LightProbeUtility.cs

    //Original code from:
    //https://github.com/RishiAstra/Survive-From-Scratch/blob/21d98a4dcbb3ef25a79bb3ca9733b35b866eda74/Assets/AwesomeTechnologies/VegetationStudio/Utility/LightProbeUtility.cs
    //Added EvaluateSH2 method to evaluate the SH2 with C#, so it will work with Unity Jobs
    public class LightProbeUtility
    {
        public struct LightProbeData
        {
            public Vector4 unity_SHAr;
            public Vector4 unity_SHAg;
            public Vector4 unity_SHAb;
            public Vector4 unity_SHBr;
            public Vector4 unity_SHBg;
            public Vector4 unity_SHBb;
            public Vector4 unity_SHC;
        }

        public static LightProbeData GetLightProbeData(SphericalHarmonicsL2 sh)
        {
            return new LightProbeData
            {
                unity_SHAr = Get_Unity_SHAr(sh),
                unity_SHAg = Get_unity_SHAg(sh),
                unity_SHAb = Get_unity_SHAb(sh),
                unity_SHBr = Get_Unity_SHBr(sh),
                unity_SHBg = Get_Unity_SHBg(sh),
                unity_SHBb = Get_Unity_SHBb(sh),
                unity_SHC = Get_Unity_SHC(sh)
            };
        }
        
        public static Vector4 Get_Unity_SHAr(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[0, 3], sh[0, 1], sh[0, 2], sh[0, 0] - sh[0, 6]);
        }

        public static Vector4 Get_unity_SHAg(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[1, 3], sh[1, 1], sh[1, 2], sh[1, 0] - sh[1, 6]);
        }

        public static Vector4 Get_unity_SHAb(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[2, 3], sh[2, 1], sh[2, 2], sh[2, 0] - sh[2, 6]);
        }

        public static Vector4 Get_Unity_SHBr(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[0, 4], sh[0, 5], sh[0, 6] * 3, sh[0, 7]);
        }

        public static Vector4 Get_Unity_SHBg(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[1, 4], sh[1, 5], sh[1, 6] * 3, sh[1, 7]);
        }

        public static Vector4 Get_Unity_SHBb(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[2, 4], sh[2, 5], sh[2, 6] * 3, sh[2, 7]);
        }

        public static Vector4 Get_Unity_SHC(SphericalHarmonicsL2 sh)
        {
            return new Vector4(sh[0, 8], sh[2, 8], sh[1, 8], 1);
        }

        // normal should be normalized, w=1.0
        private static Vector3 SHEvalLinearL0L1(Vector4 normal, LightProbeData lightProbeData)
        {
            Vector3 x;

            // Linear (L1) + constant (L0) polynomial terms
            x.x = Vector4.Dot(lightProbeData.unity_SHAr, normal);
            x.y = Vector4.Dot(lightProbeData.unity_SHAg, normal);
            x.z = Vector4.Dot(lightProbeData.unity_SHAb, normal);

            return x;
        }

        // normal should be normalized, w=1.0
        private static Vector3 SHEvalLinearL2(Vector4 normal, LightProbeData lightProbeData)
        {
            Vector3 x1, x2;
            // 4 of the quadratic (L2) polynomials
            Vector4 vB;
            vB.x = normal.x * normal.y;
            vB.y = normal.y * normal.z;
            vB.z = normal.z * normal.z;
            vB.w = normal.z * normal.x;

            x1.x = Vector4.Dot(lightProbeData.unity_SHBr, vB);
            x1.y = Vector4.Dot(lightProbeData.unity_SHBg, vB);
            x1.z = Vector4.Dot(lightProbeData.unity_SHBb, vB);

            // Final (5th) quadratic (L2) polynomial
            float vC = normal.x * normal.x - normal.y * normal.y;
            x2 = lightProbeData.unity_SHC * vC;

            return x1 + x2;
        }

        // normal should be normalized, w=1.0
        // output in active color space
        private static Vector3 ShadeSH9(Vector4 normal, LightProbeData lightProbeData)
        {
            // Linear + constant polynomial terms
            Vector3 res = SHEvalLinearL0L1(normal, lightProbeData);

            // Quadratic polynomials
            res += SHEvalLinearL2(normal, lightProbeData);

            //todo: ?
            //# ifdef UNITY_COLORSPACE_GAMMA
            //            res = LinearToGammaSpace(res);
            //#endif
            return res;
        }

        public static Color EvaluateSH2(SphericalHarmonicsL2 sh2, Vector3 normal)
        {
            var lightProbeData = LightProbeUtility.GetLightProbeData(sh2);
            var vector = ShadeSH9(new Vector4(normal.x, normal.y, normal.z, 1.0f), lightProbeData);
            return new Color(vector.x, vector.y, vector.z, 1.0f);
        }
    }