Black faces (tried with normals already)

Hi I am experiencing these weird faces coming black…
Normals are fine. I also erased the faces and re built them…and they come like that.

weird faces

Do you know what it could be? I am using ecycles.

If normals are ok and ther eare no spurious edges / faces causing shading issues.
Check for custom split normals, clear them if they exist. Check if auto-smooth is activated and what your smoothing angle is, 90% of the time, setting auto-smooth on and an angle of 35 degrees tends to sort this kind of issue if I get it.

Thank you . How to check spurious edges ? ? Maybe is that?

For edges, I normally just do a merge by distance. You can also try select by trait → loose geometry in edge mode. A manual way I check is by going into face mode, hid the polys I know should be there and see if I can see any odd edges. (A classic case where this happens is converting a text boject with the letter ‘T’ in it to a mesh, it leaves some odd edges in its solve).

I tried checking vertex and re building the faces (different techniques) and its not that. It looks like it has to do with this:
vertex star

As soon as I join the vertex from the face to the other ones …it becomes black.

Sorry no, its not.
I tried with the knife tool…and behaves the same…

I really dont know what the hell is happening.

Can you upload a blend file with that one object in? See if I can do some problem solving?

brokenbuilding.blend (914.2 KB)

Someone had a similar issue in the past. They solved it by moving their objects closer to the world origin 0,0,0. Your object is about 4.3km or 2.6 miles away from it.

It seems somehow, in your case, tied to the objects Y coordinate. Moving it even a little in Y makes the issue disappear. Having said that a little in terms of the size of this object is in the region of 10 or 20 metres. Is your object a two storey building? It’s 160m tall.

Yes, the scale is like that cause I am doing a scene with different things happening…those things have different scale…and the scene needs to show them all in one frame…so if you have airplanes, vessels and trucks …plus a factory…and I make everything at the real scale…it mean that the factory will be a pixel big if it was 20 meters next to a huge vessel. I understand what you say and I generally work with real scale things…but in this case I have fields and different things that all need to communicate at the same level…

So If I need to move my things closer to the origin…then I need to re keyframe everything.

Scale of scenes are always an issue when they get larger.
At some point you have to switch to meters, kilometers or larger for your dimensions.
e.g. you’re not going to model the solar system in real world units like meters. :wink:

What about creating everything in scale, but scale and assemble as needed in hierarchies.
So a top Empty that contains all scaling values, it shouldn’t affect animation inside the hierarchy that way.

Also, too small a scene or too large will eventually affect the renders due to rounding errors. Age old issue :wink:

Looks like your distance leads to a numerical stability problem for the given precision within the calculations done in cycles. If your scene allows it, simply turn the object slightly. ( or the whole scene, or just the wall)

Or put a plant in front. :grin:

Edit: Was having another look at this and stumbled upon a quick fix for you. Change the origins y coordinate to something near the wall itself, that fixes your problem without changing the vertex positions in the scene.

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I will use your tip @Debuk . Thank you .

@RobWu Do you think changing the units to meters will solve all these type of issues? That could be great. I always work with mm , but I did not realize to change it for this scene. I could set the scene units to M if that will solve glitches.

Regarding the empty solution. You mean using the real scale of the mesh for example and parent it to an empty that will be scaled up or down without taking in count the real scale?

@Bruno_Suraski
As far as I understand it all, it has to do with rounding errors in the render egine(s).
At some point the scene get’s too small or too big, and it will mess with the math.
Changing to another unit will ‘move the comma’ so to speak.

And yes. the Empty will drive the overall scaling.
So you can have something in world scale values, parent it under a Empty and scale that the Empty.

I see a lot of Blender artists ignoring the Scene based hierarchy options, and doing all work within Collections.
One, you cannot move/scale these, and two it makes for sloppy scene overview.
Also, splitting things up in Empty based hierarchy parts makes it easier to animate separate parts.
And of course you can move full hierarchies to Collections for rendering later if you want.
We do this all the time with CAD based models.

Hope it helps,

rob

Thanks so much Rob. I am also having some kind of glitch when light becomes shadow…it starts making dark squares…I hope I can solve it with your tips.