Now have anti-aliasing with framebuffers and can do post processing on it. Look at shaders/30-screen-bw.frag.glsl to see.

30-anti-aliasing/shaders/30-screen-bw.frag.glsl

@@ -0,0 +1,13 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec2 TexCoords;
+
+uniform sampler2D screenTexture;
+
+void main()
+{
+    vec3 col = texture(screenTexture, TexCoords).rgb;
+    float grayscale = 0.2126 * col.r + 0.7152 * col.g + 0.0722 * col.b;
+    FragColor = vec4(vec3(grayscale), 1.0);
+}

30-anti-aliasing/shaders/30-screen.frag.glsl

@@ -0,0 +1,11 @@
+#version 330 core
+out vec4 FragColor;
+
+in vec2 TexCoords;
+
+uniform sampler2D screenTexture;
+
+void main()
+{
+    FragColor = texture(screenTexture, TexCoords);
+}

30-anti-aliasing/shaders/30-screen.vert.glsl

@@ -0,0 +1,11 @@
+#version 330 core
+layout (location = 0) in vec2 aPos;
+layout (location = 1) in vec2 aTexCoords;
+
+out vec2 TexCoords;
+
+void main()
+{
+    gl_Position = vec4(aPos.x, aPos.y, 0.0, 1.0);
+    TexCoords = aTexCoords;
+}