3D circle projected on 2D

Question

If you have a 2D circle sitting inside 3D space and you point to it with a virtual camera, what will the projection look like? Will it always be an ellipse? Is there an easy way to calculate this ellipse?

How can I write this in java for example.

class Point3D { int x,y,z; } class RotatedEllipse extends Ellipse2D.Double { double rotation; } public static RotatedEllipse circleProjection(Point3D center, int radius, Point3D normalVector, Camera camera) { ... return new RotatedEllipse(...); }