Tangent to Two Circles / Mike Bostock

Visualization toolmaker. Founder @observablehq. Creator @d3. Former @nytgraphics. Pronounced BOSS-tock.

Published

Edited

Jan 8, 2022

7 stars

Tangent to Two Circles

function place(a, b, c) {

const x_ba = b.x - a.x;

const y_ba = b.y - a.y;

const l_ab2 = x_ba ** 2 + y_ba ** 2;

const r_ac2 = (a.r + c.r) ** 2;

const r_bc2 = (b.r + c.r) ** 2;

const t_ap = (l_ab2 + r_ac2 - r_bc2) / (2 * l_ab2);

const t_pc = Math.sqrt(r_ac2 / l_ab2 - t_ap ** 2);

c.x = a.x + t_ap * x_ba + t_pc * y_ba;

c.y = a.y + t_ap * y_ba - t_pc * x_ba;

return c;

}

A = ({x: 120, y: 150, r: 50})

B = ({x: 300, y: 205, r: 90})

C = place(A, B, {r: 50 - Math.cos(now / 5000) * 14})

C2 = place(B, A, {r: C.r})

p = {

const x_ba = B.x - A.x;

const y_ba = B.y - A.y;

const l_ab2 = x_ba ** 2 + y_ba ** 2;

const r_ac2 = (A.r + C.r) ** 2;

const r_bc2 = (B.r + C.r) ** 2;

const t_ap = (l_ab2 + r_ac2 - r_bc2) / (2 * l_ab2);

const t_pc = Math.sqrt(r_ac2 / l_ab2 - t_ap ** 2);

return {x: A.x + t_ap * x_ba, y: A.y + t_ap * y_ba};

}

color_a = "#1f77b4"

color_b = "#2ca02c"

color_c = "#000000"

color_p = "#d62728" // d3.schemeCategory10[3]

Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.

Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.

Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.