Random lines

[boxfx]

This has bugged us for years, does anyone know how to get rid of these random shading lines? They occur when we use a noise at a small scale to make scratchy plastics and metals, especially when there is light hitting it at a slight angle to show this roughness visually.

They vanish if you disable the bump channel, and move their position on the model if you move or rotate the texture projection on the mesh. We can move the texture so this shot looks good, but that means they will appear somewhere else on the mesh when we move the camera.

[Tim_Twisted]

-Do you use network rendering or multiple gpus?
-Does ray epsilon change the appearance or location of the line?
-Does camera movement have an effect?

[DinoMuhic]

This has bugged us for years, does anyone know how to get rid of these random shading lines? They occur when we use a noise at a small scale to make scratchy plastics and metals, especially when there is light hitting it at a slight angle to show this roughness visually.

They vanish if you disable the bump channel, and move their position on the model if you move or rotate the texture projection on the mesh. We can move the texture so this shot looks good, but that means they will appear somewhere else on the mesh when we move the camera.

Screenshot 2025-04-29 145118.png

Hey there,

I am pretty sure this is coming from your Cubic projection that you have set in the Material tag.
Since you are projecting this way but your polygon is tilted you are introducing a seam there due to the tiling of the noise and which happens to "cross" the polygon. You can observe this by turning on the texture mode in C4D and then moving the projection around (keep the material tag selected).

My advice: for such effects: it would be better to use a 3D projection for the noise since it will not tile, like "XYZ to UVW" in the octane projection node. Switch the material tag back to "UVW Mapping" for this.
You might need to change the noise power though to dial the strength down again. Other options are UV mapping, but for this you would need correct UVs everywhere, which I know is a pain. But for such things "XYZ to UVW" works best.

Best
Dino

[boxfx]

-Do you use network rendering or multiple gpus?
-Does ray epsilon change the appearance or location of the line?
-Does camera movement have an effect?

They show up with a single or multiple gpus. If you're thinking they're the edge of a bucket, they're not, they move around with the texture projection and can be diagonal depending on lighting positions.

Ray epsilon has no effect on this issue

Camera position only affects it in so much that it changes the reflection. The line itself will stay stuck to the 3d mesh / material projection. ie the line doesnt move when the camera angle changes.

[boxfx]

This has bugged us for years, does anyone know how to get rid of these random shading lines? They occur when we use a noise at a small scale to make scratchy plastics and metals, especially when there is light hitting it at a slight angle to show this roughness visually.

They vanish if you disable the bump channel, and move their position on the model if you move or rotate the texture projection on the mesh. We can move the texture so this shot looks good, but that means they will appear somewhere else on the mesh when we move the camera.

Screenshot 2025-04-29 145118.png

Hey there,

I am pretty sure this is coming from your Cubic projection that you have set in the Material tag.
Since you are projecting this way but your polygon is tilted you are introducing a seam there due to the tiling of the noise and which happens to "cross" the polygon. You can observe this by turning on the texture mode in C4D and then moving the projection around (keep the material tag selected).

My advice: for such effects: it would be better to use a 3D projection for the noise since it will not tile, like "XYZ to UVW" in the octane projection node. Switch the material tag back to "UVW Mapping" for this.
You might need to change the noise power though to dial the strength down again. Other options are UV mapping, but for this you would need correct UVs everywhere, which I know is a pain. But for such things "XYZ to UVW" works best.

Best
Dino

It isnt the diagonal cubic mapping cutting through the polygon. If you take this scene and add a fresh c4d cube then move the texture tag over, youll see you have a perfectly straight cube with no material rotation, but you still get the line.

Will give the xyz option a go, but I remember we were having trouble elsewhere with this when applying extra materials on top with flat projections. eg a rough metal surface with a label or screen printed artwork on top.

[DinoMuhic]

With some help we identified the issue: Your material is using a 2022.1 compatibility mode. But this issue was fixed after 2022.
So you need to remove that and set it back to the current version in the Materials basic tab, and then use the bump height slider to adjust your bump scale.

[boxfx]

Works, thanks!. The only other thing which I may as well ask now, why does the bump channel always need such a tiny value to work? The default value is already 0.02, but I find that useless for absolutely everything, instead I have to start of way down at like 0.00002 But this brings another problem with it, this is already the precision limit for octane / c4d. ie 0.000021 is identical to 0.00003 because something is rounding up the 21 to 30, it only seems to have 5 decimal places of precision.

If you open the same project attached at the top, switch it to 2025 compatibility mode and set the bump to 0.00002 You can see this is almost identical to the bump strength I had before, but its a little too low, it needs to be 0.000021 or 0.000022. But you can't use these values as they all get rounded up to 0.00003 which is too high.

[DinoMuhic]

Hey yeah we can look into it if we can stop c4d from rounding it up. In the meantime you can just go into the noise itself and just increase the power of the noise to like 0.6 while keeping the bump height at 0.00002