From 1f284ed349317281506868d5f8efbbc51b644eee Mon Sep 17 00:00:00 2001
From: David Allemang <david.allemang@kitware.com>
Date: Fri, 27 Jan 2023 22:28:39 -0500
Subject: [PATCH] ENH: Replace GLM with Eigen

---
 CMakeLists.txt         |  4 ++--
 vendor/eigen.cmake     | 10 ++++++++++
 vendor/glm.cmake       |  8 --------
 vis/CMakeLists.txt     |  2 +-
 vis/include/mirror.hpp | 34 +++++++++++++++++++++++++++-------
 vis/src/main.cpp       | 14 +++++++-------
 6 files changed, 47 insertions(+), 25 deletions(-)
 create mode 100644 vendor/eigen.cmake
 delete mode 100644 vendor/glm.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 35abe80..5bd3782 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,12 +4,12 @@ project(toddcox-faster)
 set(CMAKE_CXX_STANDARD 20)
 
 include(FetchContent)
+include(vendor/eigen.cmake)
 include(vendor/fmt.cmake)
-include(vendor/peglib.cmake)
 include(vendor/glad.cmake)
 include(vendor/glfw.cmake)
-include(vendor/glm.cmake)
 include(vendor/gtest.cmake)
+include(vendor/peglib.cmake)
 include(vendor/yaml-cpp.cmake)
 
 include(vendor/embed.cmake)
diff --git a/vendor/eigen.cmake b/vendor/eigen.cmake
new file mode 100644
index 0000000..f84f496
--- /dev/null
+++ b/vendor/eigen.cmake
@@ -0,0 +1,10 @@
+FetchContent_Declare(
+    eigen
+    GIT_REPOSITORY https://gitlab.com/libeigen/eigen.git
+    GIT_TAG 3.4
+    GIT_PROGRESS TRUE
+)
+set(EIGEN_BUILD_DOC OFF CACHE INTERNAL "")
+set(BUILD_TESTING OFF CACHE INTERNAL "")
+set(EIGEN_BUILD_PKGCONFIG OFF CACHE INTERNAL "")
+FetchContent_MakeAvailable(eigen)
diff --git a/vendor/glm.cmake b/vendor/glm.cmake
deleted file mode 100644
index ebc1655..0000000
--- a/vendor/glm.cmake
+++ /dev/null
@@ -1,8 +0,0 @@
-FetchContent_Declare(
-    glm
-    GIT_REPOSITORY https://github.com/g-truc/glm.git
-    GIT_TAG 0.9.9.8
-    GIT_PROGRESS TRUE
-)
-
-FetchContent_MakeAvailable(glm)
diff --git a/vis/CMakeLists.txt b/vis/CMakeLists.txt
index 52debce..d99c423 100644
--- a/vis/CMakeLists.txt
+++ b/vis/CMakeLists.txt
@@ -19,5 +19,5 @@ target_include_directories(vis-util INTERFACE include)
 
 add_executable(vis src/main.cpp)
 target_include_directories(vis PRIVATE include)
-target_link_libraries(vis PRIVATE tc glad glm glfw yaml-cpp shaders)
+target_link_libraries(vis PRIVATE tc glad eigen glfw yaml-cpp shaders fmt)
 add_dependencies(vis presets)
diff --git a/vis/include/mirror.hpp b/vis/include/mirror.hpp
index 04f304e..b3af23a 100644
--- a/vis/include/mirror.hpp
+++ b/vis/include/mirror.hpp
@@ -6,6 +6,8 @@
 #include <vector>
 #include <algorithm>
 
+#include <Eigen/Eigen>
+
 template<unsigned N>
 using vec = std::array<float, N>;
 
@@ -184,11 +186,29 @@ std::vector<V> plane_intersections(std::vector<V> normals) {
     return results;
 }
 
-glm::mat4 utilRotate(const int u, const int v, const float theta) {
-    auto res = glm::identity<glm::mat4>();
-    res[u][u] = std::cos(theta);
-    res[u][v] = std::sin(theta);
-    res[v][u] = -std::sin(theta);
-    res[v][v] = std::cos(theta);
+Eigen::Matrix4f utilRotate(const int u, const int v, const float theta) {
+    Eigen::Matrix4f res;
+    res.setIdentity();
+    res(u, u) = std::cos(theta);
+    res(u, v) = std::sin(theta);
+    res(v, u) = -std::sin(theta);
+    res(v, v) = std::cos(theta);
     return res;
-}
\ No newline at end of file
+}
+
+Eigen::Matrix4f ortho(
+    float l,
+    float r,
+    float b,
+    float t,
+    float n,
+    float f
+) {
+    Eigen::Matrix4f res;
+    res <<
+        2 / (r - l), 0, 0, -(r + l) / (r - l),
+        0, 2 / (t - b), 0, -(t + b) / (t - b),
+        0, 0, -2 / (f - n), -(f + n) / (f - n),
+        0, 0, 0, 1;
+    return res;
+}
diff --git a/vis/src/main.cpp b/vis/src/main.cpp
index 6a8d3bf..ae2c606 100644
--- a/vis/src/main.cpp
+++ b/vis/src/main.cpp
@@ -3,8 +3,6 @@
 #include <cmath>
 #include <iostream>
 
-#include <glm/gtc/type_ptr.hpp>
-
 #include <tc/groups.hpp>
 
 #include "util.hpp"
@@ -28,10 +26,10 @@ __attribute__((unused)) __declspec(dllexport) int NvOptimusEnablement = 0x000000
 #endif
 
 struct Matrices {
-    glm::mat4 proj;
-    glm::mat4 view;
+    Eigen::Matrix4f proj;
+    Eigen::Matrix4f view;
 
-    Matrices(const glm::mat4 &proj, const glm::mat4 &view)
+    Matrices(const Eigen::Matrix4f &proj, const Eigen::Matrix4f &view)
         : proj(proj), view(view) {
     }
 };
@@ -52,13 +50,15 @@ Matrices build(GLFWwindow *window, State &state) {
     auto aspect = (float) width / (float) height;
     auto pheight = 1.4f;
     auto pwidth = aspect * pheight;
-    glm::mat4 proj = glm::ortho(-pwidth, pwidth, -pheight, pheight, -10.0f, 10.0f);
+    Eigen::Matrix4f proj = ortho(-pwidth, pwidth, -pheight, pheight, -10.0f, 10.0f);
 
     if (!glfwGetKey(window, GLFW_KEY_LEFT_SHIFT)) {
         state.st += state.time_delta / 8;
     }
 
-    auto view = glm::identity<glm::mat4>();
+    Eigen::Matrix4f view;
+    view.setIdentity();
+
     if (state.dimension < 4) {
         view *= utilRotate(2, 3, M_PI_2f32 + 0.01f);
     }