The lighting information in the light probesLight probes store information about how light passes through space in your scene. A collection of light probes arranged within a given space can improve lighting on moving objects and static LOD scenery within that space. More info
See in Glossary are encoded as Spherical Harmonics basis functions. We use third order polynomials, also known as L2 Spherical Harmonics. These are stored using 27 floating point values, 9 for each color channel.
The EnlightenA lighting system by Geomerics used in Unity for lightmapping and for Enlighten Realtime Global Illumination. More info
See in Glossary Global IlluminationA group of techniques that model both direct and indirect lighting to provide realistic lighting results.
See in Glossary implementation in Unity uses a different spherical harmonics approach than Geomerics, the feature’s original developer, namely the notation and reconstruction method from Peter-Pike Sloan’s paper, Stupid Spherical Harmonics (SH) Tricks. Geomerics’ original approach was based on the notation and reconstruction method from Ramamoorthi/Hanrahan’s paper, An Efficient Representation for Irradiance Environment Maps.
The shaderA program that runs on the GPU. More info
See in Glossary code for reconstruction is found in UnityCG.cginc and is using the method from Appendix A10 Shader/CPU code for Irradiance Environment Maps from Peter-Pikes paper.
The data is internally ordered like this:
[L00: DC]
[L1-1: y] [L10: z] [L11: x]
[L2-2: xy] [L2-1: yz] [L20: zz] [L21: xz] [L22: xx - yy]
The 9 coefficients for R, G and B are ordered like this:
L00, L1-1, L10, L11, L2-2, L2-1, L20, L21, L22, // red channel
L00, L1-1, L10, L11, L2-2, L2-1, L20, L21, L22, // blue channel
L00, L1-1, L10, L11, L2-2, L2-1, L20, L21, L22 // green channel
For more “under-the-hood” information about Unity’s light probe system, you can read Robert Cupisz’s talk from GDC 2012, Light Probe Interpolation Using Tetrahedral Tessellations”, GDC 2012
2017–06–08 Page published
Light Probes updated in 5.6