demo_canvas API

Luna-Flow/geometry3d/demo_canvas is a browser executable for the js target. It exports no MoonBit items; its interface is the HTML page it expects and the scenes it draws with the Canvas backend.

Build and serve

just canvas-build   # moon build src/demo_canvas --target js, then copy files
just canvas-serve   # build, then serve target/canvas-demo on http://localhost:8080

canvas-build copies src/demo_canvas/index.html and the compiled demo_canvas.js (as demo.js) into target/canvas-demo/.

Page contract

geometry3d-canvas

The page must contain a <canvas id="geometry3d-canvas">. The program sets its width and height attributes to 640 × 480 and draws into its 2D context. The program aborts at start-up if the element or the context is missing.

demo-select

The page must contain a <select id="demo-select">. Its value dolly selects the dolly-zoom scene; any other value selects the torus. The program reads the value at start-up and on every change event.

Scenes

Torus

The torus scene shows a torus with radii 1.7 and 0.58 (32 × 18 segments), turning by $0.0006$ rad per millisecond of the animation timestamp about $x$, $y$ and $z$ in the ratio $0.7 : 1 : 0.25$. The camera is 6.2 units away with a 35 mm lens on a full-frame sensor.

Dolly zoom

The dolly scene is the scene of the terminal demo’s --dolly mode, with the frame number derived from the animation timestamp at 30 frames per second.