A library for creating and manipulating spherical and zonal harmonics.
Provides the usual utilities for projecting environments into SH coefficients, evaluating them, and performing cheap(ish) operations such as symmetric rotation and mirroring. Also contains a set of zonal harmonics routines for constructing rotationally-symmetric BRDFs which can then be rotated into the full 3D spherical harmonics space along a particular direction, or convolved with a set of spherical harmonics.
The focus is on fast(ish) code for low band counts, so a number of routines rely on pregenerated code, and only support up to a certain band count, usually at least 5 (SH) or 7 (ZH). This is noted in the comments where it applies.
To build and run the test app:
c++ ZHLib.cpp SHLib.cpp SHLibTest.cpp -o shtest && ./shtest
Or add those files to your favourite IDE.
See the shaders directory for some of these routines recast in GLSL. There is a corresponding shader toy demo.