Stuffy is my little tool to quickly do experiment with shader.
Just run cargo run and run.
Since this is a pathtracer, the longer you let it run, the more the picture will converge (be less noisy).
You can move the camera around by clicking and dragging the mouse and with W A S D (sorry azerty user, no time to handle this properly).
The mouse wheel control the aperture (bigger aperture = more bokeh blur / depth of field), and clicking with the right button will set the focus
to whatever is on the cursor when clicked (note: since a bigger aperture will distort the image, focus the right object with a big aperture can be tricky).
To get the parameter of the camera, press I and it will show on the terminal. R will reset the image, holding P pause the rendering, O display the current number of sample rendered, and V zero-out the aperture as long as it is pressed.