Update dataset card: appearance section and change list

README.md

@@ -26,6 +26,10 @@ Each folder is a SimReady package: the USD asset in `simready_usd/`, thumbnails,
 
 Both assets pass the SimReady **Robotics-Prop 4.0.0** profile (simready-validate 2026.8.0) and the simready-benchmark runtime tests in Isaac Sim 6.1 (PhysX and Newton sessions). Results are included in each package.
 
+## Appearance
+
+Colour zones follow the official product photos. Every material has a UsdPreviewSurface and an OpenPBR (MaterialX) surface; renderers that do not read MaterialX use the UsdPreviewSurface. In the OpenPBR surfaces the machined metal parts reflect anisotropically and carry a faint pattern of machining marks, both computed in the shader from the object-space position and normal, without UV sets or texture files. Material values are visual approximations, not measured optical properties.
+
 ## Data sources
 
 All data are taken from ZeroErr public material:
@@ -43,6 +47,11 @@ The assets contain the external shape and published parameters only. They do not
 - The split of mass between housing and output flange uses the published output-side mass and inertia; the output-side centre of mass and transverse inertia are estimates. Details are in the asset metadata.
 - Gear friction, efficiency and backlash are not modelled.
 
+## Changes
+
+- 2026-11-10: appearance update (materials and thumbnails). Geometry, mass properties, joint and brake parameters are unchanged.
+- 2026-11-09: first public version.
+
 ## License
 
 [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). Attribution: **ZeroErr** (https://www.zeroerr.com). This license does not grant any trademark or patent rights.