feat: Add traditional lerp functions for ease of use

CHANGELOG.md

@@ -75,6 +75,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Added
 
+- Added new `ex.lerp(...)`, `ex.inverseLerp(...)`, and `ex.remap(...)` for numbers
+- Added new `ex.lerpVector(...)`,` ex.inverseLerpVector(...)`, and `ex.remapVector(...)` for `ex.Vector`
 - Added new `actor.actions.flash(...)` `Action` to flash a color for a period of time
 - Added a new `ex.NineSlice` `Graphic` for creating arbitrarily resizable rectangular regions, useful for creating UI, backgrounds, and other resizable elements.
   ```typescript

src/engine/Math/Index.ts

@@ -10,3 +10,4 @@ export * from './line-segment';
 export * from './projection';
 export * from './ray';
 export * from './util';
+export * from './lerp';

src/engine/Math/lerp.ts

@@ -0,0 +1,79 @@
+import { Vector } from './vector';
+
+/**
+ * Linear interpolation between `a` and `b`, at `time = 0` the value will be `a` at `time = 1` the value will be `b`
+ * @param a
+ * @param b
+ * @param time
+ */
+export function lerp(a: number, b: number, time: number): number {
+  return (1 - time) * a + b * time;
+}
+
+/**
+ * Linear interpolation between `a` and `b`, at `time = 0` the value will be `a` at `time = 1` the value will be `b`
+ * @param a
+ * @param b
+ * @param time
+ */
+export function lerpVector(a: Vector, b: Vector, time: number): Vector {
+  return a.scale(1 - time).add(b.scale(time));
+}
+
+/**
+ * Inverse of a linear interpolation, given a `value` in between `a` and `b` return how close to `a` or `b` the `value` is.
+ *
+ * Example: `a=1`, `b=5`, `value=4` will return `.75`
+ * @param a
+ * @param b
+ * @param value
+ */
+export function inverseLerp(a: number, b: number, value: number): number {
+  return (value - a) / (b - a);
+}
+
+/**
+ * Inverse of a linear interpolation, given a `value` in between `a` and `b` return how close to `a` or `b` the `value` is.
+ *
+ * **Warning** assumes that the `value` vector is co-linear with vector `a` and `b`
+ *
+ * Example: `a=1`, `b=5`, `value=4` will return `.75`
+ * @param a
+ * @param b
+ * @param value
+ */
+export function inverseLerpVector(a: Vector, b: Vector, value: Vector): number {
+  const numerator = value.sub(a);
+  const denominator = b.sub(a);
+  const x = numerator.x / denominator.x;
+  const y = numerator.y / denominator.y;
+  return Math.min(x, y);
+}
+
+/**
+ * Remaps a value from a source domain to a destination
+ * @param minSource
+ * @param maxSource
+ * @param minDestination
+ * @param maxDestination
+ * @param value
+ */
+export function remap(minSource: number, maxSource: number, minDestination: number, maxDestination: number, value: number): number {
+  const time = inverseLerp(minSource, maxSource, value);
+  return lerp(minDestination, maxDestination, time);
+}
+
+/**
+ * Remaps a value from a source domain to a destination
+ *
+ * **Warning** assumes that the `value` vector is co-linear with vector `minSource` and `maxSource`
+ * @param minSource
+ * @param maxSource
+ * @param minDestination
+ * @param maxDestination
+ * @param value
+ */
+export function remapVector(minSource: Vector, maxSource: Vector, minDestination: Vector, maxDestination: Vector, value: Vector): Vector {
+  const time = inverseLerpVector(minSource, maxSource, value);
+  return lerpVector(minDestination, maxDestination, time);
+}