Question

How do I draw a cylinder with OpenGL in OpenTK?

Answer 1

Sample code from an older project of mine. This creates an “uncapped” cylinder (top and bottom are empty).

int segments = 10; // Higher numbers improve quality 
int radius = 3;    // The radius (width) of the cylinder
int height = 10;   // The height of the cylinder

var vertices = new List<Vector3>();
for (double y = 0; y < 2; y++)
{
    for (double x = 0; x < segments; x++)  
    {
        double theta = (x / (segments - 1)) * 2 * Math.PI;

        vertices.Add(new Vector3()
        {
            X = (float)(radius * Math.Cos(theta)),
            Y = (float)(height * y),
            Z = (float)(radius * Math.Sin(theta)),
        });
    }
}

var indices = new List<int>();
for (int x = 0; x < segments - 1; x++)
{
    indices.Add(x);
    indices.Add(x + segments);
    indices.Add(X + segments + 1);

    indices.Add(x + segments + 1);
    indices.Add(x + 1);
    indices.Add(x);
}

You can now render the cylinder like this:

GL.Begin(BeginMode.Triangles);
foreach (int index in indices)
    GL.Vertex3(vertices[index]);
GL.End();

You can also upload vertices and indices into a vertex buffer object to improve performance.