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{ RCSid $Id$ } |
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{ Ward-Geisler-Moroder-Duer anisotropic BSDF model } |
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{ Final 5 real arguments are alpha_x and alpha_y roughnesses and Up vector } |
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ax = arg(AC-4); { ax is roughness in Up orientation } |
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ay = arg(AC-3); |
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Up(i) = arg(AC-3+i); { up vector does not need to be normalized } |
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Vux = cross(1,Up,N); |
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Vuy = cross(2,Up,N); |
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Vuz = cross(3,Up,N); |
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vnorm = 1/sqrt(Vux*Vux + Vuy*Vuy + Vuz*Vuz); |
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Vnx = Vux*vnorm; |
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Vny = Vuy*vnorm; |
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Vnz = Vuz*vnorm; |
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Vn(i) = select(i, Vnx, Vny, Vnz); |
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Unx = cross(1,N,Vn); |
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Uny = cross(2,N,Vn); |
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Unz = cross(3,N,Vn); |
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{ Transform vectors, normalized (dx,dy,dz) away from surf } |
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surf_dx(dx,dy,dz) = dx*Unx + dy*Uny + dz*Unz; |
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surf_dy(dx,dy,dz) = dx*Vnx + dy*Vny + dz*Vnz; |
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surf_dz(dx,dy,dz) = dx*Nx + dy*Ny + dz*Nz; |
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inc_dx = surf_dx(-Dx,-Dy,-Dz); |
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inc_dy = surf_dy(-Dx,-Dy,-Dz); |
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inc_dz = Rdot; |
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arefl(hx,hy,hz) = exp(-(hx*hx/(ax*ax) + hy*hy/(ay*ay))/(hz*hz)) * |
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(hx*hx + hy*hy + hz*hz) / |
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(PI*ax*ay*hz*hz*hz*hz); |
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axmit(hx,hy,hz) = exp(-(hx*hx/(ax*ax) + hy*hy/(ay*ay))/(hz*hz)) / |
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(4*PI*ax*ay); |
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dobsdf(sdx,sdy,sdz) = if(sdz, arefl(inc_dx+sdx, inc_dy+sdy, inc_dz+sdz), |
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axmit(inc_dx+sdx, inc_dy+sdy, inc_dz-sdz) / sqrt(-sdz*inc_dz) ); |
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absdf(ox,oy,oz) = dobsdf(surf_dx(ox,oy,oz), surf_dy(ox,oy,oz), surf_dz(ox,oy,oz)); |
