From 13ecebfa6f3a590d8c96458c69205afc828bb22f Mon Sep 17 00:00:00 2001
From: Matteo De Carlo <matteo.dek@gmail.com>
Date: Thu, 6 Nov 2025 23:05:45 +0100
Subject: [PATCH] Fix lookAt functions

-  to work with RowMajor (RowMajor vectors are a compilation error in Eigen)
- lookatRh had an extra `-`, fixed by flipping subtraction to define the vector `f`
---
 include/eigen_graphics/all.h | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/include/eigen_graphics/all.h b/include/eigen_graphics/all.h
index edb54c8..9f89f52 100644
--- a/include/eigen_graphics/all.h
+++ b/include/eigen_graphics/all.h
@@ -399,36 +399,36 @@ Eigen::Matrix<typename Derived::Scalar, 4, 4, Derived::Options> rotateLh(const E
 // BEGIN: view matrix creation functions
 // ----------------------------------------------------------------------------
 
-template <typename Derived>
-Eigen::Matrix<typename Derived::Scalar, 4, 4, Derived::Options> lookAtRh(const Eigen::MatrixBase<Derived>& eye,
-                                                                         const Eigen::MatrixBase<Derived>& target,
-                                                                         const Eigen::MatrixBase<Derived>& worldUp) {
+template <typename Derived, StorageOptions Options = StorageOptions::ColMajor>
+Eigen::Matrix<typename Derived::Scalar, 4, 4, Options> lookAtRh(const Eigen::MatrixBase<Derived>& eye,
+                                                                const Eigen::MatrixBase<Derived>& target,
+                                                                const Eigen::MatrixBase<Derived>& worldUp) {
   static_assert(Derived::RowsAtCompileTime == 3 && Derived::ColsAtCompileTime == 1, "lookAtRh requires 3x1 vectors.");
 
   using Scalar = typename Derived::Scalar;
-  using Vector3 = Eigen::Matrix<Scalar, 3, 1, Derived::Options>;
-  using Matrix4 = Eigen::Matrix<Scalar, 4, 4, Derived::Options>;
+  using Vector3 = Eigen::Matrix<Scalar, 3, 1, ::Eigen::ColMajor>;
+  using Matrix4 = Eigen::Matrix<Scalar, 4, 4, Options>;
 
-  Vector3 f = (target - eye).normalized();
+  Vector3 f = (eye - target).normalized();
   Vector3 r = worldUp.cross(f).normalized();
   Vector3 u = f.cross(r);
 
   Matrix4 viewMatrix;
 
-  if constexpr (Derived::Options == Eigen::RowMajor) {
+  if constexpr (Options == Eigen::RowMajor) {
     // clang-format off
     viewMatrix <<
-      r.x(),   u.x(),     -f.x(),  Scalar(0),
-      r.y(),   u.y(),     -f.y(),  Scalar(0),
-      r.z(),   u.z(),     -f.z(),  Scalar(0),
+      r.x(),   u.x(),     f.x(),  Scalar(0),
+      r.y(),   u.y(),     f.y(),  Scalar(0),
+      r.z(),   u.z(),     f.z(),  Scalar(0),
       -r.dot(eye),  -u.dot(eye),  -f.dot(eye),  Scalar(1);
     // clang-format on
-  } else if constexpr (Derived::Options == Eigen::ColMajor) {
+  } else if constexpr (Options == Eigen::ColMajor) {
     // clang-format off
     viewMatrix <<
       r.x(),       r.y(),       r.z(),       -r.dot(eye),
       u.x(),       u.y(),       u.z(),       -u.dot(eye),
-      -f.x(),      -f.y(),      -f.z(),      -f.dot(eye),
+      f.x(),       f.y(),       f.z(),       -f.dot(eye),
       Scalar(0),   Scalar(0),   Scalar(0),   Scalar(1);
     // clang-format on
   }
@@ -436,15 +436,15 @@ Eigen::Matrix<typename Derived::Scalar, 4, 4, Derived::Options> lookAtRh(const E
   return viewMatrix;
 }
 
-template <typename Derived>
+template <typename Derived, StorageOptions Options = StorageOptions::ColMajor>
 Eigen::Matrix<typename Derived::Scalar, 4, 4, Derived::Options> lookAtLh(const Eigen::MatrixBase<Derived>& eye,
                                                                          const Eigen::MatrixBase<Derived>& target,
                                                                          const Eigen::MatrixBase<Derived>& worldUp) {
   static_assert(Derived::RowsAtCompileTime == 3 && Derived::ColsAtCompileTime == 1, "lookAtLh requires 3x1 vectors.");
 
   using Scalar = typename Derived::Scalar;
-  using Vector3 = Eigen::Matrix<Scalar, 3, 1, Derived::Options>;
-  using Matrix4 = Eigen::Matrix<Scalar, 4, 4, Derived::Options>;
+  using Vector3 = Eigen::Matrix<Scalar, 3, 1, ::Eigen::ColMajor>;
+  using Matrix4 = Eigen::Matrix<Scalar, 4, 4, Options>;
 
   Vector3 f = (target - eye).normalized();
   Vector3 r = worldUp.cross(f).normalized();
@@ -1448,4 +1448,4 @@ Eigen::Matrix<T, 3, 1, Options> transformVector(const Eigen::Matrix<T, 3, 1, Opt
 }  // namespace Graphics
 }  // namespace Eigen
 
-#endif  // EIGEN_GRAPHICS_MODULE_H
\ No newline at end of file
+#endif  // EIGEN_GRAPHICS_MODULE_H