/// <summary>
/// Calculate the moment of inertia for a solid polygon shape assuming its center of gravity
/// is at its centroid. The offset is added to each vertex.
/// </summary>
public static double MomentForPolygon(double mass, IReadOnlyList <Vect> vertices, Vect offset, double radius)
{
IntPtr verticesPtr = NativeInterop.StructureArrayToPtr(vertices);
double moment = NativeMethods.cpMomentForPoly(mass, vertices.Count, verticesPtr, offset, radius);
NativeInterop.FreeStructure(verticesPtr);
return(moment);
}
/// <summary>
/// Calculate the natural centroid of a polygon.
/// </summary>
public static Vect CentroidForPoly(IReadOnlyList <Vect> vertices)
{
IntPtr verticesPtr = NativeInterop.StructureArrayToPtr(vertices);
Vect centroid = NativeMethods.cpCentroidForPoly(vertices.Count, verticesPtr);
NativeInterop.FreeStructure(verticesPtr);
return(centroid);
}
/// <summary>
/// Calculate the signed area of this polygon. Vertices specified such that they connect in
/// a clockwise fashion (called winding) give a positive area measurement. This is probably
/// backwards to what you might expect.
/// </summary>
public static double AreaForPoly(IReadOnlyList <Vect> vertices, double radius)
{
IntPtr verticesPtr = NativeInterop.StructureArrayToPtr(vertices);
double area = NativeMethods.cpAreaForPoly(vertices.Count, verticesPtr, radius);
NativeInterop.FreeStructure(verticesPtr);
return(area);
}
private static IntPtr CreatePolygonShape(Body body, Vect[] verts, double radius)
{
Debug.Assert(verts.Length > 2);
IntPtr ptrVectors = NativeInterop.StructureArrayToPtr(verts);
IntPtr handle = NativeMethods.cpPolyShapeNewRaw(body.Handle, verts.Length, ptrVectors, radius);
NativeInterop.FreeStructure(ptrVectors);
return(handle);
}
private static IntPtr CreatePolygonShape(Body body, IReadOnlyList <Vect> verts, Transform transform, double radius)
{
Debug.Assert(verts.Count > 2);
IntPtr ptrVectors = NativeInterop.StructureArrayToPtr(verts);
IntPtr handle = NativeMethods.cpPolyShapeNew(body.Handle, verts.Count, ptrVectors, transform, radius);
NativeInterop.FreeStructure(ptrVectors);
return(handle);
}