prologues := 3;  u=18mm; textscale=u/12mm;  def cone =   begingroup;   save pmax,dmax,persp,persp_nt,tens,arr;   save harr,rarr;   save p,d;   save axisprotrusion;   save xax,yax,zax;   save height,width,heightu,widthu;   pmax = 2; dmax = 0;   persp_nt = 0.5;   tens = 2-persp_nt;   persp = persp_nt*u;   arr = 0.3u; % how far to offset the arrows from the diagram   axisprotrusion = 0.4u;  % how far do the axes protrude?   pair harr[],rarr[]; % endpoints for arrows   path p[],d[]; % just plain paths for now   pair xax[],yax[],zax[]; % x,y,z are taken; these are for the axes   % parameters for the actual cone   height = 1;   width = 1.5;   heightu = height*u;   widthu = width*u;   % solid paths   p0 = (0,0)--(widthu/2,heightu);   p1 = (0,0)--(-widthu/2,heightu);   p2 = fullcircle scaled u xscaled width yscaled persp_nt shifted (0,heightu);   % dotted paths   % don't draw this; it's reference for the y-axis   d99 = halfcircle scaled u xscaled 2 yscaled (2*persp_nt) rotated 180;   % endpoints of dimension arrows   harr0 = (widthu/2,0);   harr1 = (widthu/2,heightu);   rarr0 = (0,heightu);   rarr1 = (widthu/2,heightu);    % actually draw   pickup pencircle scaled 1pt;   for i=0 upto pmax:     draw p[i];   endfor;   drawdblarrow (harr0..harr1);   label.rt(btex $h$ etex scaled textscale,.5[harr0,harr1]);   drawdblarrow (rarr0..rarr1);   label.top(btex $r$ etex scaled textscale,.3[rarr0,rarr1]);   % x axis   xax0 = (0,0);   xax1 = (widthu/2+arr,0);   drawarrow (xax0..xax1);   label.rt(btex $x$ etex scaled textscale,xax1);   % y axis   yax0 = (0,0);   yax1 = point 1 of d99;   yax2 = (width*persp_nt)[yax0,yax1];   drawarrow (yax0..yax2);   label.bot(btex $y$ etex scaled textscale,yax2);   % z axis   zax0 = (0,0);   zax1 = (0,heightu);   zax2 = (0,heightu+axisprotrusion);   drawarrow (zax1..zax2);   draw zax0..zax1 dashed evenly;   label.top(btex $z$ etex scaled textscale,zax2);   endgroup; enddef;  beginfig(1)   cone;   currentpicture := currentpicture shifted (100,100); % avoid unwanted clipping endfig; end