The lamp and the zero
Your pointer is a lamp. The zero’s shading turns to face it and its shadow swings away, worked out line by line.
Move the pointer over the sheet, or drag a finger. The slider walks the lamp round the zero for the keyboard.
How it works
The zero is a ring with thickness. For every point along every hatch line I keep which way the surface faces there. When the lamp moves, one sum per point says how much light it gets, and the line is drawn only where it should be dark. Nothing is hatched again: the lines are fixed, and the light picks which bits of them show.
The shadow is worked out from the ground’s side. A point of the paper is in shadow when the ring stands between it and the lamp, so a lamp further off throws a longer one, and a lamp over the hole lights the inside wall.
By night the paper is dark and the ink is chalk, so the test turns round: the hatch goes on the lit faces. Switch the theme and look.
- Input
- Pointer, a dragged finger, or the slider
- Drawn with
- One canvas, five strokes
- Work
- A few tens of thousands of sums, only when the lamp moves
- Reduced motion
- The same; the lamp never moves by itself
Made for the fun of it. The paid work gets the same pen.