The WebGL Tombstone is simple demo app showing how to combine a 2D Canvas, with a WebGL Canvas. Specifcally you can draw on the 2D Canvas and have the 3D tombstone update in realtime.
Just host this directory with a webserver of your choice. You can also use the
webserver.sh script included (provided you have Python) to set up a simple development server.
Then visit http://localhost:5000 in your browser.
This project is based on amd-three.js. Please see there for details of project structure