public static Mesh Revolve(this IVertexSource source,
int angleSteps = 30,
double angleStart = 0,
double angleEnd = MathHelper.Tau,
bool revolveAroundZ = true)
{
angleStart = MathHelper.Range0ToTau(angleStart);
angleEnd = MathHelper.Range0ToTau(angleEnd);
// make sure we close 360 shapes
angleStart = fixCloseAngles(angleStart);
angleEnd = fixCloseAngles(angleEnd);
if (angleStart == 0 && angleEnd == MathHelper.Tau)
{
angleSteps = Math.Max(angleSteps, 3);
}
else
{
angleSteps = Math.Max(angleSteps, 1);
}
// convert to clipper polygons and scale so we can ensure good shapes
Polygons polygons = source.CreatePolygons();
if (polygons.Select(poly => poly.Where(pos => pos.X < 0)).Any())
{
// ensure good winding and consistent shapes
polygons = polygons.GetCorrectedWinding();
var bounds = polygons.GetBounds();
bounds.Inflate(10);
// clip against x=0 left and right
var leftClip = new Polygon();
leftClip.Add(new IntPoint(0, bounds.Bottom));
leftClip.Add(new IntPoint(0, bounds.Top));
leftClip.Add(new IntPoint(bounds.Left, bounds.Top));
leftClip.Add(new IntPoint(bounds.Left, bounds.Bottom));
var rightStuff = polygons.Subtract(leftClip);
var rightClip = new Polygon();
rightClip.Add(new IntPoint(0, bounds.Top));
rightClip.Add(new IntPoint(0, bounds.Bottom));
rightClip.Add(new IntPoint(bounds.Right, bounds.Bottom));
rightClip.Add(new IntPoint(bounds.Right, bounds.Top));
var leftStuff = polygons.Subtract(rightClip);
// mirror left material across the origin
var leftAdd = leftStuff.Scale(-1, 1);
if (leftAdd.Count > 0)
{
if (rightStuff.Count > 0)
{
polygons = rightStuff.Union(leftAdd);
}
else
{
polygons = leftAdd;
}
}
else
{
// there is nothing on the left
polygons = rightStuff;
}
}
// convert the data back to PathStorage
VertexStorage cleanedPath = polygons.CreateVertexStorage();
var mesh = new Mesh();
var hasStartAndEndFaces = angleStart > 0.000001;
hasStartAndEndFaces |= angleEnd < MathHelper.Tau - 0.000001;
// check if we need to make closing faces
if (hasStartAndEndFaces)
{
// make a face for the start
Mesh extrudedVertexSource = cleanedPath.TriangulateFaces();
if (revolveAroundZ)
{
extrudedVertexSource.Transform(Matrix4X4.CreateRotationX(MathHelper.Tau / 4));
extrudedVertexSource.Transform(Matrix4X4.CreateRotationZ(angleStart));
}
else
{
extrudedVertexSource.Transform(Matrix4X4.CreateRotationY(angleStart));
}
mesh.CopyFaces(extrudedVertexSource);
}
// make the outside shell
double angleDelta = (angleEnd - angleStart) / angleSteps;
double currentAngle = angleStart;
if (!hasStartAndEndFaces)
{
angleSteps--;
}
for (int i = 0; i < angleSteps; i++)
{
AddRevolveStrip(cleanedPath, mesh, currentAngle, currentAngle + angleDelta, revolveAroundZ);
currentAngle += angleDelta;
}
if (!hasStartAndEndFaces)
{
if (((angleEnd - angleStart) < .0000001 ||
(angleEnd - MathHelper.Tau - angleStart) < .0000001) &&
(angleEnd - currentAngle) > .0000001)
{
// make sure we close the shape exactly
AddRevolveStrip(cleanedPath, mesh, currentAngle, angleStart, revolveAroundZ);
}
}
else // add the end face
{
// make a face for the end
Mesh extrudedVertexSource = cleanedPath.TriangulateFaces();
if (revolveAroundZ)
{
extrudedVertexSource.Transform(Matrix4X4.CreateRotationX(MathHelper.Tau / 4));
extrudedVertexSource.Transform(Matrix4X4.CreateRotationZ(currentAngle));
}
else
{
extrudedVertexSource.Transform(Matrix4X4.CreateRotationY(angleStart));
}
extrudedVertexSource.ReverseFaces();
mesh.CopyFaces(extrudedVertexSource);
}
mesh.CleanAndMerge();
// return the completed mesh
return(mesh);
}