Spherical Harmonics Data in Volumetric Lightmap

Hey I’m trying to use the spherical harmonics data from the precomputed volumetric lightmap, but I’m a bit confused. From what I can tell, the data for each coefficient is just a single uint8, but there are only 6 coefficients, yet the documentation says that the data should be stored with a 3rd order SH, which would have 16 coefficients. Can someone explain how to reconstruct the SH function from the lightmap SH data?

Is 3rd order a reference to 2^3, which is 8?

Well I’d assume that 3rd order meant m = 3 and not m = 2, but even in the second case, you still don’t have enough coefficients. You would need 9 for m = 2.

How is the number of coefficients determined? I haven’t accessed that kind of information before. I’m really interested in understanding the volumetric lightmap data though.

For an order m SH you need (m + 1)^2 coefficients, but I’m not sure how the lightmap data contains their SH data.