Shelling complex surfaces

[dklarz]

I'm battling what I think should be a fairly simple problem but am drawing a blank. I have an imported solid of a model that has some fairly complex surfaces. I'd say a doll head is a pretty good example of what I'm dealing with. What I need to do is shell it out. I've tried shelling the solid but get a minimum radius of curvature error. So I thought I'd surface it and thicken the surface but that didn't work either. Am I going about this the right way? Any suggections? Thanks - DadeLar

 

[CorBlimeyLimey]

The "minimum radius of curvature" error refers to a situation where the thickness of the shell would create a negative inside radius. eg. Outside radius of 1mm, thickness is 1.5mm, so inside rad needs to be -.5mm ... which of course is impossible ... hence the error.

You will have to live with a thinner wall thickness or increase the outer radius.


SW07-SP3.1
SW06-SP5.1

 

[CorBlimeyLimey]

... or create a set of inside surfaces which eliminates or avoid the inner rad problem.


SW07-SP3.1
SW06-SP5.1

 

[Theophilus]

I've done this by doing partial offset surface features. Select chunks of the outer surface to offset inward at your desired shell depth. You'll find the problem surface along the way--but it's often an intersection of the surface that does this--so you may also find the border that causes the problem. By breaking the offset into chunks, you eliminate the border-caused problem (if you select the chunks properly).

So it can take some trial-and-error, but will almost always work if done this way.

After all surfaces are represented in the offset chunks, you can trim/knit them to create the inner surface. Use that surface to perform a surface cut to eliminate the internal solid mass, and you're left with your shell.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[overkill04]

I've also had success in this realm by doing an extruded cut, with the offset from surface option selected. As long as your "dolls head" consists of one continuous surface.

It seemed to have more luck dealing with the resulting geometry than the shell command which I've found to be less than robust.





Specs, Intel Pentium M 2.16 Mhz
SW 2007 R2.2
1.5 Gb Ram
NVidia GE Force GO 6800 256Mb

 

[rfus]

Have you used tools -> check... -> min rad of curvature on the surface. This may help you in your thickening attempts.

For a manual method, you may want to select all faces on the outer surface of this 'doll head'. Select offset surface and enter a value of 0. This will copy the surface, and this shoulb be considered a singualr knitted surface if it was a solid. Then offset the surface twice, once inward and once outward. What is the max you can offset it inward without collapsing it about a min rad of curvatue ? What is the max you can offset it outward while maintianing the form? You could then insert a plane down at the 'neck' and trim these inward and outward surfaces to it. Create a planar surface between these inward and outward surfaces. You now should be able to knit all three together with try to form solid checked. If this is not possible, then you are going to have to use more complex techniques like the ones mentioned by jeff and CBL.

RFUS

 

[Theophilus]

Try rfus' solution first--it's simpler if you can get it to work for you. Back before surfacing had many tools (SW 99?), I used overkill04's method to get what I needed with a series of offset-from-surface cuts. However, that technique can also be quite fragile if you make upstream edits that change your geometry--since within a doll-head sort of shape you'll need to make a series of such cuts to get the job done.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[Rocko]

Dadelar,
If you shell out of course the radii will be larger versus the interior model you started with, is this a problem?
Can you use offset surfaces command ?