From 460a8d6d963fb77213c954d740064e431c106b69 Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Fri, 10 Oct 2025 22:37:01 +0300
Subject: [PATCH 1/6] Float64Buffer Matrices

---
 packages/engine/Source/Core/Matrix3.js    |  52 +++---
 packages/engine/Source/Core/Matrix4.js    | 187 ++++++++++------------
 packages/engine/Specs/Core/Matrix3Spec.js |   6 +-
 packages/engine/Specs/Core/Matrix4Spec.js |   6 +-
 4 files changed, 115 insertions(+), 136 deletions(-)

diff --git a/packages/engine/Source/Core/Matrix3.js b/packages/engine/Source/Core/Matrix3.js
index 7a7ab6c3213e..7887f3c53ba3 100644
--- a/packages/engine/Source/Core/Matrix3.js
+++ b/packages/engine/Source/Core/Matrix3.js
@@ -35,28 +35,30 @@ import CesiumMath from "./Math.js";
  * @see Matrix2
  * @see Matrix4
  */
-function Matrix3(
-  column0Row0,
-  column1Row0,
-  column2Row0,
-  column0Row1,
-  column1Row1,
-  column2Row1,
-  column0Row2,
-  column1Row2,
-  column2Row2,
-) {
-  this[0] = column0Row0 ?? 0.0;
-  this[1] = column0Row1 ?? 0.0;
-  this[2] = column0Row2 ?? 0.0;
-  this[3] = column1Row0 ?? 0.0;
-  this[4] = column1Row1 ?? 0.0;
-  this[5] = column1Row2 ?? 0.0;
-  this[6] = column2Row0 ?? 0.0;
-  this[7] = column2Row1 ?? 0.0;
-  this[8] = column2Row2 ?? 0.0;
+class Matrix3 extends Float64Array {
+  constructor(
+    column0Row0,
+    column1Row0,
+    column2Row0,
+    column0Row1,
+    column1Row1,
+    column2Row1,
+    column0Row2,
+    column1Row2,
+    column2Row2,
+  ) {
+    super(9);
+    this[0] = column0Row0 ?? 0.0;
+    this[1] = column0Row1 ?? 0.0;
+    this[2] = column0Row2 ?? 0.0;
+    this[3] = column1Row0 ?? 0.0;
+    this[4] = column1Row1 ?? 0.0;
+    this[5] = column1Row2 ?? 0.0;
+    this[6] = column2Row0 ?? 0.0;
+    this[7] = column2Row1 ?? 0.0;
+    this[8] = column2Row2 ?? 0.0;
+  }
 }
-
 /**
  * The number of elements used to pack the object into an array.
  * @type {number}
@@ -1671,9 +1673,7 @@ Matrix3.equalsEpsilon = function (left, right, epsilon) {
  * @type {Matrix3}
  * @constant
  */
-Matrix3.IDENTITY = Object.freeze(
-  new Matrix3(1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0),
-);
+Matrix3.IDENTITY = new Matrix3(1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0);
 
 /**
  * An immutable Matrix3 instance initialized to the zero matrix.
@@ -1681,9 +1681,7 @@ Matrix3.IDENTITY = Object.freeze(
  * @type {Matrix3}
  * @constant
  */
-Matrix3.ZERO = Object.freeze(
-  new Matrix3(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0),
-);
+Matrix3.ZERO = new Matrix3(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
 
 /**
  * The index into Matrix3 for column 0, row 0.
diff --git a/packages/engine/Source/Core/Matrix4.js b/packages/engine/Source/Core/Matrix4.js
index f30b8a733905..80e0afeea836 100644
--- a/packages/engine/Source/Core/Matrix4.js
+++ b/packages/engine/Source/Core/Matrix4.js
@@ -53,40 +53,43 @@ import RuntimeError from "./RuntimeError.js";
  * @see Matrix3
  * @see Packable
  */
-function Matrix4(
-  column0Row0,
-  column1Row0,
-  column2Row0,
-  column3Row0,
-  column0Row1,
-  column1Row1,
-  column2Row1,
-  column3Row1,
-  column0Row2,
-  column1Row2,
-  column2Row2,
-  column3Row2,
-  column0Row3,
-  column1Row3,
-  column2Row3,
-  column3Row3,
-) {
-  this[0] = column0Row0 ?? 0.0;
-  this[1] = column0Row1 ?? 0.0;
-  this[2] = column0Row2 ?? 0.0;
-  this[3] = column0Row3 ?? 0.0;
-  this[4] = column1Row0 ?? 0.0;
-  this[5] = column1Row1 ?? 0.0;
-  this[6] = column1Row2 ?? 0.0;
-  this[7] = column1Row3 ?? 0.0;
-  this[8] = column2Row0 ?? 0.0;
-  this[9] = column2Row1 ?? 0.0;
-  this[10] = column2Row2 ?? 0.0;
-  this[11] = column2Row3 ?? 0.0;
-  this[12] = column3Row0 ?? 0.0;
-  this[13] = column3Row1 ?? 0.0;
-  this[14] = column3Row2 ?? 0.0;
-  this[15] = column3Row3 ?? 0.0;
+class Matrix4 extends Float64Array {
+  constructor(
+    column0Row0,
+    column1Row0,
+    column2Row0,
+    column3Row0,
+    column0Row1,
+    column1Row1,
+    column2Row1,
+    column3Row1,
+    column0Row2,
+    column1Row2,
+    column2Row2,
+    column3Row2,
+    column0Row3,
+    column1Row3,
+    column2Row3,
+    column3Row3,
+  ) {
+    super(16);
+    this[0] = column0Row0 ?? 0.0;
+    this[1] = column0Row1 ?? 0.0;
+    this[2] = column0Row2 ?? 0.0;
+    this[3] = column0Row3 ?? 0.0;
+    this[4] = column1Row0 ?? 0.0;
+    this[5] = column1Row1 ?? 0.0;
+    this[6] = column1Row2 ?? 0.0;
+    this[7] = column1Row3 ?? 0.0;
+    this[8] = column2Row0 ?? 0.0;
+    this[9] = column2Row1 ?? 0.0;
+    this[10] = column2Row2 ?? 0.0;
+    this[11] = column2Row3 ?? 0.0;
+    this[12] = column3Row0 ?? 0.0;
+    this[13] = column3Row1 ?? 0.0;
+    this[14] = column3Row2 ?? 0.0;
+    this[15] = column3Row3 ?? 0.0;
+  }
 }
 
 /**
@@ -1929,41 +1932,23 @@ Matrix4.multiplyTransformation = function (left, right, result) {
   const right13 = right[13];
   const right14 = right[14];
 
-  const column0Row0 = left0 * right0 + left4 * right1 + left8 * right2;
-  const column0Row1 = left1 * right0 + left5 * right1 + left9 * right2;
-  const column0Row2 = left2 * right0 + left6 * right1 + left10 * right2;
-
-  const column1Row0 = left0 * right4 + left4 * right5 + left8 * right6;
-  const column1Row1 = left1 * right4 + left5 * right5 + left9 * right6;
-  const column1Row2 = left2 * right4 + left6 * right5 + left10 * right6;
-
-  const column2Row0 = left0 * right8 + left4 * right9 + left8 * right10;
-  const column2Row1 = left1 * right8 + left5 * right9 + left9 * right10;
-  const column2Row2 = left2 * right8 + left6 * right9 + left10 * right10;
-
-  const column3Row0 =
-    left0 * right12 + left4 * right13 + left8 * right14 + left12;
-  const column3Row1 =
-    left1 * right12 + left5 * right13 + left9 * right14 + left13;
-  const column3Row2 =
-    left2 * right12 + left6 * right13 + left10 * right14 + left14;
-
-  result[0] = column0Row0;
-  result[1] = column0Row1;
-  result[2] = column0Row2;
+  result[0] = left0 * right0 + left4 * right1 + left8 * right2;
+  result[1] = left1 * right0 + left5 * right1 + left9 * right2;
+  result[2] = left2 * right0 + left6 * right1 + left10 * right2;
   result[3] = 0.0;
-  result[4] = column1Row0;
-  result[5] = column1Row1;
-  result[6] = column1Row2;
+  result[4] = left0 * right4 + left4 * right5 + left8 * right6;
+  result[5] = left1 * right4 + left5 * right5 + left9 * right6;
+  result[6] = left2 * right4 + left6 * right5 + left10 * right6;
   result[7] = 0.0;
-  result[8] = column2Row0;
-  result[9] = column2Row1;
-  result[10] = column2Row2;
+  result[8] = left0 * right8 + left4 * right9 + left8 * right10;
+  result[9] = left1 * right8 + left5 * right9 + left9 * right10;
+  result[10] = left2 * right8 + left6 * right9 + left10 * right10;
   result[11] = 0.0;
-  result[12] = column3Row0;
-  result[13] = column3Row1;
-  result[14] = column3Row2;
+  result[12] = left0 * right12 + left4 * right13 + left8 * right14 + left12;
+  result[13] = left1 * right12 + left5 * right13 + left9 * right14 + left13;
+  result[14] = left2 * right12 + left6 * right13 + left10 * right14 + left14;
   result[15] = 1.0;
+
   return result;
 };
 
@@ -2968,25 +2953,23 @@ Matrix4.inverseTranspose = function (matrix, result) {
  * @type {Matrix4}
  * @constant
  */
-Matrix4.IDENTITY = Object.freeze(
-  new Matrix4(
-    1.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    1.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    1.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    1.0,
-  ),
+Matrix4.IDENTITY = new Matrix4(
+  1.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  1.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  1.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  1.0,
 );
 
 /**
@@ -2995,25 +2978,23 @@ Matrix4.IDENTITY = Object.freeze(
  * @type {Matrix4}
  * @constant
  */
-Matrix4.ZERO = Object.freeze(
-  new Matrix4(
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-    0.0,
-  ),
+Matrix4.ZERO = new Matrix4(
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
+  0.0,
 );
 
 /**
diff --git a/packages/engine/Specs/Core/Matrix3Spec.js b/packages/engine/Specs/Core/Matrix3Spec.js
index 3d2f4641aeb7..61aeb35c4cb0 100644
--- a/packages/engine/Specs/Core/Matrix3Spec.js
+++ b/packages/engine/Specs/Core/Matrix3Spec.js
@@ -358,7 +358,7 @@ describe("Core/Matrix3", function () {
 
   it("fromRotationX works without a result parameter", function () {
     const matrix = Matrix3.fromRotationX(0.0);
-    expect(matrix).toEqual(Matrix3.IDENTITY);
+    expect(Matrix3.equals(matrix, Matrix3.IDENTITY)).toBe(true);
   });
 
   it("fromRotationX works with a result parameter", function () {
@@ -371,7 +371,7 @@ describe("Core/Matrix3", function () {
 
   it("fromRotationY works without a result parameter", function () {
     const matrix = Matrix3.fromRotationY(0.0);
-    expect(matrix).toEqual(Matrix3.IDENTITY);
+    expect(Matrix3.equals(matrix, Matrix3.IDENTITY)).toBe(true);
   });
 
   it("fromRotationY works with a result parameter", function () {
@@ -384,7 +384,7 @@ describe("Core/Matrix3", function () {
 
   it("fromRotationZ works without a result parameter", function () {
     const matrix = Matrix3.fromRotationZ(0.0);
-    expect(matrix).toEqual(Matrix3.IDENTITY);
+    expect(Matrix3.equals(matrix, Matrix3.IDENTITY)).toBe(true);
   });
 
   it("fromRotationZ works with a result parameter", function () {
diff --git a/packages/engine/Specs/Core/Matrix4Spec.js b/packages/engine/Specs/Core/Matrix4Spec.js
index 375416d0a849..439d9ec78f86 100644
--- a/packages/engine/Specs/Core/Matrix4Spec.js
+++ b/packages/engine/Specs/Core/Matrix4Spec.js
@@ -727,7 +727,7 @@ describe("Core/Matrix4", function () {
       direction: Cartesian3.negate(Cartesian3.UNIT_Z, new Cartesian3()),
       up: Cartesian3.UNIT_Y,
     });
-    expect(expected).toEqual(returnedResult);
+    expect(Matrix4.equals(expected, returnedResult)).toBe(true);
   });
 
   it("fromCamera works with a result parameter", function () {
@@ -742,7 +742,7 @@ describe("Core/Matrix4", function () {
       result,
     );
     expect(returnedResult).toBe(result);
-    expect(returnedResult).toEqual(expected);
+    expect(Matrix4.equals(expected, returnedResult)).toBe(true);
   });
 
   it("computeOrthographicOffCenter works", function () {
@@ -1392,7 +1392,7 @@ describe("Core/Matrix4", function () {
 
   it("setRotation works", function () {
     const scaleVec = new Cartesian3(2.0, 3.0, 4.0);
-    const scale = Matrix4.fromScale(scaleVec, new Matrix3());
+    const scale = Matrix4.fromScale(scaleVec, new Matrix4());
     const rotation = Matrix3.fromRotationX(0.5, new Matrix3());
     const scaleRotation = Matrix4.setRotation(scale, rotation, new Matrix4());
 

From 7dd0a5ac46c28b350bf8544998fe0556c631b686 Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Fri, 10 Oct 2025 22:58:25 +0300
Subject: [PATCH 2/6] Fix failing tests

---
 packages/engine/Specs/Scene/CameraSpec.js                  | 2 +-
 packages/engine/Specs/Scene/GltfLoaderUtilSpec.js          | 4 +++-
 packages/engine/Specs/Scene/PropertyTexturePropertySpec.js | 4 +++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/packages/engine/Specs/Scene/CameraSpec.js b/packages/engine/Specs/Scene/CameraSpec.js
index 6cda5632cd20..dda1db7ce6a4 100644
--- a/packages/engine/Specs/Scene/CameraSpec.js
+++ b/packages/engine/Specs/Scene/CameraSpec.js
@@ -130,7 +130,7 @@ describe("Scene/Camera", function () {
       1.0,
     );
     const expected = Matrix4.multiply(rotation, translation, new Matrix4());
-    expect(viewMatrix).toEqual(expected);
+    expect(Matrix4.equals(viewMatrix, expected)).toBe(true);
   });
 
   it("get inverse view matrix", function () {
diff --git a/packages/engine/Specs/Scene/GltfLoaderUtilSpec.js b/packages/engine/Specs/Scene/GltfLoaderUtilSpec.js
index bef2cf665012..235def55ddcd 100644
--- a/packages/engine/Specs/Scene/GltfLoaderUtilSpec.js
+++ b/packages/engine/Specs/Scene/GltfLoaderUtilSpec.js
@@ -328,7 +328,9 @@ describe(
       });
 
       expect(modelTexture.texCoord).toBe(1);
-      expect(modelTexture.transform).toEqual(expectedTransform);
+      expect(Matrix3.equals(modelTexture.transform, expectedTransform)).toBe(
+        true,
+      );
     });
 
     it("createModelTextureReader handles KHR_texture_transform rotation correctly", function () {
diff --git a/packages/engine/Specs/Scene/PropertyTexturePropertySpec.js b/packages/engine/Specs/Scene/PropertyTexturePropertySpec.js
index 0bdb4bc5bea5..db6cc8d0c7fa 100644
--- a/packages/engine/Specs/Scene/PropertyTexturePropertySpec.js
+++ b/packages/engine/Specs/Scene/PropertyTexturePropertySpec.js
@@ -109,7 +109,9 @@ describe(
       const modelTextureReader = propertyTextureProperty.textureReader;
       expect(modelTextureReader.texture).toBe(texture);
       expect(modelTextureReader.texCoord).toBe(1);
-      expect(modelTextureReader.transform).toEqual(expectedTransform);
+      expect(
+        Matrix3.equals(modelTextureReader.transform, expectedTransform),
+      ).toBe(true);
       expect(modelTextureReader.channels).toBe("rgb");
     });
 

From 6a759d3b9f9db13f05978ad72a4495f312c093f4 Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Fri, 10 Oct 2025 23:08:18 +0300
Subject: [PATCH 3/6] Add changelog

---
 CHANGES.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGES.md b/CHANGES.md
index 23f5e58cbf33..497d34fef2ba 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -9,6 +9,10 @@
 - `scene.drillPick` now uses a breadth-first search strategy instead of depth-first. This may change which entities are picked when
   using large values of `width` and `height` when providing a `limit`, prioritizing entities closer to the camera.
 
+#### Additions :tada:
+
+- Matrices are now backed by `Float64Array`'s, making operations up to 2x faster, resulting in performance improvements across the board. [#12973](https://github.com/CesiumGS/cesium/pull/12973)
+
 #### Fixes :wrench:
 
 - Fixes an event bug following recent changes, where adding a new listener during an event callback caused an infinite loop. [#12955](https://github.com/CesiumGS/cesium/pull/12955)

From 7c80345833d32461ba0106cdd4814287c7c8c304 Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Sun, 12 Oct 2025 01:00:28 +0300
Subject: [PATCH 4/6] Options for Frozen Matrices

---
 packages/engine/Source/Core/Matrix3.js      |  38 +++--
 packages/engine/Source/Core/Matrix4.js      | 158 +++++++++++++-------
 packages/engine/Source/Core/freezeMatrix.js |  88 +++++++++++
 3 files changed, 218 insertions(+), 66 deletions(-)
 create mode 100644 packages/engine/Source/Core/freezeMatrix.js

diff --git a/packages/engine/Source/Core/Matrix3.js b/packages/engine/Source/Core/Matrix3.js
index 7887f3c53ba3..0a066385be75 100644
--- a/packages/engine/Source/Core/Matrix3.js
+++ b/packages/engine/Source/Core/Matrix3.js
@@ -2,6 +2,7 @@ import Cartesian3 from "./Cartesian3.js";
 import Check from "./Check.js";
 import defined from "./defined.js";
 import DeveloperError from "./DeveloperError.js";
+import freezeMatrix from "./freezeMatrix.js";
 import CesiumMath from "./Math.js";
 
 /**
@@ -1667,22 +1668,6 @@ Matrix3.equalsEpsilon = function (left, right, epsilon) {
   );
 };
 
-/**
- * An immutable Matrix3 instance initialized to the identity matrix.
- *
- * @type {Matrix3}
- * @constant
- */
-Matrix3.IDENTITY = new Matrix3(1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0);
-
-/**
- * An immutable Matrix3 instance initialized to the zero matrix.
- *
- * @type {Matrix3}
- * @constant
- */
-Matrix3.ZERO = new Matrix3(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
-
 /**
  * The index into Matrix3 for column 0, row 0.
  *
@@ -1833,4 +1818,25 @@ Matrix3.prototype.toString = function () {
     `(${this[2]}, ${this[5]}, ${this[8]})`
   );
 };
+
+/**
+ * An immutable Matrix3 instance initialized to the identity matrix.
+ *
+ * @type {Readonly<Matrix3>}
+ * @constant
+ */
+Matrix3.IDENTITY = freezeMatrix(
+  new Matrix3(1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0),
+);
+
+/**
+ * An immutable Matrix3 instance initialized to the zero matrix.
+ *
+ * @type {Readonly<Matrix3>}
+ * @constant
+ */
+Matrix3.ZERO = freezeMatrix(
+  new Matrix3(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0),
+);
+
 export default Matrix3;
diff --git a/packages/engine/Source/Core/Matrix4.js b/packages/engine/Source/Core/Matrix4.js
index 80e0afeea836..9d67d9a61124 100644
--- a/packages/engine/Source/Core/Matrix4.js
+++ b/packages/engine/Source/Core/Matrix4.js
@@ -7,6 +7,7 @@ import DeveloperError from "./DeveloperError.js";
 import CesiumMath from "./Math.js";
 import Matrix3 from "./Matrix3.js";
 import RuntimeError from "./RuntimeError.js";
+import freezeMatrix from "./freezeMatrix.js";
 
 /**
  * A 4x4 matrix, indexable as a column-major order array.
@@ -2947,56 +2948,6 @@ Matrix4.inverseTranspose = function (matrix, result) {
   );
 };
 
-/**
- * An immutable Matrix4 instance initialized to the identity matrix.
- *
- * @type {Matrix4}
- * @constant
- */
-Matrix4.IDENTITY = new Matrix4(
-  1.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  1.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  1.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  1.0,
-);
-
-/**
- * An immutable Matrix4 instance initialized to the zero matrix.
- *
- * @type {Matrix4}
- * @constant
- */
-Matrix4.ZERO = new Matrix4(
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-  0.0,
-);
-
 /**
  * The index into Matrix4 for column 0, row 0.
  *
@@ -3211,4 +3162,111 @@ Matrix4.prototype.toString = function () {
     `(${this[3]}, ${this[7]}, ${this[11]}, ${this[15]})`
   );
 };
+
+// Frozen Matrix option 1: Only implement the interface as generated by Cesium.d.ts (meaning, without exposing any Float64Array methods)
+/**
+ * @returns {Readonly<Matrix4>} a frozen matrix
+ */
+// eslint-disable-next-line no-unused-vars
+function makeFrozenMatrix4(
+  column0Row0,
+  column1Row0,
+  column2Row0,
+  column3Row0,
+  column0Row1,
+  column1Row1,
+  column2Row1,
+  column3Row1,
+  column0Row2,
+  column1Row2,
+  column2Row2,
+  column3Row2,
+  column0Row3,
+  column1Row3,
+  column2Row3,
+  column3Row3,
+) {
+  /** @type {Matrix4} */
+  const matrix = {
+    [0]: column0Row0 ?? 0.0,
+    [1]: column0Row1 ?? 0.0,
+    [2]: column0Row2 ?? 0.0,
+    [3]: column0Row3 ?? 0.0,
+    [4]: column1Row0 ?? 0.0,
+    [5]: column1Row1 ?? 0.0,
+    [6]: column1Row2 ?? 0.0,
+    [7]: column1Row3 ?? 0.0,
+    [8]: column2Row0 ?? 0.0,
+    [9]: column2Row1 ?? 0.0,
+    [10]: column2Row2 ?? 0.0,
+    [11]: column2Row3 ?? 0.0,
+    [12]: column3Row0 ?? 0.0,
+    [13]: column3Row1 ?? 0.0,
+    [14]: column3Row2 ?? 0.0,
+    [15]: column3Row3 ?? 0.0,
+    length: Matrix4.packedLength,
+  };
+
+  matrix.clone = Matrix4.prototype.clone.bind(matrix);
+  matrix.equals = Matrix4.prototype.equals.bind(matrix);
+  matrix.equalsEpsilon = Matrix4.prototype.equalsEpsilon.bind(matrix);
+  matrix.toString = Matrix4.prototype.toString.bind(matrix);
+
+  return Object.freeze(matrix);
+}
+
+/**
+ * An immutable Matrix4 instance initialized to the identity matrix.
+ *
+ * @type {Readonly<Matrix4>}
+ * @constant
+ */
+Matrix4.IDENTITY = freezeMatrix(
+  new Matrix4(
+    1.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    1.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    1.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    1.0,
+  ),
+);
+
+/**
+ * An immutable Matrix4 instance initialized to the zero matrix.
+ *
+ * @type {Readonly<Matrix4>}
+ * @constant
+ */
+Matrix4.ZERO = freezeMatrix(
+  new Matrix4(
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+    0.0,
+  ),
+);
+
 export default Matrix4;
diff --git a/packages/engine/Source/Core/freezeMatrix.js b/packages/engine/Source/Core/freezeMatrix.js
new file mode 100644
index 000000000000..069e2534ffa5
--- /dev/null
+++ b/packages/engine/Source/Core/freezeMatrix.js
@@ -0,0 +1,88 @@
+import DeveloperError from "./DeveloperError";
+
+// Deep copies all property descriptors of the provided object.
+function getPropertyDescriptorMap(object) {
+  /** @type {PropertyDescriptorMap} */
+  const propertyDescriptorMap = {};
+  let current = object;
+
+  while (current) {
+    Object.entries(Object.getOwnPropertyDescriptors(current)).forEach(
+      ([name, descriptor]) => {
+        if (propertyDescriptorMap[name]) {
+          return;
+        }
+        propertyDescriptorMap[name] = descriptor;
+      },
+    );
+    Object.getOwnPropertySymbols(current).forEach(
+      // eslint-disable-next-line no-loop-func
+      (symbol) => {
+        if (propertyDescriptorMap[symbol]) {
+          return;
+        }
+        propertyDescriptorMap[symbol] = {
+          value: object[symbol],
+          enumerable: false,
+        };
+      },
+    );
+
+    // Move up the prototype chain
+    current = Object.getPrototypeOf(current);
+    if (current.constructor.name === "Object") {
+      break;
+    }
+  }
+
+  return propertyDescriptorMap;
+}
+
+// Frozen Matrix option 2: Generate a true Matrix4, including all underlying Float64Array methods.
+// This has 100% parity with a regular Matrix4, with the exception that calling any methods that change the underlying matrix,
+// or accessing the buffer will throw a DeveloperError
+/**
+ * @template T
+ * @param {T} matrix
+ * @returns {Readonly<T>} a frozen matrix
+ */
+export default function freezeMatrix(matrix) {
+  const properties = getPropertyDescriptorMap(matrix);
+  // Get both regular and symbol keys
+  for (const property of Reflect.ownKeys(properties)) {
+    const descriptor = properties[property];
+    // These methods manipulate directly or allow the manipulation of the underlying buffer. Make them illegal.
+    if (
+      ["copyWithin", "fill", "reverse", "set", "sort", "subarray"].includes(
+        property,
+      )
+    ) {
+      descriptor.value = function () {
+        throw new DeveloperError(`Cannot call ${property} on a frozen Matrix`);
+      };
+    } else if (typeof descriptor.value === "function") {
+      // Proxy all functions back onto the original matrix
+      descriptor.value = descriptor.value.bind(matrix);
+    }
+    // Deny access the underlying buffer on the facade
+    if (property === "buffer") {
+      descriptor.get = function () {
+        throw new DeveloperError(`Cannot access buffer of a frozen Matrix`);
+      };
+      delete descriptor.value;
+    }
+  }
+  properties.toString = {
+    value: matrix.toString,
+  };
+  properties.constructor = {
+    value: matrix.constructor,
+  };
+
+  // Create a fake matrix object and map all properties of the real matrix onto it
+  const fakeMatrix = Object.create(Object, properties);
+
+  // Freeze the fake matrix object. We know have a fully compatible Matrix clone which is still backed
+  // by an underlying Float64Array, but is completed frozen to external changes.
+  return Object.freeze(fakeMatrix);
+}

From 3075077452e69c60f843f2b03952c8ca09fc2e5f Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Sun, 12 Oct 2025 01:08:07 +0300
Subject: [PATCH 5/6] Fix build error

---
 packages/engine/Source/Core/freezeMatrix.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/engine/Source/Core/freezeMatrix.js b/packages/engine/Source/Core/freezeMatrix.js
index 069e2534ffa5..a1b66a28d4ed 100644
--- a/packages/engine/Source/Core/freezeMatrix.js
+++ b/packages/engine/Source/Core/freezeMatrix.js
@@ -1,4 +1,4 @@
-import DeveloperError from "./DeveloperError";
+import DeveloperError from "./DeveloperError.js";
 
 // Deep copies all property descriptors of the provided object.
 function getPropertyDescriptorMap(object) {

From 28286e9e28f512b38eeabca3adc79288872d130f Mon Sep 17 00:00:00 2001
From: Adam Beili <adam.v.beili@gmail.com>
Date: Thu, 13 Nov 2025 19:33:03 +0100
Subject: [PATCH 6/6] Update changes

---
 CHANGES.md                                  |  5 +----
 packages/engine/Source/Core/freezeMatrix.js | 21 +++++++++------------
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index c4fc015da67d..d6262e226ec3 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -11,6 +11,7 @@
 #### Additions :tada:
 
 - Added `scene.pickAsync` for non GPU blocking picking using WebGL2 [#12983](https://github.com/CesiumGS/cesium/pull/12983)
+- Speed up `MatrixN` operations, improving performance when picking terrain and 3D tiles. [#12973](https://github.com/CesiumGS/cesium/pull/12973)
 
 ## 1.135 - 2025-11-03
 
@@ -26,10 +27,6 @@
 - Added experimental support for loading 3D Tiles as terrain, via `Cesium3DTilesTerrainProvider`. See [the PR](https://github.com/CesiumGS/cesium/pull/12963) for limitations on the types of 3D Tiles that can be used. [#12296](https://github.com/CesiumGS/cesium/issues/12296)
 - Added support for [EXT_mesh_primitive_edge_visibility](https://github.com/KhronosGroup/glTF/pull/2479) glTF extension. [#12765](https://github.com/CesiumGS/cesium/issues/12765)
 
-#### Additions :tada:
-
-- Matrices are now backed by `Float64Array`'s, making operations up to 2x faster, resulting in performance improvements across the board. [#12973](https://github.com/CesiumGS/cesium/pull/12973)
-
 #### Fixes :wrench:
 
 - Improved performance of `scene.drillPick`. [#12916](https://github.com/CesiumGS/cesium/pull/12916)
diff --git a/packages/engine/Source/Core/freezeMatrix.js b/packages/engine/Source/Core/freezeMatrix.js
index a1b66a28d4ed..27b199e60dea 100644
--- a/packages/engine/Source/Core/freezeMatrix.js
+++ b/packages/engine/Source/Core/freezeMatrix.js
@@ -15,18 +15,15 @@ function getPropertyDescriptorMap(object) {
         propertyDescriptorMap[name] = descriptor;
       },
     );
-    Object.getOwnPropertySymbols(current).forEach(
-      // eslint-disable-next-line no-loop-func
-      (symbol) => {
-        if (propertyDescriptorMap[symbol]) {
-          return;
-        }
-        propertyDescriptorMap[symbol] = {
-          value: object[symbol],
-          enumerable: false,
-        };
-      },
-    );
+    Object.getOwnPropertySymbols(current).forEach((symbol) => {
+      if (propertyDescriptorMap[symbol]) {
+        return;
+      }
+      propertyDescriptorMap[symbol] = {
+        value: object[symbol],
+        enumerable: false,
+      };
+    });
 
     // Move up the prototype chain
     current = Object.getPrototypeOf(current);