Create Canvas 3D-Diagram

const
  Colors: array[0..10] of TColor = (clRed, clGreen, clBlue, clYellow,
                                     clMaroon, clTeal, clNavy, clOlive,
                                     clPurple, clLime, clFuchsia);
                                     
//

function Min(a,b: Integer): LongInt;
begin
  if a<=b then result:=a else result:=b;
end;

function Max(a,b: Integer): LongInt;
begin
  if a>b then result:=a else result:=b;
end;

function GetArcPoint(cPoint: TPoint; radius, angle: Extended): TPoint;
begin
  result.x:=Round(cPoint.x + radius * Cos(angle * 2 * pi / 360));
  result.y:=Round(cPoint.y - radius * Sin(angle * 2 * pi / 360));
end;

function GetCentrePoint(oRect: TRect): TPoint;
begin
  result.x:=oRect.left + (oRect.right-oRect.left) div 2;
  result.y:=oRect.top + (oRect.bottom-oRect.top) div 2;
end;

procedure TForm1.FormPaint(Sender: TObject);
var cv, vv, za, va, co, sum, radius, angle, valuecount, valuesum: Integer; 
    middlepoint, copypoint: TPoint; 
    values, angles: array[0..10] of Integer; 
    CirclePoints: array[0..365] of TPoint;
begin 
  values[0]:=15;
  values[1]:=25;
  values[2]:=20;
  values[3]:=15;
  values[4]:=15;
  valuecount:=5;
  valuesum:=0; for cv:=0 to valuecount-1 do valuesum:=valuesum+values[cv];
  Canvas.Brush.Color:=clWhite;
  Canvas.FillRect(ClientRect);
  Canvas.Pen.Color:=clBlack;
  radius:=(Min(width, height)-40) div 2;
  middlepoint:=GetCentrePoint(ClientRect);

  //Werte in Winkel konv.
  for cv:=0 to valuecount-1 do
   angles[cv]:=Round(values[cv]*360/valuesum); 

   //Tortenrand ausgeben
  za:=0; sum:=angles[0]; va:=1; co:=0;
  for angle:=0 to 360 do
  begin
   if angle<180 then 
   begin 
    if angle=sum then begin inc(co); sum:=sum+angles[va]; inc(va); end; 
    Continue;
   end; 

   CirclePoints[za]:=GetArcPoint(middlepoint, radius, angle); 
   CirclePoints[za].y:=middlepoint.y-(middlepoint.y-CirclePoints[za].y) div 2 + radius div 5; //Tortenhoehe 20% des Radius 

   if (angle=sum) or (angle=360) then 
   begin 
      Canvas.Brush.Color:=Colors[co]; inc(co);

      copypoint:=CirclePoints[za]; 
      CirclePoints[za+1].x:=CirclePoints[za].x; 
      CirclePoints[za+1].y:=middlepoint.y; 
      CirclePoints[za+2].x:=CirclePoints[0].x; 
      CirclePoints[za+2].y:=middlepoint.y; 
      Polygon(Canvas.Handle, CirclePoints[0], za+3); 
      CirclePoints[0]:=copypoint;
      sum:=sum+angles[va]; inc(va);
      za:=1; 
      Continue; 
   end;
   inc(za); 
  end;

  //obere Tortenfläche ausgeben
  za:=0; sum:=angles[0]; va:=1; co:=0;
  for angle:=0 to 360 do
  begin
   CirclePoints[za]:=GetArcPoint(middlepoint, radius, angle); 
   CirclePoints[za].y:=middlepoint.y-(middlepoint.y-CirclePoints[za].y) div 2; 

   if (angle=sum) or (angle=360) then 
   begin
      Canvas.Brush.Color:=Colors[co]; inc(co);
      copypoint:=CirclePoints[za]; 
      CirclePoints[za+1]:=middlepoint; 
      Polygon(Canvas.Handle, CirclePoints[0], za+2); 
      CirclePoints[0]:=copypoint;
      sum:=sum+angles[va]; inc(va);
      za:=1; 
      Continue;
   end;
   inc(za);
 end;
end;