iges import

[rasesh]

Hi All Pro/E Gurus,


When i am importing an iges file in ProEngineer ,on import Pro gives me geom check errors such as "Original import surfaces have been split into highlighted pieces
due to G2 discontinuities".Does anybody know what this means?


Thanks in advance

 

[walkerone]

Surfaces have quality - and depending on how the IGES file was created, it can be a surface "structure" (see Wilikipedia http://en.wikipedia.org/wiki/IGES).


An extract from a surface quality website (can't credit it as I've lost the link...)


The quality of a connection can be measured at several levels of continuity, conventionally designated as G0 through G3. Briefly, a connection which is G0 has positional continuity resulting from a common extremity or border, i.e., the elements are connected. A G1 continuity exists when tangents at the junction point are co-linear. A lack of G1 continuity produces an edge in the combined curve or surface. Two curves or surfaces are G2 continuous at their junction when there is a G1 continuity and the amplitudes of curvature are equal at the junction point. Finally, a G3 continuity exists at a curve or surface junction when the tangents of the curvature envelopes are co-linear at the junction point. If joined curves or surfaces are not G2 and G3 continuous, reflections from the modeled object can contain visual artifacts, such as unexpected bends or kinks, which could detract from the overall appearance.


So, basically Pro/E is having difficulty at an interesction of two surface beacause the surfaces are causing discontinuities where they join - and Pro/E has attempted to fix it.


The question is, what are you using the IGES import for? Does it matter that the surface representation has been changed?

 

[jeff4136]

Actually, Pro/E is splitting the surfaces on import because it's detecting
a curvature discontinuity in the surface.


I believe I've also seen the same warning message come up when cylindrical
surfaces are read in as single closed surfaces rather than two 180 degree
segments (Pro/E splits them on import). If there's a Geometry Check; try
Edit Definition (the import feature) and look to see if there's a Geom Chk
listed there as well. If not, just OK out and I ~believe~ it will be
cleared in Standard Mode as well. It's been a while and I don't have a
sample to test offhand. It ~may~ be necessary to cycle Joining off and
back on (Edit / Feature Properties, or something like that) to sort it out.


If I'm not misremembering and understand what's going on the message is
off the mark because that case has nothing to do with G2 continuity, but
Pro/E's dislike of single closed surfaces.


The 'real deal' I've seen on surfaces created in Rhino, maybe other
programs as well but can't remember a specific instance. I've meant to
present it to the folks on Rhino's forum and see what comes of it but
never go a round tuit. I ~think~ it is often related to internal knot
multiplicities [#1] greater than one, which Rhino sometimes creates with
Sweep and Blend functions (and, I guess, some other programs may, as well)
. I've also seen cases where I believe tolerance values (on either the
creation / export or import end) will cause surfaces to be split.


[#1]: While b-spline curves and surfaces are generally curvature continuous
NURBS does allow knots to have multiplicity values greater than one. This
means that a single curve or surface ~can~ have curvature or even tangent
discontinuities, e.g. G0 where knots are 'fully' (entity degree) multiple.


- - - - - -
There is a related config option: try_g2_fix_on_import
that may help in some cases.
- - - - - -
Edited by: jeff4136

 

[arroyopr]

Try using the feature Heal Geometry. Frist try using the automatic option, that might a few surfaces then try manually to complete healingall surfaces.

 

[jeff4136]

FWIW, I advise caution where Auto healing is used. I rarely use it except for quick-n-dirty, sometimes without anxiety for relatively simple geometry (for which it's fine) and usually with an unhealed copy on hand for use as a 'standard' reference.


(Seems I've seen a discussion somewhere indicating WF4 removed themanual healing functions from Data Doctor? Bad move, IMO, if that's the case.)