failed subtractions

[Artifex]

I am currently working on a model of a building with vaulted roofs (vw 8.5.2)and am experiencing some odd behavior with the extrusions I have created. The extrusions are basically tubular forms which I have then trimmed by subtacting other solids from them in order to create barrel vaults and cross-vaults. Upon completion they apear fine and render properly, but if I close the file and then come back to work on it they invariably have dissapeared only to be replaced by objects only visible in wireframe and identified as "failed subtractions". Any suggestions or work-arounds?

[rjk]

I have had considerable difficulty with what the program classifies as "failed additions".

I created scaffolding units consisting of tubular piping ( extrudes ) which were then joined with both unedited and subtracted pieces which were then completed by the addition command.

After saving and reopening -some - but not all -of the units have "exploded" into boxes.

If I then select each box and "ungroup" most will revert to their pre addition state.

If I figure out why--I'll post.

[Davide]

I don't know if 9.5 fixed the problem which I encountered too in 9.1. Solution: convert your shapes ( while you still have them) in 3d polygons or ,even better, meshes. Every object that is "smart" ( they have a history to go back through like symbols, groups, extrusion solid boolean operations plug ins etc) can fail, a bunch of 3d polygons can't go anywhere. Obviously you'll lose the editing flexibility.

[rjk]

But why do they fail? Anyone have background on this? Or is there a tech note that deals with it that I have not been able to find?