/// <summary>
/// Adds a surface of revolution.
/// </summary>
/// <param name="points">
/// The points (y coordinates are radius, x coordinates are distance from the origin along the axis of revolution)
/// </param>
/// <param name="origin">
/// The origin of the revolution axis.
/// </param>
/// <param name="direction">
/// The direction of the revolution axis.
/// </param>
/// <param name="thetaDiv">
/// The number of divisions around the mesh.
/// </param>
/// <remarks>
/// See http://en.wikipedia.org/wiki/Surface_of_revolution.
/// </remarks>
public void AddRevolvedGeometry(IList<Point> points, Point3D origin, Vector3D direction, int thetaDiv)
{
direction.Normalize();
// Find two unit vectors orthogonal to the specified direction
var u = direction.FindAnyPerpendicular();
var v = Vector3D.Cross(direction, u);
u.Normalize();
v.Normalize();
var circle = GetCircle(thetaDiv);
int index0 = this.positions.Count;
int n = points.Count;
int totalNodes = (points.Count - 1) * 2 * thetaDiv;
int rowNodes = (points.Count - 1) * 2;
for (int i = 0; i < thetaDiv; i++)
{
var w = (v * circle[i].X) + (u * circle[i].Y);
for (int j = 0; j + 1 < n; j++)
{
// Add segment
var q1 = origin + (direction * points[j].X) + (w * points[j].Y);
var q2 = origin + (direction * points[j + 1].X) + (w * points[j + 1].Y);
// todo:should not add segment if q1==q2 (corner point)
// const double eps = 1e-6;
// if (Point3D.Subtract(q1, q2).LengthSquared < eps)
// continue;
float tx = points[j + 1].X - points[j].X;
float ty = points[j + 1].Y - points[j].Y;
var normal = (-direction * ty) + (w * tx);
normal.Normalize();
this.positions.Add(q1);
this.positions.Add(q2);
if (this.normals != null)
{
this.normals.Add(normal);
this.normals.Add(normal);
}
if (this.textureCoordinates != null)
{
this.textureCoordinates.Add(new Point((float)i / (thetaDiv - 1), (float)j / (n - 1)));
this.textureCoordinates.Add(new Point((float)i / (thetaDiv - 1), (float)(j + 1) / (n - 1)));
}
int i0 = index0 + (i * rowNodes) + (j * 2);
int i1 = i0 + 1;
int i2 = index0 + ((((i + 1) * rowNodes) + (j * 2)) % totalNodes);
int i3 = i2 + 1;
this.triangleIndices.Add(i1);
this.triangleIndices.Add(i0);
this.triangleIndices.Add(i2);
this.triangleIndices.Add(i1);
this.triangleIndices.Add(i2);
this.triangleIndices.Add(i3);
}
}
}