# Spherical Area Lights do not match reference

So I'm adding spherical area lights to my application, and comparing my results with mitsuba, I am getting some differences (left is my approach, right is mitsuba - a pathtraced reference):

What I am mainly noticing is that:

1. The specular is way too bright for roughness values over 0.5

2. The specular shape gets "flat" (Left-mine, Right-mitsuba, noise caused by low sample count):

I am using the closest point approximation and the normalization term proposed in Real Shading in UE4, that is: (radius / (distance * 2.0) + alpha)²

I believe issue 1) could be an issue with my normalization term, however I think issue 2) might probably be an issue with the closest point approximation?

Is this kind of inaccuracy expected with the approximations I use, and if so, are there better approximations?

• For context could you show us the rest of your Implementation please. – Thomas Mathieson Oct 29 '17 at 10:42
• you haven't provided us enough code for us to actually help you. – Krupip Mar 23 '18 at 17:19