AnyImage/openspec/changes/archive/2026-09-17-scale-tangent-normals-with-depth/proposal.md

Why

Tangent-space normal maps describe the full-depth surface. When a geometry node reduces its Depth Scale, its shape becomes flatter but the material normal remains at full strength, making surface detail appear too strong.

What Changes

• Reuse the existing o_normal_reduction geometry attribute as the material-to-geometry contract for tangent-space normal strength.
• Make tangent-normal depth geometry write 1 - Depth Scale to that attribute, so the material normal strength follows the displayed geometric depth.
• Extend the existing O Image Layer behavior without changing its attribute lookup or fallback semantics.
• Make Object Space normal strength follow the same geometry reduction contract.
• Reuse the existing o_normal_reduction contract for additional Tangent-normal depth geometry.

Capabilities

New Capabilities

• depth-scaled-tangent-normals: Keep tangent-space material normal strength consistent with geometry depth scaling.

Modified Capabilities

None.

Impact

• Tangent-normal geometry-group builders, especially Relief Plane.
• Normal-scale node tests; saved node assets must be rebuilt with uv run node-group build.
• No server inference format, user-facing modifier socket, or dependency changes.