Fix Quaternion::Quaternion(Matrix3x3) with more correct algorithm.

README.md

@@ -10,7 +10,7 @@ J3ML is a "Modern C++" library designed to provide comprehensive support for 3D
 
 ## Features
 
-* <b>Vector Operations:</b> Comprehensive support for 3D vector operations including addition, subtraction, scalar multiplication, dot product, cross product, normalization, and more. 
+* **Vector Operations:** Comprehensive support for 3D vector operations including addition, subtraction, scalar multiplication, dot product, cross product, normalization, and more. 
 * **Matrix Operations:** Efficient implementation of 3x3 and 4x4 matrices with support for common operations such as multiplication, transpose, determinant calculation, and inverse calculation.
 * **Quaternion Operations:** Quaternion manipulation functions including conversion to/from axis-angle representation, quaternion multiplication, normalization, and interpolation (slerp).
 * **Transformation Functions:** Functions for transforming points, vectors, and normals using matrices and quaternions.
@@ -18,29 +18,68 @@ J3ML is a "Modern C++" library designed to provide comprehensive support for 3D
 * **Algorithms:** Implementation of various algorithms including Gilbert-Johnson-Keerthi (GJK) algorithm for collision detection, random number generator, and more.
 * **Utility Functions:** Additional utilities such as conversion between degrees and radians, random number generation, and common constants.
 
-# Usage
+## Coming Soon
 
-To use J3ML in your C++ project, simply include the necessary header files and link against the library. Here's a basic example of how to use the library to perform vector addition:
+* **SIMD:** (Single-instruction, multiple-data) utilizes a vectorized instruction set to compute operations on multiple values at once. This is particularly useful in matrix maths.
+* **LUTs:** Compute Lookup-tables for common operations, and bake them into your program via constexpr. (Sin, Cos, Tan, Sqrt, FastInverseSqrt)
 
+# Installation
+
+We support integration via CMake Package Manager (CPM). It's quite clean and flexible. It's a single CMake script too.
+
+Here's what we recommend:
+
+Install CPM.cmake to a `cmake` directory in your project root, and add the lines below into your CMakeLists.txt
+
+To integrate the package manager:
+```cmake
+include("cmake/CPM.cmake")
+```
+
+To automatically download and build J3ML version 3.4.5 (Check releases for new versions!):
+
+```cmake
+CPMAddPackage(
+        NAME J3ML
+        URL https::/git.redacted.cc/josh/J3ML/archive/3.4.5.zip
+)
+```
+Then you should be able to link J3ML to your project like any other library:
+
+```cmake
+target_include_directories(MyProgramOrLib PUBLIC ${J3ML_SOURCE_DIR}/include)
+###
+target_link_libraries(MyProgramOrLib PUBLIC J3ML)
+```
+
+
+# Usage Samples
+
+## 2D Vector Operations
 
 ```cpp
+#include <J3ML/LinearAlgebra.hpp>
 
-#include <iostream>
+Vector2 position {10.f, 10.f};
+Vector2 velocity {5.f, 1.5f};
+float step = 1.f/60.f;
+
+void doStep() {
+    position = position + (velocity * step);
+    velocity = velocity.Lerp(Vector2::Zero, step);
+    float speed = velocity.Length();
+}
+```
+
+## Matrix3x3 and Rotation Types
+
+```cpp
 #include <j3ml/LinearAlgebra.h>
 
-int main() {
-    // Create two 3D vectors
-    Vector3 v1(1.0, 2.0, 3.0);
-    Vector3 v2(4.0, 5.0, 6.0);
-
-    // Perform vector addition
-    Vector3 result = v1 + v2;
-    
-    // Output the result
-    std::cout << "Result: " << result << std::endl;
-    
-    return 0;
-}
+Matrix3x3 mRotation = Matrix3x3::RotateX(Math::PiOverTwo);
+Quaternion qRotation(mRotation); // Convert to Quaternion
+AxisAngle aRotation(qRotation); // Convert to AxisAngle
+EulerAngleXYZ eRotation(aRotation); // Convert to Euler Angle (XYZ)
 ```
 
 For more detailed usage instructions and examples, please refer to the documentation.

include/J3ML/LinearAlgebra.hpp

@@ -1,5 +1,5 @@
 //// Dawsh Linear Algebra Library - Everything you need for 3D math
-/// @file LinearAlgebra.h
+/// @file LinearAlgebra.hpp
 /// @description Includes all LinearAlgebra classes and functions
 /// @author Josh O'Leary, William Tomasine II
 /// @copyright 2024 Redacted Software
@@ -9,11 +9,6 @@
 
 #pragma once
 
-// TODO: Enforce Style Consistency (Function Names use MicroSoft Case)
-// TODO: Implement Templated Linear Algebra
-
-
-// Library Code //
 
 #include "J3ML/LinearAlgebra/Vector2.hpp"
 #include "J3ML/LinearAlgebra/Vector3.hpp"

src/J3ML/LinearAlgebra/Quaternion.cpp

@@ -16,7 +16,9 @@ namespace J3ML::LinearAlgebra {
     }
 
     Quaternion::Quaternion(const Matrix3x3& ro_mat) {
-        auto m = ro_mat.Transposed();
+        // https://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/
+
+        auto m = ro_mat;//.Transposed();
         auto m00 = m.At(0,0);
         auto m01 = m.At(0, 1);
         auto m02 = m.At(0, 2);
@@ -27,6 +29,38 @@ namespace J3ML::LinearAlgebra {
         auto m21 = m.At(2, 1);
         auto m22 = m.At(2, 2);
 
+        float tr = m00 + m11 + m22;
+
+        if (tr > 0) {
+            float S = Math::Sqrt(tr + 1.f) * 2; // S = 4*qw
+
+            w = 0.25f * S;
+            x = (m21 - m12) / S;
+            y = (m02 - m20) / S;
+            z = (m10 - m01) / S;
+        } else {
+            if (m00 > m11 && m00 > m22) {
+                float S = 2.f * Math::Sqrt(1.f + m00 - m11 - m22);
+                w = (m21 - m12) / S;
+                x = 0.25f * S;
+                y = (m01 + m10) / S;
+                z = (m02 + m20) / S;
+            } else if (m11 > m22) {
+                float s = 2.f * Math::Sqrt(1.f + m11 - m00 - m22);
+                w = (m02 - m20) / s;
+                x = (m01 + m10) / s;
+                y = 0.25f * s;
+                z = (m12 + m21) / s;
+            } else {
+                float s = 2.f * Math::Sqrt(1.f + m22 - m00 - m11);
+                w = (m10 - m01) / s;
+                x = (m02 + m20) / s;
+                y = (m12 + m21) / s;
+                z = 0.25f * s;
+            }
+        }
+
+        /*
         auto field_w = std::sqrt(1.f + m00 + m11 + m22) / 2.f;
         float w4 = (4.f * field_w);
 
@@ -38,6 +72,7 @@ namespace J3ML::LinearAlgebra {
         w = field_w;
         bool success = Normalize();
         // TODO: Validate normalization success.
+        */
     }
 
     Quaternion::Quaternion(const Matrix4x4& ro_mat) {