Refactor shaders

data/shaders/post_processing.vert

@@ -0,0 +1,12 @@
+#version 330 core
+
+out vec2 v_tex_coords;
+
+void main()
+{
+    float x = -1.0 + float((gl_VertexID & 1) << 2);
+    float y = -1.0 + float((gl_VertexID & 2) << 1);
+    v_tex_coords.x = (x + 1.0) * 0.5;
+    v_tex_coords.y = (y + 1.0) * 0.5;
+    gl_Position = vec4(x, y, 0, 1);
+}