  In this work, we propose an automatic mesh generation algorithm, FlowMesher,
which can be used to generate unstructured meshes for mesh domains in any shape
with minimum (or even no) user intervention. The approach can generate
high-quality simplex meshes directly from scanned images in OBJ format in 2D
and 3D or just from a line drawing in 2-D. Mesh grading can be easily
controlled also. The FlowMesher is robust and easy to be implemented and is
useful for a variety of applications including surgical simulators.
  The core idea of the FlowMesher is that a mesh domain is considered as an
"airtight container" into which fluid particles are "injected" at one or
multiple selected interior points. The particles repel each other and occupy
the whole domain somewhat like blowing up a balloon. When the container is full
of fluid particles and the flow is stopped, a Delaunay triangulation algorithm
is employed to link the fluid particles together to generate an unstructured
mesh (which is then optimized using a combination of automated mesh smoothing
and element removal in 3D). The performance of the FlowMesher is demonstrated
by generating meshes for several 2D and 3D mesh domains including a scanned
image of a bone.
