vecX: add truncate and midpoint functions. fixes #8 (#26)

* vecX: add truncate and midpoint functions

* who lints ya, baby?

Author: mreinstein

src/vec2-impl.ts

@@ -680,3 +680,32 @@ export function setLength(a: Vec2, len: number, dst?: Vec2) {
   normalize(a, dst);
   return mulScalar(dst, len, dst);
 }
+
+/**
+ * Ensure a vector is not longer than a max length
+ *
+ * @param a The vec2 to limit
+ * @param maxLen The longest length of the resulting vector
+ * @returns The vector, shortened to maxLen if it's too long
+ */
+export function truncate(a: Vec2, maxLen: number, dst?: Vec2) {
+  dst = dst || new VecType(2);
+
+  if (length(a) > maxLen) {
+    return setLength(a, maxLen, dst);
+  }
+
+  return copy(a, dst);
+}
+
+/**
+ * Return the vector exactly between 2 endpoint vectors
+ *
+ * @param a Endpoint 1
+ * @param b Endpoint 2
+ * @returns The vector exactly residing between endpoints 1 and 2
+ */
+export function midpoint(a: Vec2, b: Vec2, dst?: Vec2) {
+  dst = dst || new VecType(2);
+  return lerp(a, b, 0.5, dst);
+}

src/vec3-impl.ts

@@ -896,3 +896,32 @@ export function setLength(a: Vec3, len: number, dst?: Vec3) {
   normalize(a, dst);
   return mulScalar(dst, len, dst);
 }
+
+/**
+ * Ensure a vector is not longer than a max length
+ *
+ * @param a The vec3 to limit
+ * @param maxLen The longest length of the resulting vector
+ * @returns The vector, shortened to maxLen if it's too long
+ */
+export function truncate(a: Vec3, maxLen: number, dst?: Vec3) {
+  dst = dst || new VecType(3);
+
+  if (length(a) > maxLen) {
+    return setLength(a, maxLen, dst);
+  }
+
+  return copy(a, dst);
+}
+
+/**
+ * Return the vector exactly between 2 endpoint vectors
+ *
+ * @param a Endpoint 1
+ * @param b Endpoint 2
+ * @returns The vector exactly residing between endpoints 1 and 2
+ */
+export function midpoint(a: Vec3, b: Vec3, dst?: Vec3) {
+  dst = dst || new VecType(3);
+  return lerp(a, b, 0.5, dst);
+}

src/vec4-impl.ts

@@ -646,3 +646,32 @@ export function setLength(a: Vec4, len: number, dst?: Vec4) {
   normalize(a, dst);
   return mulScalar(dst, len, dst);
 }
+
+/**
+ * Ensure a vector is not longer than a max length
+ *
+ * @param a The vec4 to limit
+ * @param maxLen The longest length of the resulting vector
+ * @returns The vector, shortened to maxLen if it's too long
+ */
+export function truncate(a: Vec4, maxLen: number, dst?: Vec4) {
+  dst = dst || new VecType(4);
+
+  if (length(a) > maxLen) {
+    return setLength(a, maxLen, dst);
+  }
+
+  return copy(a, dst);
+}
+
+/**
+ * Return the vector exactly between 2 endpoint vectors
+ *
+ * @param a Endpoint 1
+ * @param b Endpoint 2
+ * @returns The vector exactly residing between endpoints 1 and 2
+ */
+export function midpoint(a: Vec4, b: Vec4, dst?: Vec4) {
+  dst = dst || new VecType(4);
+  return lerp(a, b, 0.5, dst);
+}

test/tests/vec2-test.js

@@ -510,5 +510,47 @@ describe('vec2', () => {
     });
   });
 
+  describe('truncate', function() {
+    describe('limit a vector to a max length', function() {
+      let vecA;
+
+      beforeEach(function () {
+        vecA = [10.323759005323593, 10.323759005323593];
+      });
+
+      it("should shorten the vector", function () {
+        const result = vec2.truncate(vecA, 4.0);
+        assertEqualApproximately(result, [2.82842712474619, 2.82842712474619]);
+        assertEqualApproximately(vec2.length(result), 4.0);
+      });
+
+      it("should preserve the vector when shorter than maxLen", function () {
+        const result = vec2.truncate(vecA, 18.0);
+        assertEqualApproximately(result, [10.323759005323593, 10.323759005323593]);
+        assertEqualApproximately(vec2.length(result), 14.6);
+      });
+    });
+  });
+
+  describe('midpoint', function() {
+    describe('return the midpoint between 2 vectors', function() {
+
+      it("should return the midpoint", function () {
+        const vecA = [ 0, 0 ]
+        const vecB = [ 10, 10 ]
+        const result = vec2.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 5, 5 ]);
+      });
+
+      it("should handle negatives", function () {
+        const vecA = [ -10, -10 ]
+        const vecB = [ 10, 10 ]
+        const result = vec2.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 0, 0 ]);
+      });
+
+    });
+  });
+
 });
 

test/tests/vec3-test.js

@@ -566,5 +566,47 @@ describe('vec3', () => {
     });
   });
 
+  describe('truncate', function() {
+    describe('limit a vector to a max length', function() {
+      let vecA;
+
+      beforeEach(function () {
+        vecA = [8.429313930168536, 8.429313930168536, 8.429313930168536];
+      });
+
+      it("should shorten the vector", function () {
+        const result = vec3.truncate(vecA, 4.0);
+        assertEqualApproximately(result, [2.309401076758503, 2.309401076758503, 2.309401076758503]);
+        assertEqualApproximately(vec3.length(result), 4.0);
+      });
+
+      it("should preserve the vector when shorter than maxLen", function () {
+        const result = vec3.truncate(vecA, 18.0);
+        assertEqualApproximately(result, [8.429313930168536, 8.429313930168536, 8.429313930168536]);
+        assertEqualApproximately(vec3.length(result), 14.6);
+      });
+    });
+  });
+
+  describe('midpoint', function() {
+    describe('return the midpoint between 2 vectors', function() {
+
+      it("should return the midpoint", function () {
+        const vecA = [ 0, 0, 0 ]
+        const vecB = [ 10, 10, 10 ]
+        const result = vec3.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 5, 5, 5 ]);
+      });
+
+      it("should handle negatives", function () {
+        const vecA = [ -10, -10, -10 ]
+        const vecB = [ 10, 10, 10 ]
+        const result = vec3.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 0, 0, 0 ]);
+      });
+
+    });
+  });
+
 });
 

test/tests/vec4-test.js

@@ -419,5 +419,47 @@ describe('vec4', () => {
     });
   });
 
+  describe('truncate', function() {
+    describe('limit a vector to a max length', function() {
+      let vecA;
+
+      beforeEach(function () {
+        vecA = [8.429313930168536, 8.429313930168536, 8.429313930168536, 8.429313930168536];
+      });
+
+      it("should shorten the vector", function () {
+        const result = vec4.truncate(vecA, 4.0);
+        assertEqualApproximately(result, [2, 2, 2, 2]);
+        assertEqualApproximately(vec4.length(result), 4.0);
+      });
+
+      it("should preserve the vector when shorter than maxLen", function () {
+        const result = vec4.truncate(vecA, 18.0);
+        assertEqualApproximately(result, [8.429313930168536, 8.429313930168536, 8.429313930168536, 8.429313930168536]);
+        assertEqualApproximately(vec4.length(result), 16.858627860337073);
+      });
+    });
+  });
+
+  describe('midpoint', function() {
+    describe('return the midpoint between 2 vectors', function() {
+
+      it("should return the midpoint", function () {
+        const vecA = [ 0, 0, 0, 0 ]
+        const vecB = [ 10, 10, 10, 10 ]
+        const result = vec4.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 5, 5, 5, 5 ]);
+      });
+
+      it("should handle negatives", function () {
+        const vecA = [ -10, -10, -10, -10 ]
+        const vecB = [ 10, 10, 10, 10 ]
+        const result = vec4.midpoint(vecA, vecB);
+        assertEqualApproximately(result, [ 0, 0, 0, 0 ]);
+      });
+
+    });
+  });
+
 });