Add three-gpu-pathtracer

trees/uts-0018.tree

@@ -40,6 +40,7 @@
 \mdblock{09-23}{
 - more progress on [[ag-000G]], particularly on [[ag-001J]]
 - found [shaderfrog](https://shaderfrog.com/)
+- found [three-gpu-pathtracer](https://github.com/gkjohnson/three-gpu-pathtracer) and related projects, particularly [Physically Based Materials](https://gkjohnson.github.io/three-gpu-pathtracer/example/bundle/index.html), and that [Steve Trettel](https://x.com/stevejtrettel) uses it to render black holes and Hopf fibrations
 }
 
 \mdblock{09-22}{