Description:
When importing smooth, untextured meshes into Roblox Studio, prominent dark shading lines and creases appear permanently across flat or curving polygons.
This behavior appears to be an engine-side rendering conflict tied to the high-precision Screen-Space Ambient Occlusion (SSAO) or depth-buffer pass at maximum graphics. The artifacts occur entirely independently of the mesh’s UV maps, vertex color channels, or modeling layout (seams/sharp flags).
The lines are completely invisible inside the 3D Import Preview window, but generate immediately in the workspace once the camera gets close to the object. Textures merely mask or scatter the visual appearance of these lines, but an untextured view reveals that the workspace viewport generates pixelated shadow cracks along the underlying triangle boundaries of clean assets.
Step-by-Step Instructions to Reproduce:
- Open Roblox Studio and ensure settings are configured to Editor Quality Level 21.
- Import an untextured, smoothly shaded mesh (the issue is present on both clean quad layouts and pre-triangulated files) via the 3D Importer.
- Observe that the asset looks completely clean and uniform inside the 3D Import Preview window.
- Generate the asset into the Workspace and move the viewport camera up close to the mesh surfaces.
- Observe distinct, sharp black shadow lines running along the geometric face paths.
- Move the camera backward and forward; notice that the shadow lines artifact by blurring and shimmering rather than scaling smoothly.
- Lower the Editor Quality Level to 20 or below; the shadow lines instantly disappear.
Isolations Disproving Asset/Topology Error:
- Polycount Impact: Pushing the mesh from 3.5k triangles to a higher resolution quad-remesh significantly alters and reduces the artifact patterns, but faint lines still persist along the new topology flow. This indicates the engine’s up-close shading calculations remain highly sensitive to underlying triangle layout changes even at higher polygon densities.
- Independent of Environment Shadows: Turning off
CastShadowor rotating the mesh away from the global light source does not move, alter, or remove the lines. - Universal Behavior: Testing professional, highly optimized game-ready assets (like a dragon head model) without textures reveals the exact same up-close shading discrepancies along the triangle edges.
Examples:
Black lines on left man 14k tris mesh which is a smoother, originally quad topology, of the man on the right with 3.5k tris:
Untextured dragon head showing the creases:
Dragon head in blender showing topology:
Lines shimmering and blurring:
Expected behavior
When viewing smoothly shaded geometry up close at maximum graphics quality, the surface lighting calculations should remain unified and seamless. High-precision screen-space passes should ideally apply ambient occlusion cleanly without generating precision shadow creases along flat or continuously curved triangle transitions.
As a reference, when this exact same optimized mesh is imported into Unreal Engine 5 under high graphics settings, it renders uniformly with zero dark artifact lines or depth creases along the polygons.
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