few shader updates.

src/6.pbr/2.2.1.ibl_specular/2.2.1.background.frag

@@ -3,12 +3,10 @@ out vec4 FragColor;
 in vec3 WorldPos;
 
 uniform samplerCube environmentMap;
-uniform float lod;
 
 void main()
 {		
-    // vec3 envColor = textureLod(environmentMap, WorldPos, 1.0).rgb;
-    vec3 envColor = textureLod(environmentMap, WorldPos, lod).rgb;
+    vec3 envColor = textureLod(environmentMap, WorldPos, 0.0).rgb;
     
     // HDR tonemap and gamma correct
     envColor = envColor / (envColor + vec3(1.0));

src/6.pbr/2.2.1.ibl_specular/2.2.1.irradiance_convolution.frag

@@ -8,16 +8,11 @@ const float PI = 3.14159265359f;
 
 void main()
 {		
-	// NOTE(Joey): the world vector acts as the normal of a tangent surface
-    // from the origin, aligned to WorldPos. Given this normal, calculate all
-    // incoming radiance of the environment. The result of this radiance
-    // is the radiance of light coming from -Normal direction, which is what
-    // we use in the PBR shader to sample irradiance.
     vec3 N = normalize(WorldPos);
 
     vec3 irradiance = vec3(0.0);   
     
-    // NOTE(Joey): tangent space calculation from origin point
+    // tangent space calculation from origin point
     vec3 up    = vec3(0.0, 1.0, 0.0);
     vec3 right = cross(up, N);
     up            = cross(N, right);