After having done a little of the WallGeometry, I figured it might make
sense to draw the LineStrip points with, well, a LINE_STRIP which
would of course be of a different color than the triangles drawing the
wall. now, for I already have the vertices for the whole thing, it would
make sense just to add another GeometryIndices object to the same
WallGeometry object, with a LINE_STRIP primitive.
but, as I understand, when combining the WallGeometry object with an
Appearance, thus creating a Primitive, there is no way to separate the
Appearance of the triangles from the appearance of the lines. thus, in
this case one cannot reuse the points (attribute positions) so that the
same points are used to draw the lines?