Cutting a mesh

[Tom Krowka]

Ok, here's another one I haven't run into before, and can't seem to figure out. I have an irregular shape inside a terrain mesh that I want to keep, but I want to delete the rest of the terrain mesh. This will enable me to retain the fairly complicated contours of the part I want to keep, change materials, then do an SEO on the original mesh.

I know I could just create a new mesh, but am creating the original mesh by picking points and would be much easier to simply use the piece I have than create another one. I just can't figure out how to get it out of the middle of the large mesh, which is a 4 acre site.

Thanks.

[Karl Ottenstein]

Several ways, Tom.

Duplicate your mesh.

On the copy, you can use the Split command if the part you want to cut out has straight edges. Repeat until you've cut away everything except the bit that you want.

Or you can use the pet palette's polygon substraction operation to create any shape to cut away... it will take at least two subtractions to leave the bit you want that's in the middle of your existing mesh. (A better description would be polygon erasure, I suppose, to avoid confusion with a Solid Element subtract. The icon has a polygon and a "-" next to it.)

On the original mesh, assuming you want the kept part deleted so that the two don't overlap, you can again use the polygon subtract (or the normal polygon hole technique) and magic wand the border of the kept bit to cut a hole.

Or you can do an SEO on the original mesh as you mentioned vs cutting a hole...

[Tom Krowka]

Yeah I guess I could do the multiple polygon subtraction method. Time consuming however. I have a big site with several parking areas that are delineated by polyline. I select the terrain, then the parking polyline that surrounds the parking area with the magic wand after selecting the "-" icon on the pet palette.

Every time it cuts the parking lot out and leaves a really nice hole. I tried using p.line segments that run past the borders and cutting away outside edges all around the parking lot. Crashed several times...or I would get a memory full error message and a frozen computer. Also tried cutting the mesh on the lines with the cut tool, but it had no effect.

Maybe I'll put on the wish list.....a command on the subtract icon so you can specify which piece to delete, the inside or the outside of the polygon.

Thanks....Tom