Bevel shaders

A bevel shader makes sharp edges look rounded at render time. It changes the shading normals near each edge, the same way a bump map does, but leaves the mesh untouched. Blender describes its Bevel node as a shader "for rendering rounded corners" that, "like bump mapping", affects only shading (Blender Manual: Bevel Node). Redshift calls its version a shading effect that simulates "round beveled edges but without introducing extra geometry" (Redshift documentation: Round Corners).

In game art, bevel shaders are mainly a shortcut for the the high-to-low workflow: you render or bake rounded edges from a simple, sharp-edged model instead of modeling every bevel. bevels and chamfers compares them with the other bevel methods.

#How it works

Redshift's documentation describes the mechanism: the shader sends probe rays to find nearby edges and corners, and the result is fed into the surface's bump input (Redshift documentation: Round Corners). Shading normals within the radius bend towards the neighbouring faces. The settings follow from that:

• Radius or width: how far from the edge the rounding reaches (Blender Manual: Bevel Node; Marmoset Toolbag documentation: Surface module: Bevel settings; Redshift documentation: Round Corners).
• Samples: how many probe rays per shading point. More samples are smoother and slower (Blender Manual: Bevel Node; Redshift documentation: Round Corners).
• Which objects count: whether separate, intersecting objects round against each other (Redshift documentation: Round Corners; Marmoset Toolbag documentation: Surface module: Bevel settings).

The silhouette stays sharp, so large rounded forms still belong in the mesh.

#Three implementations compared

Marmoset's millimetre width needs correct scene scale: a crate imported at the wrong scale gets bevels ten or a hundred times off. See units, scale and axes.

#Bevel shaders in a game-art bake

Marmoset's own tutorial describes the workflow: generating bevels in the material can "eliminate the time-consuming process of adding edge loops for subdivision control", as "an alternative to creating a detailed subdivision surface mesh" (Marmoset: Revolutionize Your 3D Workflow with Toolbag's…). Toolbag cannot bake directly from the low poly, so you still need a high and low pair; for simple assets, a copy of the low poly with a bevel material can serve as the high (Marmoset: Revolutionize Your 3D Workflow with Toolbag's…). It also warns that shadows still come from the raw mesh, so "harsh shadows can appear" where light should wrap round the edge (Marmoset: Revolutionize Your 3D Workflow with Toolbag's…).

#Limits

• Wide bevels. Redshift says the effect "can't represent extremely wide bevels" and advises small radii; at large radii low sample counts give triangular artefacts near corners (Redshift documentation: Round Corners).
• Blocked rays. Some edges may stay unrounded because the probe rays are blocked by the mesh's own sharp geometry; Redshift suggests traditional bevelling in those cases (Redshift documentation: Round Corners).
• Hidden faces. Internal polygons inside intersecting objects create false edges; delete them or boolean the objects (Redshift documentation: Round Corners). See booleans.
• Cost. Blender calls the node "very expensive", best for baking or stills, and notes that the Bevel modifier "is a faster option when it works, but sometimes fails on complex or messy geometry" (Blender Manual: Bevel Node).

#Related terms

bevels and chamfers · baking · normal map · the high-to-low workflow · the mid-poly workflow · shaders for artists

#Further reading and watching