k3d/share/shaders/k3d_orennayar.sl:17: *   sigma - roughness (0 is lambertian, larger values are rougher)
k3d/share/shaders/k3d_orennayar.sl:43:	   float sigma = 0.0; )
k3d/share/shaders/k3d_orennayar.sl:50:    float alpha, beta, sigma2, cos_phi_diff;
k3d/share/shaders/k3d_orennayar.sl:56:    sigma2 = sigma*sigma;
k3d/share/shaders/k3d_orennayar.sl:65:	C1 = 1 - 0.5 * sigma2/(sigma2+0.33);
k3d/share/shaders/k3d_orennayar.sl:66:	C2 = 0.45 * sigma2 / (sigma2 + 0.09);
k3d/share/shaders/k3d_orennayar.sl:70:	C3 = 0.125 * sigma2 / (sigma2+0.09) * pow ((4*alpha*beta)/(PI*PI),2);
k3d/share/shaders/k3d_orennayar.sl:73:	L2 = (Cs * Cs) * (0.17 * cos_theta_i * sigma2/(sigma2+0.13) *
k3d/share/shaders/k3d_smoke2.sl:97:  float d, sigma, tau;
