returns the environment radiance (linear RGB) for a unit direction (x, y, z).
number of sphere samples (more = lower variance).
Hann window width applied per band to suppress low-order
ringing (see shBandWindow); 0 (default) leaves the coefficients
un-windowed. Must match the GPU bake's window parameter.
27 floats: 9 coefficients × RGB, the raw projection L_lm. Pass to evalShIrradiance or packShForGpu.
Projects an environment onto order-3 SH on the CPU using a deterministic Fibonacci-sphere sample set (uniform over the sphere, solid-angle weight 4π/N per sample). This is the reference/offline projector; the engine bakes the same integral on the GPU.