Setup projection matrix and position the quad properly

shaders/vert.glsl

@@ -4,10 +4,11 @@ layout(location=0) in vec3 position;
 layout(location=1) in vec3 vert_colour;
 
 uniform mat4 u_model;
+uniform mat4 u_projection;
 
 out vec3 vert_colours;
 
 void main() {
   vert_colours = vert_colour;
-  gl_Position = u_model * vec4(position, 1.0f);
+  gl_Position = u_projection * u_model * vec4(position, 1.0f);
 };

src/main.cc

@@ -1,5 +1,6 @@
 #include "glad/glad.h"
 #include "glm/gtc/type_ptr.hpp"
+#include "glm/trigonometric.hpp"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_error.h>
 #include <SDL2/SDL_video.h>
@@ -52,6 +53,10 @@ struct App {
   glm::mat4     model_mat;
   GLint         u_model_idx;
 
+  // Projection matrix to be sent as uniform to the vertex shader
+  glm::mat4     projection_mat;
+  GLint         u_projection_idx;
+
   bool          running;
 };
 
@@ -123,8 +128,13 @@ int init(App &app) {
          glGetString(GL_SHADING_LANGUAGE_VERSION)
   );
 
-  app.speed = 0.02f;
+  app.speed          = 0.02f;
-  app.model_mat = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f));
+  app.model_mat      = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f));
+  app.projection_mat = glm::perspective(glm::radians(60.0f),
+                                        (float)WINDOW_WIDTH / (float)WINDOW_HEIGHT,
+                                        0.1f,
+                                        20.0f
+                       );
 
   return EXIT_CODE_SUCCESS;
 }
@@ -132,17 +142,17 @@ int init(App &app) {
 void create_vertex_spec(App &app) {
   const std::vector<GLfloat> vertices = {
     // vert0
-    -0.5f, -0.5f, 0.0f, // position
+    -0.5f, -0.5f, -1.5f, // position
-     1.0f,  0.0f, 0.0f, // colour
+     1.0f,  0.0f,  0.0f, // colour
     // vert1
-     0.5f, -0.5f, 0.0f, // position
+     0.5f, -0.5f, -1.5f, // position
-     0.0f,  1.0f, 0.0f, // colour
+     0.0f,  1.0f,  0.0f, // colour
     // vert2
-    -0.5f,  0.5f, 0.0f, // position
+    -0.5f,  0.5f, -1.5f, // position
-     0.0f,  0.0f, 1.0f, // colour
+     0.0f,  0.0f,  1.0f, // colour
     // vert3
-     0.5f,  0.5f, 0.0f, // position
+     0.5f,  0.5f, -1.5f, // position
-     1.0f,  1.0f, 0.0f, // colour
+     1.0f,  1.0f,  0.0f, // colour
   };
 
   const std::vector<GLuint> indices = {
@@ -210,6 +220,12 @@ void create_graphics_pipeline(App &app) {
   if (app.u_model_idx < 0) {
     printf("Failed to find uniform %s\n", u_model);
   }
+
+  const char *u_projection = "u_projection";
+  app.u_projection_idx = glGetUniformLocation(app.shader_program, u_projection);
+  if (app.u_projection_idx < 0) {
+    printf("Failed to find uniform %s\n", u_projection);
+  }
 }
 
 void run_main_loop(App &app) {
@@ -242,6 +258,9 @@ void run_main_loop(App &app) {
     if (app.u_model_idx >= 0) {
       glUniformMatrix4fv(app.u_model_idx, 1, GL_FALSE, glm::value_ptr(app.model_mat));
     }
+    if (app.u_projection_idx >= 0) {
+      glUniformMatrix4fv(app.u_projection_idx, 1, GL_FALSE, glm::value_ptr(app.projection_mat));
+    }
     // End pre draw setup
 
     // Draw call