refactor: extract uniform updates from triangle

src/hello.cpp

@@ -35,7 +35,8 @@
 // cmake ..
 // cmake --build .
 
-#include <glm/glm.hpp>
+#include "glm/glm.hpp"
+#include "glm/gtc/matrix_transform.hpp"
 #include <GL/glew.h>
 #include <GLFW/glfw3.h>
 
@@ -81,6 +82,43 @@ int initGraphics(GLFWwindow** window)
     return 0;
 }
 
+GLint getShaderUniformLocation(GLuint shaderProgram, const std::string& uniformName)
+{
+    GLint location = glGetUniformLocation(shaderProgram, uniformName.c_str());
+    if (location == -1)
+    {
+        std::cerr << "Could not find uniform: " << uniformName << std::endl;
+        return -1;
+    }
+
+    return location;
+}
+
+void updateModelViewProjectionMatrix(GLuint shaderProgram, 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;
+
+    GLint mvpLocation = getShaderUniformLocation(shaderProgram, "_ModelViewProjectionMatrix");
+    glUniformMatrix4fv(mvpLocation, 1, GL_FALSE, &mvp[0][0]);
+}
+
+void updateTime(GLuint shaderProgram, float time)
+{
+	GLint timeLocation = getShaderUniformLocation(shaderProgram, "_Time");
+	float timeValue = time;
+	glUniform1f(timeLocation, timeValue);
+}
+
 int main()
 {
     // Calculate period of ISS orbit around the Earth
@@ -98,8 +136,8 @@ int main()
         return -1;
 
     GLuint shaderProgram = compileShaderProgram();
-    Triangle triangle(shaderProgram);
-    Icosphere sphere(shaderProgram, 0);
+    Triangle triangle;
+    Icosphere sphere(0);
 
     // Wireframe
     glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
@@ -110,7 +148,15 @@ int main()
         glClearColor(0.2, 0.3, 0.3, 1.0);
         glClear(GL_COLOR_BUFFER_BIT);
 
+        // Render everything with the same shaders
+        glUseProgram(shaderProgram);
+
+        // Update uniforms
         float time = glfwGetTime();
+        updateTime(shaderProgram, time);
+        updateModelViewProjectionMatrix(shaderProgram, time);
+
+        // Render objects
         triangle.render(time);
         sphere.render(time);
 

src/icosphere.cpp

@@ -2,8 +2,7 @@
 
 #include <iostream>
 
-Icosphere::Icosphere(GLuint shaderProgram, int subdivisions)
-	: _shaderProgram(shaderProgram)
+Icosphere::Icosphere(int subdivisions)
 {
 	glGenVertexArrays(1, &_vao);
 	glGenBuffers(1, &_vbo);
@@ -39,8 +38,6 @@ Icosphere::Icosphere(GLuint shaderProgram, int subdivisions)
 
 void Icosphere::render(float time)
 {
-	glUseProgram(_shaderProgram);
-
 	glBindVertexArray(_vao);
 	glBindBuffer(GL_ARRAY_BUFFER, _vbo);
 	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _ebo);

src/icosphere.hpp

@@ -9,7 +9,7 @@
 class Icosphere
 {
 public:
-	Icosphere(GLuint shaderProgram, int subdividision);
+	Icosphere(int subdividision);
 	void render(float time);
 
 	~Icosphere();
@@ -18,7 +18,6 @@ private:
 	GLuint _vbo;
 	GLuint _vao;
 	GLuint _ebo;
-	GLuint _shaderProgram;
 
 	std::vector<float> _vertices;
 	std::vector<unsigned int> _indices;
@@ -49,6 +48,4 @@ private:
 		{7,10,3},{7,6,10},{7,11,6},{11,0,6},{0,1,6},
 		{6,1,10},{9,0,11},{9,11,2},{9,2,5},{7,2,11}
 	};
-
-	GLint getShaderUniformLocation(const std::string& uniformName);
 };

src/triangle.cpp

@@ -2,11 +2,7 @@
 
 #include <iostream>
 
-#include "glm/glm.hpp"
-#include "glm/gtc/matrix_transform.hpp"
-
-Triangle::Triangle(GLuint shaderProgram)
-    : _shaderProgram(shaderProgram)
+Triangle::Triangle()
 {
     glGenVertexArrays(1, &_vao);
     glGenBuffers(1, &_vbo);
@@ -25,44 +21,11 @@ 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 mvpLocation = getShaderUniformLocation("_ModelViewProjectionMatrix");
-    glUniformMatrix4fv(mvpLocation, 1, GL_FALSE, &mvp[0][0]);
-
-	GLint timeLocation = getShaderUniformLocation("_Time");
-	float timeValue = time;
-	glUniform1f(timeLocation, timeValue);
-
 	glBindVertexArray(_vao);
 	glBindBuffer(GL_ARRAY_BUFFER, _vbo);
 	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 -1;
-    }
-
-    return location;
-}
-
 Triangle::~Triangle()
 {
     glDeleteVertexArrays(1, &_vao);

src/triangle.hpp

@@ -8,7 +8,7 @@
 class Triangle
 {
 public:
-	Triangle(GLuint shaderProgram);
+	Triangle();
 	void render(float time);
 
 	~Triangle();
@@ -16,7 +16,6 @@ public:
 private:
 	GLuint _vbo;
 	GLuint _vao;
-	GLuint _shaderProgram;
 
 	std::vector<float> _vertices =
 	{