public static CrossSectionOfLine GetStarShapedPolygon(double innerRadius, double outerRadius, int starArms)
{
var result = new CrossSectionOfLine();
int numVertices = starArms * 2;
int numNormals = 2 * numVertices;
result._vertices = new PointD2D[numVertices];
result._isVertexSharp = new bool[numVertices];
result._normals = new VectorD2D[numNormals];
for (int i = 0; i < numVertices; ++i)
{
double phi = (Math.PI * (2 * i)) / numVertices;
double radius = 0 == (i % 2) ? outerRadius : innerRadius;
result._vertices[i] = new PointD2D(radius * Math.Cos(phi), radius * Math.Sin(phi));
result._isVertexSharp[i] = true;
}
// now the normals, we calculate them using the cross product with the z-axis
var zaxis = new VectorD3D(0, 0, 1);
for (int i = 0; i < numVertices; ++i)
{
var line = (VectorD2D)(result._vertices[(i + 1) % numVertices] - result._vertices[i]);
VectorD2D cross = new VectorD2D(line.Y, line.X).Normalized;
result._normals[(2 * i + 1) % numNormals] = cross;
result._normals[(2 * i + 2) % numNormals] = cross;
}
// normals
return(result);
}
public static CrossSectionOfLine GetSquareCrossSection(double width, double height)
{
var result = new CrossSectionOfLine();
double w2 = width / 2;
double h2 = height / 2;
result._vertices = new PointD2D[4];
result._isVertexSharp = new bool[4];
result._normals = new VectorD2D[8];
result._vertices[0] = new PointD2D(w2, -h2);
result._vertices[1] = new PointD2D(w2, h2);
result._vertices[2] = new PointD2D(-w2, h2);
result._vertices[3] = new PointD2D(-w2, -h2);
result._isVertexSharp[0] = true;
result._isVertexSharp[1] = true;
result._isVertexSharp[2] = true;
result._isVertexSharp[3] = true;
result._normals[0] = new VectorD2D(0, -1);
result._normals[1] = new VectorD2D(1, 0);
result._normals[2] = new VectorD2D(1, 0);
result._normals[3] = new VectorD2D(0, 1);
result._normals[4] = new VectorD2D(0, 1);
result._normals[5] = new VectorD2D(-1, 0);
result._normals[6] = new VectorD2D(-1, 0);
result._normals[7] = new VectorD2D(0, -1);
return(result);
}
public static CrossSectionOfLine GetRegularRoundedPolygon(double radius, int edges)
{
var result = new CrossSectionOfLine
{
_vertices = new PointD2D[edges],
_isVertexSharp = new bool[edges],
_normals = new VectorD2D[edges]
};
for (int i = 0; i < edges; ++i)
{
double phi = (2 * Math.PI * i) / edges;
result._vertices[i] = new PointD2D(radius * Math.Cos(phi), radius * Math.Sin(phi));
result._isVertexSharp[i] = false;
result._normals[i] = new VectorD2D(Math.Cos(phi), Math.Sin(phi));
}
// normals
return(result);
}
public static CrossSectionOfLine GetRegularSharpPolygon(double radius, int edges)
{
var result = new CrossSectionOfLine
{
_vertices = new PointD2D[edges],
_isVertexSharp = new bool[edges],
_normals = new VectorD2D[2 * edges]
};
for (int i = 0; i < edges; ++i)
{
double phi = (Math.PI * (2 * i)) / edges;
result._vertices[i] = new PointD2D(radius * Math.Cos(phi), radius * Math.Sin(phi));
result._isVertexSharp[i] = true;
double phim = (Math.PI * (2 * i - 1)) / edges;
result._normals[2 * i] = new VectorD2D(Math.Cos(phim), Math.Sin(phim));
double phip = (Math.PI * (2 * i + 1)) / edges;
result._normals[2 * i + 1] = new VectorD2D(Math.Cos(phip), Math.Sin(phip));
}
// normals
return(result);
}
