Use uniforms for color

main.c

@@ -12,7 +12,6 @@
 #define log_err(str, ...) do { fprintf(stderr, "[ERROR] (%s:%d): " str "\n", __FILE__, __LINE__, ##__VA_ARGS__); } while (0)
 #define log_debug(str, ...) do { fprintf(stderr, "[DEBUG] (%s:%d): " str "\n", __FILE__, __LINE__, ##__VA_ARGS__); } while (0)
 
-
 char *read_entire_file(char *path)
 {
     FILE *f = fopen(path, "rb");
@@ -38,7 +37,13 @@ static void glfw_error_callback(int errcode, const char *description)
     fprintf(stderr, "[GLFW ERROR][ERRCODE %d] %s\n", errcode, description);
 }
 
-int main()
+void set_uniform(GLuint program_id, const char *name, vec4f value)
+{
+    GLint location = glGetUniformLocation(program_id, name);
+    glUniform4f(location, value.x, value.y, value.z, value.w);
+}
+
+int main(void)
 {
     GLFWwindow *window;
 
@@ -61,7 +66,7 @@ int main()
 
     char * vertexShaderSource = read_entire_file("shaders/vertex.glsl");
     char *fragmentShaderSource = read_entire_file("shaders/fragment.glsl");
-    
+
     // vertex shader
     unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
     glShaderSource(vertex_shader, 1, &vertexShaderSource, NULL);
@@ -106,8 +111,6 @@ int main()
     background_color.b = 0.3f;
     background_color.a = 1.0f;
 
-
-
     hexgrid_t grid;
     grid.rows = 2;
     grid.columns = 2;
@@ -181,6 +184,7 @@ int main()
     //glBindBuffer(GL_ARRAY_BUFFER, 0);
     //glBindVertexArray(0);
 
+    int64_t framecount = 0;
     while (!glfwWindowShouldClose(window))
     {
         int width, height;
@@ -193,6 +197,15 @@ int main()
         glUseProgram(shader_program);
         //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
 
+        // Set uniforms
+        vec4f hex_color;
+        hex_color.r = (float)(framecount % 1100)/1100;
+        hex_color.g = (float)(framecount % 300)/300;
+        hex_color.b = (float)(framecount % 1700)/1700;
+        hex_color.a = 1.0f;
+
+        set_uniform(shader_program, "uniform_color", hex_color);
+
         for (size_t i = 0; i < grid.rows * grid.columns; ++i)
         {
             glBindVertexArray(grid.hexes[i].vao);
@@ -203,5 +216,8 @@ int main()
         }
         glfwPollEvents();
         glfwSwapBuffers(window);
+
+        ++framecount;
     }
+    return 0;
 }

shaders/fragment.glsl

@@ -1,6 +1,7 @@
 #version 330 core
-out vec4 color;
+in vec4 vertex_color;
+out vec4 final_color;
 void main()
 {
-    color = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+    final_color = vertex_color;
 }

shaders/vertex.glsl

@@ -1,6 +1,9 @@
 #version 330 core
 layout (location = 0) in vec3 pos;
+uniform vec4 uniform_color;
+out vec4 vertex_color;
 void main()
 {
     gl_Position = vec4(pos, 1.0f);
+    vertex_color = uniform_color;
 }