Add the glm math library and use matrices to transform the object

meson.build

@@ -2,5 +2,6 @@ project('opengl-learning', 'cpp', 'c', default_options: ['cpp_std=c++20'])
 
 glfw = dependency('glfw3')
 libepoxy = dependency('epoxy')
+glm = dependency('glm')
 
 subdir('src')

src/main.cc

@@ -1,5 +1,7 @@
 #include <epoxy/gl.h>
 #include <GLFW/glfw3.h>
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
 
 #include <iostream>
 #include <format>
@@ -202,6 +204,10 @@ int main() {
 	shader.setInt("texture1", 0);
 	shader.setInt("texture2", 1);
 
+	// glm::mat4 trans = glm::mat4(1.0f);
+	// trans = glm::rotate(trans, glm::radians(90.0f), glm::vec3(0.0, 0.0, 1.0));
+	// trans = glm::scale(trans, glm::vec3(0.5, 0.5, 0.5));
+
 	// Create a render loop, which keeps the program open until glfw tells the loop that the window should close.
 	while (!glfwWindowShouldClose(window)) {
 		// Process input.
@@ -224,6 +230,15 @@ int main() {
 
 		shader.activate();
 
+		// create the identity matrix
+		glm::mat4 trans(1);
+		// translate it by this vector3
+		trans = glm::translate(trans, glm::vec3(0.5f, -0.5f, 0.0f));
+		// rotate by the z axis with the angle being controlled by time
+		trans = glm::rotate(trans, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));
+
+		shader.setMat4("transform", trans);
+
 		if (!rectangleToggled) {
 			// Bind the state to use the vertexArrayObject object so OpenGL knows what to do with the verticies.
 			glBindVertexArray(triangleRenderObjs.vertexArrayObject);

src/meson.build

@@ -12,5 +12,5 @@ vertex = custom_target('vertex', output: 'vertex.glsl', input: 'vertex.glsl', co
 container = custom_target('container', output: 'container.jpg', input: 'container.jpg', command: [copy, '@INPUT@', '@OUTPUT@'])
 awesomeface = custom_target('awesomeface', output: 'awesomeface.png', input: 'awesomeface.png', command: [copy, '@INPUT@', '@OUTPUT@'])
 
-executable('main', [sources, fragment, vertex, container, awesomeface], dependencies: [glfw, libepoxy])
+executable('main', [sources, fragment, vertex, container, awesomeface], dependencies: [glfw, libepoxy, glm])
 executable('fixedfunction', ['fixedfunction.cc'], dependencies: [glfw, libepoxy])

src/shader.cc

@@ -103,3 +103,7 @@ void Shader::setInt(const char* name, int value)  {
 void Shader::setFloat(const char* name, float value) const {
 	glUniform1f(glGetUniformLocation(id, name), value);
 }
+
+void Shader::setMat4(const char* name, glm::mat4 matrix) {
+	glUniformMatrix4fv(glGetUniformLocation(id, name), 1, GL_FALSE, glm::value_ptr(matrix));
+}

src/shader.hh

@@ -2,6 +2,9 @@
 #define SHADER_HH
 #include <string>
 #include <epoxy/gl.h>
+#include <glm/glm.hpp>
+#include <glm/gtc/type_ptr.hpp>
+
 class Shader {
 	public:
 	// The Shader ID.
@@ -17,6 +20,7 @@ class Shader {
 	void setBool(const char* name, bool value) const;  
 	void setInt(const char* name, int value) ;   
 	void setFloat(const char* name, float value) const;
+	void setMat4(const char* name, glm::mat4 matrix);
 	private:
 	uint compileShader(std::string code, GLenum type, std::string shaderTypeName);
 	uint compileVertexShader(std::string code);

src/vertex.glsl

@@ -7,8 +7,10 @@ layout (location = 2) in vec2 aTexCoord;
 out vec3 ourColor;
 out vec2 TexCoord;
 
+uniform mat4 transform;
+
 void main() {
-	gl_Position = vec4(aPos, 1.0);
+	gl_Position = transform * vec4(aPos, 1.0);
 	ourColor = aColor;
 	TexCoord = aTexCoord;
 }