Updatable interpolators (#3)

smikhalevski · Feb 12, 2022 · 5e2b6ca · 5e2b6ca
1 parent 03bd9a7
commit 5e2b6ca
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Showing 5 changed files with 87 additions and 41 deletions.
diff --git a/src/main/cspline-monot.ts b/src/main/cspline-monot.ts
@@ -1,4 +1,4 @@
-import {MutableArrayLike} from './shared-types';
+import {Interpolator, MutableArrayLike} from './shared-types';
 import {binarySearch} from './binary-search';
 
 /**
@@ -19,18 +19,34 @@ import {binarySearch} from './binary-search';
  *
  * @see {@link https://en.wikipedia.org/wiki/Monotone_cubic_interpolation Monotone cubic interpolation}
  */
-export function csplineMonot(xs: ArrayLike<number>, ys: ArrayLike<number>): (x: number) => number {
-  const n = Math.min(xs.length, ys.length);
+export function csplineMonot(xs: ArrayLike<number>, ys: ArrayLike<number>): Interpolator {
+  let n = -1;
+  let splines: MutableArrayLike<number>;
 
-  if (n === 0) {
-    return () => NaN;
-  }
-  if (n === 1) {
-    const y0 = ys[0];
-    return () => y0;
-  }
-  const splines = createCSplinesMonot(xs, ys, n);
-  return (x) => interpolateCSplineMonot(xs, ys, x, n, splines);
+  const interp: Interpolator = (x) => {
+    if (n === 0) {
+      return NaN;
+    }
+    if (n === 1) {
+      return ys[0];
+    }
+    return interpolateCSplineMonot(xs, ys, x, n, splines);
+  };
+
+  interp.update = (nextXs, nextYs) => {
+    const nextN = Math.min(nextXs.length, nextYs.length);
+    xs = nextXs;
+    ys = nextYs;
+
+    if (nextN > 1) {
+      splines = createCSplinesMonot(xs, ys, nextN, n >= nextN ? splines : undefined);
+    }
+    n = nextN;
+  };
+
+  interp.update(xs, ys);
+
+  return interp;
 }
 
 const enum T {

diff --git a/src/main/cspline.ts b/src/main/cspline.ts
@@ -1,4 +1,4 @@
-import {MutableArrayLike} from './shared-types';
+import {Interpolator, MutableArrayLike} from './shared-types';
 import {binarySearch} from './binary-search';
 
 /**
@@ -16,18 +16,34 @@ import {binarySearch} from './binary-search';
  * @param ys The array of corresponding Y coordinates of pivot points.
  * @returns The function that takes X coordinate and returns an interpolated Y coordinate.
  */
-export function cspline(xs: ArrayLike<number>, ys: ArrayLike<number>): (x: number) => number {
-  const n = Math.min(xs.length, ys.length);
-
-  if (n === 0) {
-    return () => NaN;
-  }
-  if (n === 1) {
-    const y0 = ys[0];
-    return () => y0;
-  }
-  const splines = createCSplines(xs, ys, n);
-  return (x) => interpolateCSpline(xs, ys, x, n, splines);
+export function cspline(xs: ArrayLike<number>, ys: ArrayLike<number>): Interpolator {
+  let n = -1;
+  let splines: MutableArrayLike<number>;
+
+  const interp: Interpolator = (x) => {
+    if (n === 0) {
+      return NaN;
+    }
+    if (n === 1) {
+      return ys[0];
+    }
+    return interpolateCSpline(xs, ys, x, n, splines);
+  };
+
+  interp.update = (nextXs, nextYs) => {
+    const nextN = Math.min(nextXs.length, nextYs.length);
+    xs = nextXs;
+    ys = nextYs;
+
+    if (nextN > 1) {
+      splines = createCSplines(xs, ys, nextN, n >= nextN ? splines : undefined);
+    }
+    n = nextN;
+  };
+
+  interp.update(xs, ys);
+
+  return interp;
 }
 
 const enum T {

diff --git a/src/main/easing.ts b/src/main/easing.ts
@@ -3,8 +3,8 @@ import {exp, log} from './math-utils';
 /**
  * Maps `t` ∈ [0, 1] exponentially to [0, 1].
  *
- * @param t the value to map.
- * @param q greater values produce more bent curve, `f(t, 0) = t`.
+ * @param t The value to map.
+ * @param q Greater values produce more bent curve, `f(t, 0) = t`.
  */
 export function easeExp(t: number, q = 1): number {
   return q === 0 ? t : (exp(q * t) - 1) / (exp(q) - 1);
@@ -13,11 +13,11 @@ export function easeExp(t: number, q = 1): number {
 /**
  * Maps `t` ∈ [0, 1] logarithmically to [0, 1].
  *
- * @param x the value to map.
- * @param q greater values produce more bent curve, `f(t, 0) = t`.
+ * @param t The value to map.
+ * @param q Greater values produce more bent curve, `f(t, 0) = t`.
  */
-export function easeLog(x: number, q = 1): number {
-  return q === 0 ? x : log(x * (exp(q) - 1) + 1) / q;
+export function easeLog(t: number, q = 1): number {
+  return q === 0 ? t : log(t * (exp(q) - 1) + 1) / q;
 }
 
 export function easeInQuad(t: number): number {

diff --git a/src/main/lerp.ts b/src/main/lerp.ts
@@ -1,4 +1,5 @@
 import {binarySearch} from './binary-search';
+import {Interpolator} from './shared-types';
 
 /**
  * Returns a linear interpolation function for given pivot points.
@@ -15,17 +16,13 @@ import {binarySearch} from './binary-search';
  * @param ys The array of corresponding Y coordinates of pivot points.
  * @returns The function that takes X coordinate and returns an interpolated Y coordinate.
  */
-export function lerp(xs: ArrayLike<number>, ys: ArrayLike<number>): (x: number) => number {
-  const n = Math.min(xs.length, ys.length);
+export function lerp(xs: ArrayLike<number>, ys: ArrayLike<number>): Interpolator {
+  let n = -1;
 
-  if (n === 0) {
-    return () => NaN;
-  }
-  if (n === 1) {
-    const y0 = ys[0];
-    return () => y0;
-  }
-  return (x) => {
+  const interp: Interpolator = (x) => {
+    if (n === 0) {
+      return NaN;
+    }
     if (x <= xs[0]) {
       return ys[0];
     }
@@ -43,4 +40,14 @@ export function lerp(xs: ArrayLike<number>, ys: ArrayLike<number>): (x: number)
 
     return yj + (x - xj) / (xs[i] - xj) * (ys[i] - yj);
   };
+
+  interp.update = (nextXs, nextYs) => {
+    n = Math.min(nextXs.length, nextYs.length);
+    xs = nextXs;
+    ys = nextYs;
+  };
+
+  interp.update(xs, ys);
+
+  return interp;
 }
diff --git a/src/main/shared-types.ts b/src/main/shared-types.ts
@@ -1,4 +1,11 @@
+export interface Interpolator {
+  (x: number): number;
+
+  update(xs: ArrayLike<number>, ys: ArrayLike<number>): void;
+}
+
 export interface MutableArrayLike<T> {
   length: number;
+
   [n: number]: T;
 }