import graph3; import palette; size(12cm,IgnoreAspect); currentprojection=orthographic(1,-2,1); real X=4.5; real M=abs(gamma((X,0))); pair Gamma(pair z) { return (z.x > 0 || z != floor(z.x)) ? gamma(z) : M; } real f(pair z) {return min(abs(Gamma(z)),M);} surface s=surface(f,(-2.1,-2),(X,2),70,Spline); real Arg(triple v) { return degrees(Gamma((v.x,v.y)),warn=false); } s.colors(palette(s.map(Arg),Wheel())); draw(s); real xmin=point((-1,-1,-1)).x; real xmax=point((1,1,1)).x; draw((xmin,0,0)--(xmax,0,0),dashed); xaxis3("$\mathop{\rm Re} z$",Bounds,InTicks); yaxis3("$\mathop{\rm Im} z$",Bounds,InTicks(beginlabel=false)); zaxis3("$|\Gamma(z)|$",Bounds,InTicks);