The demo is published on this page.
A demo very similar to the Mandelbrot demo but with ray tracing, which requires even more computation resources.
This demo demonstrates how you can reuse some Java code from existing JavaFX applications. For example, The ray tracing computation code was taken from this JavaFX application.
Since JavaFX was not originally designed for the web, WebFX provides some additional APIs to work with web-specific concepts such as web workers and WebAssembly modules, which can be useful for applications requiring heavy background tasks. WebFX can interact with third-party web workers and WebAssembly modules or you can write your own in Java. In this demo, they are written in Java and compiled with TeaVM.