{ RCSid $Id: klems_half.cal,v 1.5 2022/07/14 02:52:02 greg Exp $ } { Compute interior bin for half Klems BSDF basis (0-72) Returns -1 for wrong-side rays Modified from klems_full.cal 7/18/2014 G. Ward } DEGREE : PI/180; Acos(x) : if(x-1, 0, if(-1-x, PI, acos(x))) / DEGREE; posangle(a) : if(-a, a + 2*PI, a) / DEGREE; Atan2(y,x) : posangle(atan2(y,x)); khpola(r) : select(r, 6.5, 19.5, 32.5, 45.5, 58.5, 71.5, 90); khnaz(r) : select(r, 1, 8, 12, 16, 20, 12, 8); khaccum(r) : if(r-.5, khnaz(r) + khaccum(r-1), 0); khfindrow(r, pol) : if(r-khpola(0)+.5, r, if(pol-khpola(r), khfindrow(r+1, pol), r) ); khazn(azi,inc) : if((360-.5*inc)-azi, floor((azi+.5*inc)/inc), 0); khbin2(pol,azi) = if(pol-90, -1, select(khfindrow(1, pol), khazn(azi,360/khnaz(1)), khaccum(1) + khazn(azi,360/khnaz(2)), khaccum(2) + khazn(azi,360/khnaz(3)), khaccum(3) + khazn(azi,360/khnaz(4)), khaccum(4) + khazn(azi,360/khnaz(5)), khaccum(5) + khazn(azi,360/khnaz(6)), khaccum(6) + khazn(azi,360/khnaz(7)) ) ); RHS = 1; { set to -1 for left-handed system } khbin(Nx,Ny,Nz,Ux,Uy,Uz) = khbin2(Acos(-Dx*Nx-Dy*Ny-Dz*Nz), Atan2(-Dx*Ux-Dy*Uy-Dz*Uz + (Nx*Dx+Ny*Dy+Nz*Dz)*(Nx*Ux+Ny*Uy+Nz*Uz), -RHS*(Dx*(Uy*Nz-Uz*Ny) + Dy*(Uz*Nx-Ux*Nz) + Dz*(Ux*Ny-Uy*Nx)))); Nkhbins : khaccum(khnaz(0)); { Number of bins for one elevation }