Geek asks and answers

How to draw a triangle using OpenTK?

I am not sure why this code does not just draw a triangle on the screen (spelling). I use OpenTK 1.1, as well as OpenGL 1.1.

List<Vector3> simpleVertices = new List<Vector3>();
simpleVertices.Add(new Vector3(0,0,0));
simpleVertices.Add(new Vector3(100,0,0));
simpleVertices.Add(new Vector3(100,100,0));

GL.MatrixMode(All.Projection);
GL.LoadIdentity();

GL.MatrixMode(All.Projection);
GL.Ortho(0, 480, 320, 0,0,1000);

GL.MatrixMode(All.Modelview);
GL.LoadIdentity();
GL.Translate(0,0,10);
unsafe
{
  Vector3* data = (Vector3*)Marshal.AllocHGlobal(
                        Marshal.SizeOf(typeof(Vector3)) * simpleVertices.Count);

  for(int i = 0; i < simpleVertices.Count; i++)
  {
    ((Vector3*)data)[i] = simpleVertices[i];
  }

  GL.VertexPointer(3, All.Float, sizeof(Vector3), new IntPtr(data));
  GL.DrawArrays(All.Triangles, 0, simpleVertices.Count);
}

The code is executed once in each update cycle in the drawing function. What I think I am doing (but apparently not) creates a set of position vertices to form a triangle and draw it 10 units in front of the camera.

Why doesn't this code draw a triangle?

+3
source share
1 answer

In OpenGL, the Z axis points to the screen, so when you write

GL.Translate(0,0,10);

he actually translates it “in front” to the screen.

GL.Ortho 0,1000. , 0 1000 MINUS Z (= ).

, GL.Translate(0,0,-10); , GL.Translate(0,0,10); .

+1

More articles:


All Articles