feat: add time uniform to shader

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.27)
-project(HelloGLEW)
+project(HelloTriangle)
 
 # Define platform-specific paths and libraries
 if(WIN32)

frag.glsl

@@ -2,7 +2,9 @@
 
 out vec4 FragColor;
 
+uniform float _Time;
+
 void main()
 {
-    FragColor = vec4(1.0, 0.5, 0.2, 1.0);
+    FragColor = vec4(1.0, 0.5, 0.2, 1.0) * sin(_Time) / 2.0 + 0.5;
 }

hello.cpp

@@ -40,6 +40,8 @@
 #include <sstream>
 #include <string>
 
+#include <chrono>
+
 std::string readFile(const std::string& filePath)
 {
     std::ifstream fileStream(filePath, std::ios::in);
@@ -82,13 +84,21 @@ GLuint compileShader(const std::string& shaderPath, GLenum shaderType)
     return shader;
 }
 
+std::chrono::steady_clock::time_point startTime = std::chrono::steady_clock::now();
+float getTime()
+{
+    std::chrono::steady_clock::time_point now = std::chrono::steady_clock::now();
+    std::chrono::duration<float> timeSpan = std::chrono::duration_cast<std::chrono::duration<float>>(now - startTime);
+    return timeSpan.count();
+}
+
 int main()
 {
     // Set up GLFW, OpenGL and GLEW.
     if (!glfwInit())
         return -1;
 
-    GLFWwindow* window = glfwCreateWindow(640, 480, "Hello GLEW", NULL, NULL);
+    GLFWwindow* window = glfwCreateWindow(640, 480, "Hello Triangle", NULL, NULL);
     if (!window)
     {
         glfwTerminate();
@@ -150,12 +160,22 @@ int main()
     glDeleteShader(vertShader);
     glDeleteShader(fragShader);
 
+    // Main loop
     while (!glfwWindowShouldClose(window))
     {
         glClearColor(0.2, 0.3, 0.3, 1.0);
         glClear(GL_COLOR_BUFFER_BIT);
 
         glUseProgram(shaderProgram);
+
+        GLint timeLocation = glGetUniformLocation(shaderProgram, "_Time");
+        if (timeLocation == -1)
+        {
+            std::cerr << "Could not find uniform: _Time" << std::endl;
+        }
+        float timeValue = getTime();
+        glUniform1f(timeLocation, timeValue);
+
         glBindVertexArray(VAO);
         glDrawArrays(GL_TRIANGLES, 0, 3);