Function transmittance

transmittance(
    a: AtmosphereOptions,
    planetRadius: number,
    p: Vec3,
    d: Vec3,
): Vec3
Fraction of light (per channel) surviving from p along d out to space; zeros if the planet blocks it.
Parameters
- a: AtmosphereOptions
- planetRadius: number
- p: Vec3
- d: Vec3
Returns Vec3
- Defined in sky/src/scattering.ts:142