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#pragma once
static inline void SHEvalDirection9 (float x, float y, float z, float outsh[9])
{
// Core i7 920, VS2008 Release, FPU code:
// 114 clocks
//D3DXSHEvalDirection (outsh, 3, &D3DXVECTOR3(x,y,z));
/*
// 314 clocks
// Reference implementation from Stupid Spherical Harmonics Tricks
// http://www.ppsloan.org/publications/StupidSH36.pdf
const float kSqrtPI = sqrtf(kPI);
const float kSqrt3 = sqrtf(3.0f);
const float kSqrt15 = sqrtf(15.0f);
outsh[0] = 1.0f / (2.0f * kSqrtPI);
outsh[1] = -(kSqrt3 * y) / (2.0f * kSqrtPI);
outsh[2] = (kSqrt3 * z) / (2.0f * kSqrtPI);
outsh[3] = -(kSqrt3 * x) / (2.0f * kSqrtPI);
outsh[4] = (kSqrt15 * x * y) / (2.0f * kSqrtPI);
outsh[5] = -(kSqrt15 * y * z) / (2.0f * kSqrtPI);
outsh[6] = (sqrtf(5.0f) * (3.0f*z*z-1.0f)) / (4.0f * kSqrtPI);
outsh[7] = -(kSqrt15 * x * z) / (2.0f * kSqrtPI);
outsh[8] = (kSqrt15 * (x*x - y*y)) / (4.0f * kSqrtPI);
*/
// 86 clocks
// Make sure all constants are never computed at runtime
const float kInv2SqrtPI = 0.28209479177387814347403972578039f; // 1 / (2*sqrt(kPI))
const float kSqrt3Div2SqrtPI = 0.48860251190291992158638462283835f; // sqrt(3) / (2*sqrt(kPI))
const float kSqrt15Div2SqrtPI = 1.0925484305920790705433857058027f; // sqrt(15) / (2*sqrt(kPI))
const float k3Sqrt5Div4SqrtPI = 0.94617469575756001809268107088713f; // 3 * sqrtf(5) / (4*sqrt(kPI))
const float kSqrt15Div4SqrtPI = 0.54627421529603953527169285290135f; // sqrt(15) / (4*sqrt(kPI))
const float kOneThird = 0.3333333333333333333333f; // 1.0/3.0
outsh[0] = kInv2SqrtPI;
outsh[1] = - y * kSqrt3Div2SqrtPI;
outsh[2] = z * kSqrt3Div2SqrtPI;
outsh[3] = - x * kSqrt3Div2SqrtPI;
outsh[4] = x * y * kSqrt15Div2SqrtPI;
outsh[5] = - y * z * kSqrt15Div2SqrtPI;
outsh[6] = (z*z-kOneThird) * k3Sqrt5Div4SqrtPI;
outsh[7] = - x * z * kSqrt15Div2SqrtPI;
outsh[8] = (x*x-y*y) * kSqrt15Div4SqrtPI;
}
static inline void SHEvalDirectionalLight9 (
float x, float y, float z,
float colorR, float colorG, float colorB,
float outR[9], float outG[9], float outB[9])
{
// Core i7 920, VS2008 Release, FPU code:
// 397 clocks
//D3DXSHEvalDirectionalLight (3, &D3DXVECTOR3(x,y,z), colorR, colorG, colorB, outR, outG, outB);
// 300 clocks
float sh[9];
SHEvalDirection9 (x, y, z, sh);
// Normalization factor from http://www.ppsloan.org/publications/StupidSH36.pdf
const float kNormalization = 2.9567930857315701067858823529412f; // 16*kPI/17
float rscale = colorR * kNormalization;
float gscale = colorG * kNormalization;
float bscale = colorB * kNormalization;
for (int i = 0; i < 9; ++i)
{
float c = sh[i];
outR[i] = c * rscale;
outG[i] = c * gscale;
outB[i] = c * bscale;
}
}
// Add 'out' to the 0th SH coefficients
static inline void SHEvalAmbientLight(const ColorRGBAf& ambient, float out[3])
{
const float k2SqrtPI = 3.54490770181103205459633496668229f; // 2*sqrt(kPI)
out[0] = ambient.r * k2SqrtPI;
out[1] = ambient.g * k2SqrtPI;
out[2] = ambient.b * k2SqrtPI;
}
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