//
// Steps Extrude
//
public static Surface Extrude(this Polyline curve, int steps, double height, double taper)
{
Vector3F normal = Vector3F.Undefined;
taper = (taper < 0 ? -1f : 1f) - taper;
if (curve.Points.Count < 2)
{
return(null);
}
if (steps < 2)
{
return(null);
}
steps = ((steps / 4) + ((steps % 4) != 0 ? 4 : 0)) * 4;
if (curve.Points.Count > 2)
{
normal = Vector3F.CrossProduct(new Vector3F(curve.Points[0].Point, curve.Points[1].Point), new Vector3F(curve.Points[0].Point, curve.Points[2].Point));
}
if (normal.IsUndefined)
{
normal = new Vector3F(0, 0, -1);
}
normal = normal.Unit();
Surface surface = new Surface();
for (double i = 0; i <= 1; i = i + 1 / (double)steps)
{
surface.Points.Add(curve.GetParametricPoint(i));
}
int num = 0;
Point3F sumBase = new Point3F(0, 0, 0);
Point3F sumHeight = new Point3F(0, 0, 0);
for (double j = 0; j <= 1; j = j + 1 / (double)steps)
{
Point3F item = surface.Points[num];
sumBase = sumBase.Add(item);
item.X = (item.X * taper) + (normal.X * height);
item.Y = (item.Y * taper) + (normal.Y * height);
item.Z = item.Z + (normal.Z * height);
sumHeight = sumHeight.Add(item);
surface.Points.Add(item);
num++;
}
sumBase.DivideBy(num);
sumHeight.DivideBy(num);
TriangleFace[] faces = new TriangleFace[(num + (curve.Closed ? 1 : 0)) * 2];
int k;
for (k = 0; k < num - 1; k++)
{
faces [k * 2] = new TriangleFace(k, k + 1, k + num + 1);
faces [k * 2 + 1] = new TriangleFace(k, k + num + 1, k + num);
}
if (curve.Closed)
{
faces [k * 2] = new TriangleFace(num - 1, 0, num);
faces [k * 2 + 1] = new TriangleFace(num - 1, num, 2 * num - 1);
}
surface.Faces = faces;
return(surface);
}