raphlinus · raphlinus · Nov 12, 2023 · Nov 13, 2023 · Dec 10, 2023 · Dec 15, 2023
diff --git a/_config.yml b/_config.yml
@@ -41,3 +41,7 @@ plugins:
 #   - vendor/cache/
 #   - vendor/gems/
 #   - vendor/ruby/
+
+exclude:
+  - Cargo.toml
+  - Cargo.lock
diff --git a/_figures/.gitignore b/_figures/.gitignore
@@ -0,0 +1,2 @@
+/target
+/dist
diff --git a/_figures/beztoy/.gitignore b/_figures/beztoy/.gitignore
@@ -0,0 +1,2 @@
+/target
+/dist
diff --git a/_figures/beztoy/Cargo.toml b/_figures/beztoy/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "beztoy"
+license = "Apache-2.0"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+console_error_panic_hook = "0.1"
+wasm-bindgen = "0.2.87"
+web-sys = "0.3.64"
+xilem_web = { git = "https://github.com/linebender/xilem", rev = "1ef39fc562d969cfc8548d16b2b72202a5d2196d" }
diff --git a/_figures/beztoy/README.md b/_figures/beztoy/README.md
@@ -0,0 +1,5 @@
+# beztoy
+
+A toy for experimenting with Bézier curves, intended to become a testbed for Euler spiral based stroke expansion.
+
+Run with `trunk serve`, then navigate to the webpage.
diff --git a/_figures/beztoy/Trunk.toml b/_figures/beztoy/Trunk.toml
@@ -0,0 +1,4 @@
+[build]
+#public_url = "https://levien.com/tmp/beztoy/"
+
+
diff --git a/_figures/beztoy/beztoy.tar.gz b/_figures/beztoy/beztoy.tar.gz
diff --git a/_figures/beztoy/index.html b/_figures/beztoy/index.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<head>
+<style>
+        svg {
+            touch-action: pinch-zoom;
+        }
+        svg circle {
+            pointer-events: all;
+        }
+</style>
+</head>
+<body>
+    <p>See <a href="https://github.com/raphlinus/raphlinus.github.io/pull/100">raphlinus#100</a> for more context.</p>
+</body>
diff --git a/_figures/beztoy/src/arc.rs b/_figures/beztoy/src/arc.rs
@@ -0,0 +1,71 @@
+// Copyright 2023 the raphlinus.github.io Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//! Convert an Euler spiral to a series of arcs.
+
+use xilem_web::svg::kurbo::{SvgArc, Vec2};
+
+use crate::euler::EulerSeg;
+
+#[allow(unused)]
+pub fn euler_to_arcs(es: &EulerSeg, tol: f64) -> Vec<SvgArc> {
+    let arclen = es.p0.distance(es.p1) / es.params.ch;
+    let n_subdiv = ((1. / 120.) * arclen / tol * es.params.k1.abs()).cbrt();
+    web_sys::console::log_1(&format!("n_subdiv = {n_subdiv}").into());
+    let n = (n_subdiv.ceil() as usize).max(1);
+    let dt = 1.0 / n as f64;
+    let mut p0 = es.p0;
+    (0..n)
+        .map(|i| {
+            let t0 = i as f64 * dt;
+            let t1 = t0 + dt;
+            let p1 = if i + 1 == n { es.p1 } else { es.eval(t1) };
+            let t = t0 + 0.5 * dt - 0.5;
+            let k = es.params.k0 + t * es.params.k1;
+            web_sys::console::log_1(&format!("{i}: k = {k} t = {t}").into());
+            let r = arclen / k;
+            let arc = SvgArc {
+                from: p0,
+                to: p1,
+                radii: Vec2::new(r, r),
+                x_rotation: 0.0,
+                large_arc: false,
+                sweep: k < 0.0,
+            };
+            p0 = p1;
+            arc
+        })
+        .collect()
+}
+
+pub fn espc_to_arcs(es: &EulerSeg, d: f64, tol: f64) -> Vec<SvgArc> {
+    let arclen = es.p0.distance(es.p1) / es.params.ch;
+    let est_err =
+        (1. / 120.) / tol * es.params.k1.abs() * (arclen + 0.4 * (es.params.k1 * d).abs());
+    let n_subdiv = est_err.cbrt();
+    web_sys::console::log_1(&format!("n_subdiv = {n_subdiv}").into());
+    let n = (n_subdiv.ceil() as usize).max(1);
+    let dt = 1.0 / n as f64;
+    let mut p0 = es.eval_with_offset(0.0, d);
+    (0..n)
+        .map(|i| {
+            let t0 = i as f64 * dt;
+            let t1 = t0 + dt;
+            let p1 = es.eval_with_offset(t1, d);
+            let t = t0 + 0.5 * dt - 0.5;
+            let k = es.params.k0 + t * es.params.k1;
+            let arclen_offset = arclen + d * k;
+            let r = arclen_offset / k;
+            let arc = SvgArc {
+                from: p0,
+                to: p1,
+                radii: Vec2::new(r, r),
+                x_rotation: 0.0,
+                large_arc: false,
+                sweep: k < 0.0,
+            };
+            p0 = p1;
+            arc
+        })
+        .collect()
+}