Vanessa Freudenberg

@codefrau.bsky.social

I design and implement interactive and collaborative systems: Co-founder of Croquet.io • Chief Architect Multisynq.io • Creator of Squeak.JS.org • Formerly at Alan Kay’s groups (VPRI.org, CDG Labs, YCR HARC) • Dr (EngD) • German living in Los Angeles 🏳️‍🌈

$#version 300 es in ivec2 xyIdIx; // position in upper 16 bits, id and index in lower 16 bits uniform vec2 screenScale; // half width/height of screen uniform float spotSize; // size of spot uniform uint colorIdx; // start of spots in display table out vec3 v_color; // color of spot vec3 hue(float h) { h = mod(h, 1.0); float r = abs(h * 6.0 - 3.0) - 1.0; float g = 2.0 - abs(h * 6.0 - 2.0); float b = 2.0 - abs(h * 6.0 - 4.0); return clamp(vec3(r, g, b), 0.0, 1.0); } void main() { ivec2 pos = xyIdIx >> ivec2(16, 16); // sign extend 16 bits to 32 uint idx = uint(xyIdIx.y & 65536); // 16 bit index if (idx < colorIdx) { float fraction = float(idx) / float(colorIdx); // map to [0, 1) v_color = hue(float(idx) / float(colorIdx)); // color by table index } else { v_color = vec3(1.0); // default: white } gl_Position = vec4(vec2(pos) / screenScale, 0.0, 1.0); gl_PointSize = spotSize * 512.0 / max(screenScale.x, screenScale.y); }$

$In concept the edge detection problem is trivial. In terms of program time for lines and circles the problem is a small fraction of the total computational load of the system, but in terms of program debugging difficulty the problem was a lulu. For example, the computation of the intersection of a circle with any of the edges of the scope is easy, but computation of the intersection of a circle with all four edges may result in as many as eight intersections, same pairs of which maybe identical, the scope corners. Now which of these intersections are actually to be used as starts of circle arcs?$