Mesh . . not able to elevate contour or node with out error

[Anonymous]

I have a mesh I have been working with for a while no with no problems, and now everytime i try to do any little thing to it I get invalid polygon messages.

"Invalid Polygon, Self intersection or hole intersects boundary."

Even if I don't change anything it does it, like I just went to a contour and said go to Z value, and didnt change it, just said OK, and it still gave me the rror message.

[Anonymous]

Hello Jess,
One of the most common uses of independent points
is when say you want a swale that is between two adjacent contours.
You do not want a ridge line that is between your standard contour intervals.
Any time you want to manipulate the grade between standard contours
intervals you use independent points.
Surface fitting is where AC creates a mesh contour line whose nodes
lie on the surface of the mesh as it is at each new node point. The
consequence of this is the elevation of each node is different even though
they lie on the same contour line. The whole system of contour lines is that
all points that are at the same elevation form a contour line. So you do
not want to violate this system by having a contour line that has nodes
that are not all at the same elevation. I recommend, and some disagree,
is when creating a new contour using the magic wand do not enable
surface fitting which creates the new contour with all nodes at zero
elevation but they are all the same. Later you assign all of those nodes
the elevation you want.
One important use of surface fitting is when you want to show with a line
where the terrain intersects some element like an exterior slab and don't
want to cut a hole in the mesh to get this intersection line. You draw a
line around the perimeter of the slab select the mesh, turn on the mesh
tool, and magic wand this line but when prompted you select the
surface fitting option. Since these kinds of lines are not official contour lines
but object lines they can have nodes of differing elevation.
I hope this makes sense.
Peter Devlin

[Anonymous]

Hello Jess,
I would like to refer you to two links that have discussions about meshes.
The first is to James Murray's site and his discussion of terrain meshes.
http://www.onland.info/archives/2008/08/mesh.php

The second is a discussion by Lazlo Nagy on ArchicadWiki
http://www.archicadwiki.com/Mesh

James' discussion is quite extensive and is excellent .

Lazlo's discussion is more specific but also excellent.

Peter Devlin