Contents
What do light probes do?
The primary use of light probes is to provide high quality lighting (including indirect bounced light) on moving objects in your scene. The secondary use of light probes is to provide the lighting information for static scenery when that scenery is using Unity’s LOD system.
What is L and M in spherical harmonics?
The indices ℓ and m indicate degree and order of the function. The spherical harmonic functions can be used to describe a function of θ and φ in the form of a linear expansion. Completeness implies that this expansion converges to an exact result for sufficient terms.
How are light probes related to spherical harmonics?
Now that you understand the basic operations and properties of SH, we can think how to apply them to GI. A light probe records how much light is coming from every direction to the point where the probe is located. This is a 2D function on a sphere and can be represented as SH (or 3 SH function for red, green and blue).
What kind of lighting is spherical harmonic lighting?
Spherical harmonic (SH) lighting is a family of real-time rendering techniques that can produce highly realistic shading and shadowing with comparatively little overhead. All SH lighting techniques involve replacing parts of standard lighting equations with spherical functions that have been projected…
How are spherical harmonics used to represent 2D functions?
Spherical Harmonics is a way to represent a 2D function on a surface of a sphere. Instead of spatial domain (like cubemap), SH is defined in frequency domain with some interesting properties and operations relevant to lighting that can be performed efficiently.
Which is the best order for light probes?
For light probes that are used only for Lambertian diffuse lighting, quite low-order SH is sufficient since the convolution is performed with cosine-lobe, which can be represented with order-2 SH (9 coefficients).