Как нарисовать конус на основе круга:

//круг
PaintBox3->Repaint(); 
           PaintBox3->Canvas->Brush->Color = RGB(random(255),random(255),random(255));
      PaintBox3->Canvas->Ellipse (c1.x-c1.y+300, 150-(c1.y- c1.r), c1.x+ c1.r+300, 150-(c1.y+c1.y));

TForm1 *Form1;
 
struct TPoint {
  int x,y,r;
};
// ...
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  ::TPoint c1;
  c1.x = StrToInt(Edit1->Text);
  c1.y = StrToInt(Edit2->Text);
  c1.r = StrToInt(Edit3->Text);
//круг
  PaintBox1->Repaint();
  randomize();
  PaintBox1->Canvas->Brush->Color = RGB(random(255),
                                        random(255),
                                        random(255));
  PaintBox1->Canvas->Ellipse(c1.x-c1.y+300,
                             150-(c1.y-c1.r),
                             c1.x+ c1.r+300,
                             150-(c1.y+c1.y));
}
//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
struct TPoint {int x,y,r;};
void __fastcall TForm1::PaintBox1Paint(TObject *Sender)
{
  ::TPoint c1;
  Types::TPoint points[4];
  int t[8] = {350,20,249,85,396,92,350,20};
  c1.x = StrToInt(Edit1->Text);
  c1.y = StrToInt(Edit2->Text);
  c1.r = StrToInt(Edit3->Text);
  points[0]=Point(t[0],t[1]);
  points[1]=Point(t[2],t[3]);
  points[2]=Point(t[4],t[5]);
  points[3]=Point(t[6],t[7]);
  PaintBox1->Repaint();
  randomize();
  PaintBox1->Canvas->Brush->Color = RGB(random(255),
                                        random(255),
                                        random(255));
  PaintBox1->Canvas->Polygon(points,3);
  PaintBox1->Canvas->Brush->Color = RGB(random(255),
                                        random(255),
                                        random(255));
  PaintBox1->Canvas->Ellipse(c1.x-c1.y+200,
                             150-(c1.y-c1.r),
                             c1.x+ c1.r+300,
                             150-(c1.y+c1.y));
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  PaintBox1Paint(Sender);
}
//---------------------------------------------------------------------------