Update PBR lighting chapter to support large DGGX values as 0-clamp was too high.

src/6.pbr/1.1.lighting/1.1.pbr.fs

@@ -29,7 +29,7 @@ float DistributionGGX(vec3 N, vec3 H, float roughness)
     float denom = (NdotH2 * (a2 - 1.0) + 1.0);
     denom = PI * denom * denom;
 
-    return nom / max(denom, 0.001); // prevent divide by zero for roughness=0.0 and NdotH=1.0
+    return nom / max(denom, 0.0000001); // prevent divide by zero for roughness=0.0 and NdotH=1.0
 }
 // ----------------------------------------------------------------------------
 float GeometrySchlickGGX(float NdotV, float roughness)

src/6.pbr/1.1.lighting/lighting.cpp

@@ -140,7 +140,7 @@ int main()
             shader.setFloat("metallic", (float)row / (float)nrRows);
             for (int col = 0; col < nrColumns; ++col) 
             {
-                // we clamp the roughness to 0.025 - 1.0 as perfectly smooth surfaces (roughness of 0.0) tend to look a bit off
+                // we clamp the roughness to 0.05 - 1.0 as perfectly smooth surfaces (roughness of 0.0) tend to look a bit off
                 // on direct lighting.
                 shader.setFloat("roughness", glm::clamp((float)col / (float)nrColumns, 0.05f, 1.0f));