calibStepRamp

A procedural calibration ramp for the materialLibraryKit calibration shelf: the surface is cut into steps discrete patches across U, and each patch sets one PBR channel — roughness (channel = 0), metallic (channel = 1) or albedo (channel = 2) — to a value stepped from low (left) to high (right), linearly or, with geometric = 1, in equal ratios. Thin dark dielectric separators (separator_width, separator_color) frame every patch so the steps read under any light. The channels that are not ramped take base_color, roughness and metallic. It is an engine-lit surface() shader with no textures, so the capture tool's roughness, metallic and albedo passes show exactly the stepped values each patch carries. Used by roughnessRamp, metallicRamp and albedoRange.