Rhino has about a thousand unnecessary clicks and steps that really tears on my RSI, but one that doesn’t just do that, but also either fails or creates infuriating mistakes you don’t immediately notice, is the implicit trim direction that Rhino creates internally without ever showing or telling you.
Yes, people have explained the hidden rules that govern this to me many times. It doesn’t matter, because I shouldn’t have to spin the model around in order to see if an edge or curve might be planar in some angle.
99% of the time, I want to Trim Direction=Normal (or Pull as Rhino calls it).
I’ve only used Rhino for a year, but I think I’ve already wasted several hours on figuring out why my Trims so often fail, and these days, I often go through the extra steps of DupEdge/Intersect, Fin and 3xExtendSrf which is a chore.
(Now, an ExtendCuttingSurface option in addition to the current line option (which never works) would also be nice, but I’ll keep this topic to the above single request.)
I’m surprised you have to ask that question. You don’t have a preference that you’d use 99% of the time?
I come from a different software package where you were allowed to select the direction, and in that tool I set it to target surface normal back in 2009, and I still haven’t changed it!
I just trim with surfaces, because I am lazy to keep track which view I am currently at or what Cplane I was using last. So I just extend the curve as surface and see if it is going where I expected, then I trim surface with surface.
Ok. Just to be clear. I’m posting in the V7 forum, not the V6 forum. So both of you are happy to waste seconds, turning into minutes, turning into hours, and neither of you want this feature to be added to Rhino?
Are you happy with the status quo, or are you just resolved that this is another of the 10k+ issues that they’re tracking that will never get resolved?
Yes, I am, but I probably don’t do the same kind of stuff you do or have the same expectations.
The question is, given a TrimDirection=TargetSurfaceNormal option might be available, how do you propose that it should work reliably? Trim can trim curves, surfaces and polysurfaces in one operation and not only by mouse picking, but also by window, crossing, lasso and brush selection of objects. I can see how it might be made to work reliably using a single curve to trim a single surface, but what about a polysurface that does not have tangent or curvature continuous joints? Which surface normal should it use?
Also it seems to me that if the trim curve is pulled to the surface along the surface normal, depending on the distance of the curve from the surface, the trim could be different - or could miss the surface entirely…
Maybe post an example of how you expect this to work?
No because your workflow sounds weird if this is causing you so much apparent grief. So if you’re in an orthographic view trimming off an object with a flat curve, you STILL want it to Pull? How do you ever precisely trim anything?
It’s not a mystery. I’m reluctant to mention other threads and other software, but so many problems that exist in Rhino are solved problems in other software packages (yes, yes, why don’t you use them instead I hear you say… I’m hoping that I could use Rhino all the time, and I’m hoping V7, V8 etc will improve instead of standing still).
I almost never use orthographic views. I’m not an engineer, I’m a designer, and what I design is very three dimensional. Trimming in ortho views work mostly with flat surfaces, and mine tend to curve a lot.
I don’t know… how do CAD other packages ever trim anything precisely?
I don’t understand why the Rhino community finds this concept so alien, when the rest of the CAD world has used it as standard for the last two decades…
Rhino’s inconsistency, when it comes to trimming surfaces/polysurfaces with a curve, forced me to always use either a straight extrusion (! _ExtrudeCrv _Pause _Solid=_Yes _Multipause _SelNone _SelLast) or an extruded curve on surface (! _Fin).
If I’m working in a 3D view, what’s the most likely scenario here? That I want to trim according to what I have right in front of me, or that I want to trim according to some other view which I don’t have active?
I mean sure, keep CPlaneZ in orthogonal views, but when working in the Perspective view, the default for all commands needs to be Normal/Pull to avoid errors which you don’t immediately detect!
Your “industry standard” of “normal to face” is ONLY and answer when the target is planar. If the target is not planar there is not a single direction normal to the target. That is basic geometry. What would be the “normal direction” for this example? Nonplanar Example.3dm (1.9 MB)
Seems I have been living in a very spoiled corner of the industry, because I tried to look up how to do this in Creo and Inventor and couldn’t find it. Then I asked a coworker who uses Catia, and sure it’s possible, but you have to embed a projection into the Split tool.
I never had an issue in NX/Alias with trimming non-planar surfaces, but if you need a single normal value a good start would be at UV length 0.5 which I still think would be better than CplaneZ in 90% of the cases in a 3D view. And in the topic I also wrote pull which would hopefully yield a 99% correct trim/split output in the case of non-planar surfaces.
But I guess it’s time to look into building a small script/macro which does all this for me.
