From ef03920fa62e7c92383d00e195dfcd23073c7418 Mon Sep 17 00:00:00 2001
From: Archie Hilton <archie.hilton1@gmail.com>
Date: Fri, 10 May 2024 22:23:35 +0100
Subject: [PATCH] Add rotation and translation uniforms

---
 src/main.cc             | 72 +++++++++++++++++++++++++----------------
 src/shaders/shader.vert | 11 +++----
 2 files changed, 50 insertions(+), 33 deletions(-)

diff --git a/src/main.cc b/src/main.cc
index 6c2c6af..f335856 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -8,10 +8,16 @@
 #include <string>
 #include <vector>
 
+#include <array>
+
 // This has to come last.
 #define GLAD_GL_IMPLEMENTATION
 #include <glad/gl.h>
 
+#include <glm/glm.hpp>
+#include <glm/ext.hpp>
+#include <glm/mat2x2.hpp>
+
 static void dbg_log(const char* str) {
     std::cout << str << std::endl;
 }
@@ -27,7 +33,8 @@ static void key_callback(GLFWwindow *w, int key, int scancode, int action, int m
 
 GLuint g_program_id = 0;
 
-static GLuint time_unif;
+static GLuint translate_unif;
+static GLuint rotate_unif;
 
 static void init_shaders() {
     dbg_log("Initialising shaders");
@@ -47,36 +54,55 @@ static void init_shaders() {
 
     glUseProgram(g_program_id);
 
-    glGetUniformLocation(g_program_id, "time");
+    translate_unif = glGetUniformLocation(g_program_id, "world_pos");
+    rotate_unif = glGetUniformLocation(g_program_id, "rotation");
 }
 
-static const GLfloat verts[6] = {
-    0.0f, 0.0f, 0.0f, 0.5f, 0.5f, 0.0f
+class Triangle {
+public:
+    GLfloat data[6];
+    float m_pos_x;
+    float m_pos_y;
+    float rotation = 0.2f;
+
+    Triangle(std::array<glm::vec2, 3> verts) {
+        for (std::size_t i = 0; i < 3; i++) {
+            data[i*2] = verts[i][0];
+            data[i*2+1] = verts[i][1];
+        }
+    }
+
+    std::array<float, 2> get_world_projection() {
+        return std::array<float, 2>({m_pos_x, m_pos_y});
+    }
 };
 
-static GLuint vertex_buf;
-static GLuint array_buf;
+static GLuint vertex_buf[2];
+static GLuint array_buf[2];
 static const GLuint vertex_data_position = 0;
 
+static Triangle o1(std::array<glm::vec2, 3>({
+        {0.0f, 0.0f},
+        {0.5f, 0.0f},
+        {0.5f, 0.5f}
+    }));
+
 // Do the work of initialising opengl so we can draw stuff
 static void init_opengl() {
     dbg_log("Initialising opengl");
     // Configure the context's capabilities
     glClearColor(0.0, 0.0, 0.0, 1.0);
 
-    glGenVertexArrays(1, &array_buf);
-    glBindVertexArray(array_buf);
-
-    glGenBuffers(1, &vertex_buf);
-    glBindBuffer(GL_ARRAY_BUFFER, vertex_buf);
-    glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STATIC_DRAW);
-
-
-    init_shaders();
+    glGenVertexArrays(2, array_buf);
+    glBindVertexArray(array_buf[0]);
 
+    glGenBuffers(2, vertex_buf);
+    glBindBuffer(GL_ARRAY_BUFFER, vertex_buf[0]);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(Triangle::data), o1.data, GL_STATIC_DRAW);
     glVertexAttribPointer(vertex_data_position, 2, GL_FLOAT, GL_FALSE, 0, NULL);
     glEnableVertexAttribArray(vertex_data_position);
 
+    init_shaders();
 }
 
 int main() {
@@ -107,23 +133,15 @@ int main() {
     
     // Main Loop
     while(!glfwWindowShouldClose(w)) {
-        /*
-        int width, height;
-        glfwGetFramebufferSize(w, &width, &height);
-
-        glViewport(0, 0, width, height);
-        glClear(GL_COLOR_BUFFER_BIT);
-        */
-
        float time = glfwGetTime();
 
         glClear(GL_COLOR_BUFFER_BIT);
 
-        glUniform1f(time_unif, time);
-        glBindVertexArray(array_buf);
-        glDrawArrays(GL_TRIANGLES, 0, 3);
+        glUniform2fv(translate_unif, 1, o1.get_world_projection().data());
+        glUniform1f(rotate_unif, o1.rotation);
 
-        // TODO Draw primitives
+        glBindVertexArray(array_buf[0]);
+        glDrawArrays(GL_TRIANGLES, 0, 3);
 
         glfwSwapBuffers(w);
         glfwPollEvents();
diff --git a/src/shaders/shader.vert b/src/shaders/shader.vert
index 6958689..d98894b 100644
--- a/src/shaders/shader.vert
+++ b/src/shaders/shader.vert
@@ -2,15 +2,14 @@
 
 layout (location = 0) in vec4 v_position;
 
-uniform float time;
+uniform vec2 world_pos;
+uniform float rotation;
 
 // Simple passthrough shader for now.
 void main() {
-    vec2 new_xy = v_position.xy * mat2x2(
-        cos(time), -sin(time),
-        sin(time), cos(time)
-    );
-    
+    mat2x2 rot_mat = mat2x2(cos(rotation), sin(rotation), -sin(rotation), cos(rotation));
+
+    vec2 new_xy = v_position.xy * rot_mat + world_pos;
     vec4 new_position = vec4(new_xy.x, new_xy.y, 0.0, 1.0);
 
     gl_Position = new_position;