What does offset mean, laterally?
Export surface via LandXML. Rename current surface. Import LandXML.
I am sure you can just move it laterally, I have had no reason to try it.
I'm a little confused by your explanation, but I think that what you are trying to do is create a copy of the existing surface that is lowered by a certain amount.
If so, create a new surface and use edit-"paste surface" to paste the existing surface into that one. Then use edit-"raise/lower surface" to lower that surface by the amount.
You will then have two surfaces.. the existing.. and the "excavation" surface.
Hi, wfberry! Maybe I wasn't clear enough - i have to offset existing surface normal to itself, not move it laterally - but can't realize the way to do it in C3D... I can extract triangles from existing surface and than offset them using surfoffset command and create TIN again, but this method is not very accurate and it is time consuming. I'm looking more automatic and more ACCURATE way to do it... Let say that offset surface represent excavation line and has to be very accurate in this case.
No kidding. What happens when two normal vectors intersect at the offset distance? Or diverge and the surface area gets larger? sounds undefined and redefined to me.
What are you building that a datum excavation wouldn't give a close enough representation of the volume?
No kidding. What happens when two normal vectors intersect at the offset distance?
Please, see picture I have posted in my earlier post.
I said that offset line represent excavation line not that i'am looking for excavation volume. What i'am looking for are new positions of grade brake points
on the offseted surface.