vvmanoj.

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