Merge branch '1.6_maintenance'

Author: murraystevenson

.github/workflows/main.yml

@@ -319,7 +319,7 @@ jobs:
     - name: Install RenderMan 26.4
       run: |
         rm -r "$RMANTREE" # Free up precious disk space from the previous installation
-        ./.github/workflows/main/installRenderMan.py --version 26.4 --dailyBuildDate 2026-06-16 --outputFormat "RMANTREE={rmanTree}" >> $GITHUB_ENV
+        ./.github/workflows/main/installRenderMan.py --version 26.4 --dailyBuildDate 2026-07-16 --outputFormat "RMANTREE={rmanTree}" >> $GITHUB_ENV
       shell: bash
       env:
         RENDERMAN_DOWNLOAD_USER: ${{ secrets.RENDERMAN_DOWNLOAD_USER }}

Changes.md

@@ -354,14 +354,29 @@ Build
 - TBB : Updated to version 2021.13.0.
 - USD : Updated to version 26.05.
 
-1.6.x.x (relative to 1.6.20.1)
+1.6.x.x (relative to 1.6.21.0)
 =======
 
+
+
+1.6.21.0 (relative to 1.6.20.1)
+========
+
+Improvements
+------------
+
+- SceneWriter : Added `IECOREUSD_WRITE_CONFORMANT_RENDERMAN_ATTRIBUTES` environment variable. When set to a value of `1`, `ri:` prefixed attributes are written to USD in a format compatible with `hdPrman`, for rendering with RenderMan in `usdview` and other Hydra-based applications.
+
 Fixes
 -----
 
 - RenderMan : Fixed handling of V3f data with non-geometric interpretation. Common sources include `float3` primvars and attributes loaded from USD files.
 
+Build
+-----
+
+- Cortex : Updated to version 10.6.7.0.
+
 1.6.20.1 (relative to 1.6.20.0)
 ========