program threedeeplot;
const w = 640;
      h = 400;

var u0,v0:integer;

function fun(x0,y0:real):real;
const vscale = 50.0;
      hscale = 20.0;

var x,y,f:real;
begin
	x := x0 / hscale;
	y := y0 / hscale;
	f := sin(sqrt(x*x + y*y));

	fun := f * vscale;
end;

procedure plot;
var maxV,minV:array [0..w] of real;
    shift:integer;
    x,y,z:integer;
    lastZ:integer;
    numLines:integer;
    i:integer;
    u,v,lastU,lastV:integer;
    color:integer;

  procedure resetCurve;
  begin
  	lastU := -1;
  	lastV := -1;
  end;

begin
	for i := 0 to w do
	begin
		maxV[i] := -10000;
		minV[i] :=  10000;
	end;

	color := 1;
	shift := 4;
	x := 0;
	numLines := 80;
	u0 := w div 2;
	v0 := h div 2;

	for i := -(numLines div 2) to numLines do
	begin
		resetCurve;
		x := i * (w div numLines);
		for y := -w to w do
		begin
			z := round(fun(x,y));
			u := round(y + u0 + i * shift);
			v := round(-z + v0 - i * shift);

			if (u >= 0) and (u < w) then
			begin
				if (v < maxV[u]) and (v > minV[u]) then
					resetCurve
				else
				begin	
					if (u >= 0) and (u < w) and (v > maxV[u]) then
						maxV[u] := v;
					if (u >= 0) and (u < w) and (v < minV[u]) then
						minV[u] := v;

					if lastZ < z then
						color := 8
					else
						color := 1;

					if (u >= w) or (u < 0) or (v >= h) or (v < 0) then
						resetCurve
					else
					begin				
						if lastU = -1 then
							putpixel(u,v,color)
						else
							drawline(lastU,lastV,u,v,color);
					end;
					lastU := u;
					lastV := v;
					lastZ := z;
				end;
			end;
		end;
	end;
end;

begin
	initgraphics;
	plot;
end.