this rename is absolutely stupid

docs/chapters/pointvectors3d/vector-lib.js

@@ -0,0 +1,71 @@
+function normalize(v) {
+    let z = v.z || 0;
+    var d = Math.sqrt(v.x*v.x + v.y*v.y + z*z);
+    let r = { x:v.x/d, y:v.y/d };
+    if (v.z !== undefined) r.z = z/d;
+    return r;
+}
+
+function dot(v1, v2) {
+    let z1 = v1.z || 0;
+    let z2 = v2.z || 0;
+    return v1.x * v2.x + v1.y * v2.y + z1 * z2;
+}
+
+function scale(v, s) {
+    let r = {
+        x: s * v.x,
+        y: s * v.y
+    }
+    if (v.z !== undefined) {
+        r.z = s * v.z
+    }
+    return r;
+}
+
+function plus(v1, v2) {
+    let r = {
+        x: v1.x + v2.x,
+        y: v1.y + v2.y
+    };
+    if (v1.z !== undefined || v2.z !== undefined) {
+        r.z = (v1.z||0) + (v2.z||0);
+    };
+    return r;
+}
+
+function minus(v1, v2) {
+    let r = {
+        x: v1.x - v2.x,
+        y: v1.y - v2.y
+    };
+    if (v1.z !== undefined || v2.z !== undefined) {
+        r.z = (v1.z||0) - (v2.z||0);
+    };
+    return r;
+}
+
+function cross(v1, v2) {
+    if (v1.z === undefined || v2.z === undefined) {
+        throw new Error(`Cross product is not defined for 2D vectors.`);
+    }
+    return {
+        x: v1.y * v2.z - v1.z * v2.y,
+        y: v1.z * v2.x - v1.x * v2.z,
+        z: v1.x * v2.y - v1.y * v2.x
+    };
+}
+
+function lerp(t, v1, v2) {
+    let r = {
+        x: (1-t)*v1.x + t*v2.x,
+        y: (1-t)*v1.y + t*v2.y
+    };
+    if (v1.z !== undefined || v2.z !== undefined) {
+        r.z = (1-t)*(v1.z||0) + t*(v2.z||0);
+    };
+    return r;
+}
+
+
+export default { normalize, dot, scale, plus, minus, cross, lerp }