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Comment by kristopolous | Hacker News Reader

How would projection code get you rotational animation for free?

The projection logic has an orientation parameter (which you'd probably always want, so that you can pick initial rotation), so the rotation animation itself is just updating the param on a timer.

Basically line 182 plus the calls to redraw:

    gamma -= 0.003;

To do it with CSS, at a minimum it would require adding support for rendering to two different canvas elements.

> To do it with CSS, at a minimum it would require adding support for rendering to two different canvas elements.

It might into trouble because rotating a rectangular <img> area varies it in height and width [1], but I would investigate animating a ‘rotate’ transformation. https://developer.mozilla.org/en-US/docs/Web/CSS/transform-f....

[1] seems to have a demo without that problem, so it seems this can be made to work https://imagekit.io/blog/image-rotation-html-and-css-imageki...

Here's an interactive WebGL implementation: https://brian.sh/around/index.html

It doesn't have a satellite image option, but that would arguably be simpler than drawing continents like it does now. It uses a seldom-redrawn base canvas (menu -> debug > show 2d texture) then the discs are drawn with a simple shader.

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