From 68d63edef7a80b64152a1415ff41d20b81867d78 Mon Sep 17 00:00:00 2001
From: Cat Flynn <me@ktyl.dev>
Date: Mon, 31 Jul 2023 23:30:35 +0200
Subject: [PATCH] feat: orthographic triangle

---
 src/triangle.cpp | 37 +++++++++++++++++++++++++++++++------
 src/triangle.hpp |  3 +++
 vert.glsl        |  5 ++++-
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/src/triangle.cpp b/src/triangle.cpp
index 41c56f9..976e2be 100644
--- a/src/triangle.cpp
+++ b/src/triangle.cpp
@@ -2,6 +2,9 @@
 
 #include <iostream>
 
+#include "glm/glm.hpp"
+#include "glm/gtc/matrix_transform.hpp"
+
 Triangle::Triangle(GLuint shaderProgram)
     : _shaderProgram(shaderProgram)
 {
@@ -22,14 +25,24 @@ Triangle::Triangle(GLuint shaderProgram)
 
 void Triangle::render(float time)
 {
+    // Calculate matrices
+    float left = -1.0, right = 1.0, bottom = -1.0, top = 1.0, near = -1.0, far = 1.0;
+    glm::mat4 projection = glm::ortho(left, right, bottom, top, near, far);
+
+    constexpr float angle = glm::radians(50.0);
+    glm::vec3 axis = glm::vec3(0.0, 1.0, 0.0);
+    glm::mat4 model = glm::rotate(glm::mat4(1.0), angle * time, axis);
+
+    glm::mat4 view = glm::mat4(1.0);
+
+    glm::mat4 mvp = projection * model * view;
+
 	glUseProgram(_shaderProgram);
 
-	GLint timeLocation = glGetUniformLocation(_shaderProgram, "_Time");
-	if (timeLocation == -1)
-	{
-		std::cerr << "Could not find uniform: _Time" << std::endl;
-        return;
-	}
+    GLint mvpLocation = getShaderUniformLocation("_ModelViewProjectionMatrix");
+    glUniformMatrix4fv(mvpLocation, 1, GL_FALSE, &mvp[0][0]);
+
+	GLint timeLocation = getShaderUniformLocation("_Time");
 	float timeValue = time;
 	glUniform1f(timeLocation, timeValue);
 
@@ -38,6 +51,18 @@ void Triangle::render(float time)
 	glDrawArrays(GL_TRIANGLES, 0, 3);
 }
 
+GLint Triangle::getShaderUniformLocation(const std::string& uniformName)
+{
+    GLint location = glGetUniformLocation(_shaderProgram, uniformName.c_str());
+    if (location == -1)
+    {
+        std::cerr << "Could not find uniform: " << uniformName << std::endl;
+        return 0;
+    }
+
+    return location;
+}
+
 Triangle::~Triangle()
 {
     glDeleteVertexArrays(1, &_vao);
diff --git a/src/triangle.hpp b/src/triangle.hpp
index 4e02e4f..9ffea5d 100644
--- a/src/triangle.hpp
+++ b/src/triangle.hpp
@@ -3,6 +3,7 @@
 #include <GL/glew.h>
 
 #include <vector>
+#include <string>
 
 class Triangle
 {
@@ -23,4 +24,6 @@ private:
          0.5, -0.5, 0.0,    // right
          0.0,  0.5, 0.0     // top
 	};
+
+	GLint getShaderUniformLocation(const std::string& uniformName);
 };
\ No newline at end of file
diff --git a/vert.glsl b/vert.glsl
index aaa01ad..96316d1 100644
--- a/vert.glsl
+++ b/vert.glsl
@@ -2,8 +2,11 @@
 
 layout (location = 0) in vec3 aPos;
 
+uniform mat4x4 _ModelViewProjectionMatrix;
+
 void main()
 {
-    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    vec4 pos = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+    gl_Position = _ModelViewProjectionMatrix * pos;
 }