Weird black shading


#1

This is a snap of a totally green object. What is that black stuff? I dont have shadows turned on but there is a load of ugly black shading. Can anybody tell me what this is and how to get rid of it please?


#2

Maybe it’s an issue with the mesh normals.
Can you point us to the model?

Ozan


#3

Its not the normals, I checked, it is just a cube subdivided and given some contours.

It is to do with the sunlight or something because these shadows change according to the rotation of the object, and always seem to be dark on the eastern side (-x) even if I rotate the object.

The object is http://lets3d.com/hifi/earth/terrains/terrainhills.fbx


#4

I have noticed similar problems with rendering flat surfaces, and also issues with differences in full screen vs. windowed in win 7 nvidia rendering.

Suspects it has to do with new skybox/atmosphere rendering stuff.


#5

@Adrian, I had a play with your mesh.if u mesh with the depth of it in world ie the middle cubes further apart, the weird shading happens if you press it too flat, so I think its the upper and lower topology pressing through itself( if u watch my hands I’m kinda weaving my fingers together explaining it)


#6

That makes a lot of sense @Judas thanks for that. I did flatten some of them.
@ozan you were probably right, looks like the lower faces showing thru the upper ones causing the reversed normals to appear thru the surface.
I will make some test items but looks like Judas is onto something.


#7

Basically what @Judas demonstrates and said is absolutely correct.

The normals from the bottom are facing down but are relatively faces are relatively flat on it.
When the object is shrinking down to a really flat shape, floating point errors start to arise as the vertice positions become scaled down and down, until it will begin to conflicting with each other so that the “depressions” are lower than the face at the bottom of the mesh.

Once these are lower than the vertices in the bottom of the mesh, they will cast a shadows on the topology that goes below it (because after all they are like little caverns, we just happen to see through the top of it).

So if you want to truly get rid of them at a such a flat plane, either remove the bottom faces, or just avoid shrinking it down to a near planar shape :slight_smile:


#8

Cool. Glad we got some good tips on this.

Ozan


#9

I really love watching you guys problem solve.


#10

I am sad to announce this did not solve the problem.
I recreated the hills and removed the bottom faces and re-uploaded.
As before everything looked great right away but the next time I logged in the shading is back.
It doesnt seem to make any difference about the lower faces, I didnt shrink it down and I have no lower faces so it must be something else.


#11

Well, I guess I will retract my prior admiration… :wink:


#12

After a restart the black shading has changed to a strange green shading, I dont know if this helps at all but here is the latest snap, these models have no bottom faces.

FOUND SOMETHING

This has to do with the zones, with the cloudy sky skybox the shading is pale green but using the tropical daytime the shading is black. and this is repeatable. Something about the zone is causing this shading.


#13

I think it is shadows from the clouds on the skybox. A similar sort of oddity as when text on chat boards cast shadows.


#14

Or maybe you have a light source in your zone shining across the topology that is causing shadows?