Chapter 774: SphericalHarmonics3

Core Idea

Represents a third-order spherical harmonics (SH). Light probes use this class to encode lighting information.

• Primary reference: https://graphics.stanford.edu/papers/envmap/envmap.pdf
• Secondary reference: https://www.ppsloan.org/publications/StupidSH36.pdf

Key Concepts

• coefficients : Array.<Vector3>: An array holding the (9) SH coefficients.
• isSphericalHarmonics3 : boolean (readonly): This flag can be used for type testing.

Reference Tables

Constructor

Signature
new SphericalHarmonics3()

Properties

Property	Description
.coefficients : Array.<Vector3>	An array holding the (9) SH coefficients.
.isSphericalHarmonics3 : boolean (readonly)	This flag can be used for type testing.

Methods

Method	Description
.add( sh : SphericalHarmonics3 ) : SphericalHarmonics3	Adds the given SH to this instance.
.addScaledSH( sh : SphericalHarmonics3, s : number ) : SphericalHarmonics3	A convenience method for performing SphericalHarmonics3#add and SphericalHarmonics3#scale at once.
.clone() : SphericalHarmonics3	Returns a new spherical harmonics with copied values from this instance.
.copy( sh : SphericalHarmonics3 ) : SphericalHarmonics3	Copies the values of the given spherical harmonics to this instance.
.equals( sh : SphericalHarmonics3 ) : boolean	Returns true if this spherical harmonics is equal with the given one.
.fromArray( array : Array.<number>, offset : number ) : SphericalHarmonics3	Sets the SH coefficients of this instance from the given array.
.getAt( normal : Vector3, target : Vector3 ) : Vector3	Returns the radiance in the direction of the given normal.
.getIrradianceAt( normal : Vector3, target : Vector3 ) : Vector3	Returns the irradiance (radiance convolved with cosine lobe) in the direction of the given normal.
.lerp( sh : SphericalHarmonics3, alpha : number ) : SphericalHarmonics3	Linear interpolates between the given SH and this instance by the given alpha factor.
.scale( s : number ) : SphericalHarmonics3	Scales this SH by the given scale factor.
.set( coefficients : Array.<Vector3> ) : SphericalHarmonics3	Sets the given SH coefficients to this instance by copying the values.
.toArray( array : Array.<number>, offset : number ) : Array.<number>	Returns an array with the SH coefficients, or copies them into the provided array. The coefficients are represented as numbers.
.zero() : SphericalHarmonics3	Sets all SH coefficients to 0.

Key Takeaways

1. Most relevant properties: coefficients, isSphericalHarmonics3.
2. Key methods: add, addScaledSH, clone, copy.

Connects To

• Source: src/math/SphericalHarmonics3.js