Transcript Drawing Primitives

Drawing Primitives
Foreward
 This presentation shows how some primitive shapes
may be drawn using openTK (openGL)
 This is not the only approach to draw these
primitives, but may be the most common
DrawLine()
private void DrawLine()
{ // Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.Begin(BeginMode.Lines);
GL.Vertex3(20.0, 20.0, 0.0);
GL.Vertex3(80.0, 20.0, 0.0);
GL.Vertex3(80.0, 80.0, 0.0);
GL.Vertex3(20.0, 80.0, 0.0);
GL.End();
// Flush created objects to the screen, i.e., force rendering.
glControl1.SwapBuffers();
}
Lines
Polygon
private void DrawPolygon()
{ // Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.Begin(BeginMode.Polygon);
GL.Vertex3(20.0, 20.0, 0.0);
GL.Vertex3(80.0, 20.0, 0.0);
GL.Vertex3(80.0, 80.0, 0.0);
GL.Vertex3(20.0, 80.0, 0.0);
GL.End();
// force rendering.
glControl1.SwapBuffers();
}
Polygon
Triangles
private void DrawLine()
{ // Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.Begin(BeginMode.Triangles);
GL.Vertex3(10.0, 90.0, 0.0);
GL.Vertex3(10.0, 10.0, 0.0);
GL.Vertex3(35.0, 75.0, 0.0);
GL.Vertex3(30.0, 20.0, 0.0);
GL.Vertex3(90.0, 90.0, 0.0);
GL.Vertex3(80.0, 40.0, 0.0);
GL.End();
// force rendering.
glControl1.SwapBuffers();
}
Triangles
LineStrip
private void DrawLineStrip()
{ // Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.Begin(BeginMode.LineStrip);
GL.Vertex3(20.0, 20.0, 0.0);
GL.Vertex3(80.0, 20.0, 0.0);
GL.Vertex3(80.0, 80.0, 0.0);
GL.Vertex3(20.0, 80.0, 0.0);
GL.End();
// force rendering.
glControl1.SwapBuffers();
}
LineStrip
TriangleFan
private void DrawTRFan()
{
// Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.PolygonMode(MaterialFace.FrontAndBack, PolygonMode.Line);
// Draw a polygon with specified vertices.
GL.Begin(BeginMode.TriangleFan);
GL.Vertex3(10.0, 10.0, 0.0);
GL.Vertex3(15.0, 90.0, 0.0);
GL.Vertex3(55.0, 75.0, 0.0);
GL.Vertex3(80.0, 30.0, 0.0);
GL.Vertex3(90.0, 10.0, 0.0);
GL.End();
// Flush created objects to the screen, i.e., force rendering.
glControl1.SwapBuffers();
}
Triangle Fan
QuadStrip
private void DrawQDStrip()
{
// Clear screen to background color.
GL.Clear(ClearBufferMask.ColorBufferBit);
// Set foreground (or drawing) color.
GL.Color3(Color.White);
GL.PolygonMode(MaterialFace.FrontAndBack, PolygonMode.Line);
// Draw a polygon with specified vertices.
GL.Begin(BeginMode.QuadStrip);
// glBegin(GL_LINE_STRIP);
// glBegin(GL_LINE_LOOP);
GL.Vertex3(10.0, 90.0, 0.0);
GL.Vertex3(10.0, 10.0, 0.0);
GL.Vertex3(30.0, 80.0, 0.0);
GL.Vertex3(40.0, 15.0, 0.0);
GL.Vertex3(60.0, 75.0, 0.0);
GL.Vertex3(60.0, 25.0, 0.0);
GL.Vertex3(90.0, 90.0, 0.0);
GL.Vertex3(80.0, 20.0, 0.0);
GL.End();
// Flush created objects to the screen, i.e., force rendering.
glControl1.SwapBuffers();
}
QuadStrip
Constructing Shapes from Lines
Shapes From Lines
Composing Solid Objects Using TRFans
A Cone
Same Cone Using Outline Mode