Replace sqrt in Dimension by Fast inverse square root

src/Components/SVG/Elements/Dimension.tsx

@@ -1,5 +1,6 @@
 import * as React from 'react';
 import { NOTCHES_LENGTH } from '../../../utils/default';
+import { Qrsqrt } from '../../../utils/math';
 
 interface IDimensionProps {
   id: string
@@ -32,8 +33,8 @@ export const Dimension: React.FC<IDimensionProps> = (props: IDimensionProps) =>
   const [deltaX, deltaY] = [(props.xEnd - props.xStart), (props.yEnd - props.yStart)];
 
   // Get the unit vector
-  const norm = Math.sqrt(deltaX * deltaX + deltaY * deltaY);
+  const inv = Qrsqrt(deltaX * deltaX + deltaY * deltaY);
-  const [unitX, unitY] = [deltaX / norm, deltaY / norm];
+  const [unitX, unitY] = [deltaX * inv, deltaY * inv];
 
   // Get the perpandicular vector
   const [perpVecX, perpVecY] = [unitY, -unitX];

src/utils/math.ts

@@ -0,0 +1,21 @@
+const bytes = new ArrayBuffer(Float32Array.BYTES_PER_ELEMENT);
+const floatView = new Float32Array(bytes);
+const intView = new Uint32Array(bytes);
+const threehalfs = 1.5;
+
+/**
+ * Fast inverse square root
+ * http://en.wikipedia.org/wiki/Fast_inverse_square_root
+ * https://youtu.be/p8u_k2LIZyo
+ * @param number Number to square root
+ * @returns Approximation of the squqre root of the number
+ */
+export function Qrsqrt(number: number): number {
+  const x2 = number * 0.5;
+  floatView[0] = number;
+  intView[0] = 0x5f3759df - (intView[0] >> 1);
+  let y = floatView[0];
+  y = y * (threehalfs - (x2 * y * y));
+
+  return y;
+}