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Old 25th October 2022, 08:00 PM   #1
avesthefox
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Question Surfaces are black and I dont know why :/

So what does it usually mean when a surface goes black like this? I cant seem to change it so I am assuming its an error in the model that needs adjusting?

Generally this seems to happen after performing boolean stuff in AC3D, or importing it from Blender after doing some very complex boolean stuff over there that AC3D cant seem to handle (I use AC3D mainly for very simple primitive boolean commands). :P
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Last edited by avesthefox; 25th October 2022 at 08:19 PM.
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Old 27th October 2022, 10:51 PM   #2
maineman
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Default Re: Surfaces are black and I dont know why :/

I believe this happens when you create an object with two sides and the normal is wrong. Try changing the normal on that one surface and see if it changes.
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Old 27th October 2022, 11:58 PM   #3
avesthefox
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Default Re: Surfaces are black and I dont know why :/

Quote:
Originally Posted by maineman View Post
I believe this happens when you create an object with two sides and the normal is wrong. Try changing the normal on that one surface and see if it changes.
I have played around with the normals. Nothing changes
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Old 28th October 2022, 12:58 AM   #4
maineman
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Default Re: Surfaces are black and I dont know why :/

from the manual

"Change vertex order"

This changes the order in which the vertices of a surface are drawn, by moving the first vertex to the end of the vertex list. This can be used to change the position of a break in a line. It can also be used to fix a bad polygon, which has the first three vertices in a non anti-clockwise order - causing the normal (used for lighting) to be incorrectly calculated. If a polygon appears all black, this function may need executing (possibly repeatedly) until it appears correctly."

and

"It is possible to combine surfaces that do not lie on the same plane. It is recommended that the vertices be flattened in order to make them lie on the
same plane.

If after combining surfaces, the new surface appears black from every angle, this means that the first three vertices of the surface form an angle of more than 180
degrees. To prevent this, the vertex order must be changed (Surface->Change Vertex Order) so that the first three vertices of the surface form an angle less than 180 degrees."
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Old 4th November 2022, 05:07 AM   #5
Andy
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Default Re: Surfaces are black and I dont know why :/

Yes, maineman posted the solution. It might be best to triangulate this surface.


Essentially, the surface normal is calculated using the direction of the first three vertices of a surface, so some convex shapes can lead to a confused normal.
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