I have received an Iges-file exported from a 3D software. The wireframe model and surface seems ok, but the orientation of iges patches is quite random.
Is there a way to see and change the the direction of a surface? (surface normal pointing direction)
1 Like
I think you are looking for the Dir and Flip commands.
Select all and Join all the surface togetherm they will all go in the same direction then.
Join will only affect the BRep face normal, and will not affect the underlying Surface normal. If you see a small purple stick on the opposite side of the normal vector in the Dir command, the BRep face normal has been flipped, but not the underlying surface normal. In most cases this does not matter, but it is good to know about this subtle difference.
OK, thanks.
I think a new iges export of a joined surface will solve the case, but i ran into another problem when joining surfaces. I was not able to join all surfaces even if they were selected due to the open and closed polysurfaces. Can anyone tell me what’s the difference and how to join all into one surface?
Hi Jan - Iges into Rhino does not bring in joined surfaces. Joining in Rhino may unify the normals in a sense but not by changing the underlying surface UV directions, as menno mentioned above - what is the goal in having all the normals be the same?
-Pascal
A closed surface/polysurface in Rhino completely encloses a volume with no exposed, aka “naked” edges. An open surface/polysurface in Rhino has naked edges and does not completely enclose a volume.
Surfaces and polysurfaces can only be joined at naked edges in Rhino. Nothing can be joined to a closed surface/polysurface in Rhino.
A polysurface in Rhino is two or more individual surfaces joined together. In some instances separate surfaces can be merged together at untrimmed edges into a large single surface using MergeSrf.
Actually it can, just for the same of complete completeness, using NonManifoldMerge, but, yeah, that is not quite the same thing…
-Pascal
EASY FIX: Ask the lovely people who made the IGES export to re-send a .STEP file export.
If their app can make an IGES file, odds are excellent that it can make a STEP file. They just need to look around in the settings.
I run into this from time to time and have to educate the client or vendor. IGES has NURBS surfaces, but none of them stay joined. STEP has the exact same surfaces, but whatever was originally joined will stay joined. Nice!
3 Likes
Thanks, I got a step file instead, but I am experiencing same problems as with the iges. Zooming in shows gaps or surfaces with very small sides (approx. 1 mm). How to remove or close these surfaces or make a rougher surface mesh?
tolerances
mesh
meshtonurb
Those gaps are because the surfaces are not joined. You can join them manually and the mesh should adjust and the gaps will disappear.
Of course, if you have a polysurface with 10,000 pieces – all un-joined thanks to IGES – then its not worth fixing manually. Work with the STEP import.