#What IPAS do I Need?
16-Sep-95 16:47:27
Sb: #190705-#What IPAS do I Need?
Fm: John K. Jordan 71174,711
To: PETER CASANO 71172,2325
>>how can I reorient faces and edges…
Peter,
It is relatively easy to adjust a mesh an put edges and vertices exactly where
you want them. It requires some manual editing but is often necessary for a
smooth mesh. Of course, you need to properly apply smoothing groups to a mesh,
but as you have noticed, the mesh itself often needs adjusted. So, in case you
haven't done much low-level mesh editing…
The commands I use the most for this work are
Modify/Edge/Turn
Modify/Edge/Divide
Modify/Vertex/Move
Modify/Vertex/Weld
If an edge is oriented across a pair of faces such that it makes a sharp edge,
you can reorient it with MODIFY/EDGE/TURN. I use Turn a LOT to make efficient
meshes and to solve smoothing and rendering problems, especially after boolean
operations. The goal is usually to turn edges such that long narrow faces are
turned into less narrow faces. Use caution and the HOLD button however, since
it is easy in some circumstances to fold a face so it is hard to recover.
To add more faces to a critical part of the mesh, I often use
MODIFY/EDGE/DIVIDE to split a face into two. This gives me more control than
the tesselate command. Unfortunately, there is no EDGE/REFINE command similar
to the Shaper's SEGMENT/REFINE to place the new vertex exactly where you want
it. However, by aligning a user-view to the face, the new vertex can be moved
easily to the desired position. I often use EDGE/DIVIDE and EDGE/TURN together
to quickly adjust a mesh.
Most complex surface meshes need some vertex editing. After aligning a
user-view to a face, vertices can be moved without pulling the mesh
significantly out of shape. To move a vertex perpendicular to a user-view, use
the cursor keypad to quickly create a view oriented 90-deg to the current view.
When moving even a single vertex around in 3D, it is usually a lot easier to
select it first in one view and then move it "Selected" in a different view.
(Note: I do so much vertex editing, I rely on the assignable function keys with
Ctl-F7 as SELECT/VERTEX/QUAD and Ctl-F8 as MODIFY/VERTEX/MOVE. This saves me a
lot of time.)
To collapse a face, use MODIFY/VERTEX/WELD and drag a vertex and drop it on
another vertex. I generally do this in a user-view after first hiding all the
faces on the back side of the mesh.
One other thing I rely on when editing a complex surface is the real-time
wireframe mesh viewer built into the Yost Displace and Optimize routines.
Until someone comes up with a good stereo mesh viewer, I find it useful to use
one of these viewers to swing the surface back and forth, allowing me to get a
"feel" for the true shape of the 3D surface. This has proved to be invaluable
to help solve the occasional rogue vertex or face problem. Another thing I've
found helpful is to render the object with FLAT shading from different angles.
This renders very quickly and elimiates the rendered smoothing effects to help
me to see how the faces are oriented, which edges need to be turned or
subdivided, and which vertices need attention.
I realize this may sound like a lot of tedious work, but it will result in a
mesh exactly the way you want it. From your message, it sounds like you're not
afraid of a little edge editing. <g>
Note also that other techniques may apply depending on the mesh, like the 3rd
party SMOOTH IPAS mentioned by others here, more effective lofting techniques,
and the proper use of smoothing groups. Also, your specific problem of
correctly placed but unorganic-looking sinus blobs might be solved with a
boolean Union. I might try placing a sphere in the same position as the
existing sinus blob, manually flaring both meshes in the attachment area to
approximate a smooth junction, collapsing the original blob until it fits
entirely within the sphere, then unioning them together.
JKJ, Oak Ridge, TN