Q:

What is mesh geometry?

What is mesh geometry in WPF?
<MeshGeometry3D Positions="0,0,0 10,0,0 10,10,0 0,10,0 0,0,10 10,0,10 10,10,10 0,10,10"
                TriangleIndices="0 1 3 1 2 3  0 4 3 4 7 3  4 6 7 4 5 6  0 4 1 1 4 5  1 2 6 6 5 1  2 3 7 7 6 2" />

This is the code I have, and what is the meaning of the numbers in Positions and TriangleIndices?

A:

MeshGeometry3D allows the developer to
  specify position, normal, and texture
  coordinate information. The Positions
  property is required.
Normals are assumed to be associated
  with the front faces of a mesh
  primitive. The winding order (the
  order in which the Positions that make
  up each triangle of the mesh are
  specified) determines whether a given
  face is front-facing or back-facing.
  Front-facing triangles are wound in
  counter-clockwise order; back-facing
  triangles are wound in clockwise
  order.

MSDN
Positions:

The points specifed by this property
  represent the vertices of the
  triangles that make up a 3-D mesh.
The winding order (the order in which
  the Positions that make up each
  triangle of the mesh are specified)
  determines whether a given face is
  front-facing or back-facing.
  Front-facing triangles are wound in
  counter-clockwise order; back-facing
  triangles are wound in clockwise
  order.

TriangleIndices:

For a triangle in a given 3-D mesh,
  the order in which the triangle's
  vertex positions are specified
  determines whether the triangle face
  is a front or back face.
The Windows Presentation Foundation
  3-D implementation uses a
  counter-clockwise winding order; that
  is, the points that determine a
  front-facing mesh triangle's positions
  should be specified in
  counterclockwise order, as viewed from
  the front of the mesh.
Setting the TriangleIndices property
  is optional. If the indices are not
  specified, triangles are drawn in a
  non-indexed fashion. Every set of
  three positions becomes a triangle.

