Hi Danny - shelling generally works best for thickening a surface when the surface is all completely smooth. When there are sharp corners in the shape the shelling mechanism in the geometry library that MoI uses does not deal well with that, it doesn't know how to extend the surfaces to meet at the juncture areas.
There is a second way to use Shell and that's by starting with a solid and then selecting the face that you want to use as an opening. That can help with the extension calculations because it gives a kind of "side wall" surface that the sheller intersects the extended surfaces with to form a flush matching area.
So often times if you want to shell something that's not all one smooth surface you would want to build it into a solid first, then select the face of the solid that you want to have as the opening and run Shell - try this with a box for example to see how that works.
But there can be additional issues with shelling too - the extended offsetting mechanism can get confused fairly easily. I don't think that it will properly handle the kind of juncture area you have here with 5 surfaces meeting up at one corner spot with some of them meeting up smoothly and some sharply. The geometry library's extended offset mechanism assumes that every original vertex will match to one single vertex in the generated offset and when you have shapes like you have here that's not the case. I've asked the authors of the library to improve this particular area, and they've been working on it for a while now.
Check out here for some previous discussions on things that are problematic with shell:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1209.2
http://moi3d.com/forum/index.php?webtag=MOI&msg=649.7
http://moi3d.com/forum/index.php?webtag=MOI&msg=133.11
http://moi3d.com/forum/index.php?webtag=MOI&msg=1939.10
If you did want to generate a shell from this you would probably need to do it in a more manual "low level" way of breaking the shape apart into individual surfaces and then doing an offset of each surface and then doing some trimming and surface modeling to connect the pieces.
- Michael |
