Trimming a polysurface, from a curve?

Hi Im trying to trim the edges of a poly surface so it matches up nicely to the edge of this revolved shape ive made.
ive tried splitting, trimming every which way i can think of. I am not sure how to achieve this.
im open to better ways of doing this etc.

any help would be great, thank you

It is difficult or impossible to diagnose a problem without a file with the geometry. You can upload a .3dm file using the vertical arrow above where you type your post.

Use Intersect or IntersectTwoSets on the surface/polysurface to be split or trimmed and the splitting or trimming surfaces/polysurfaces and look at the results. The intersection curve needs to be either a closed or run continuously between edges of the surface/polysurface to be split or trimmed. Also the intersection curve cannot be folded back on itself or overlap itself. Use Show Ends or CrvStart and CrvEnd to see the ends of the intersection curve. If the intersection curve is not either a closed curve or continuous between edges then a surface needs to be modified. Sometimes it can help to extend the surfaces/polysurfaces past each other rather than have one end at the other.

BDP TESTING.3dm (203.1 KB)

thank you heres the file, i will try what youve outlined in the mean time.

your problem is that the curve does not sit right on the surface, when you use the command intersect then you see that the curve touches the surface only at certain spots,

how did you produce that curve?

you can offset it with option both, then loft the resulting curves to create a surface which you use to trim off the upper part, but that is not a good move because the imprecisions you have piled up will lead to further problems again, meaning you will not be able to join it to the other parts which i assume would be your next step.

i would rebuild that once more and try to make all the surfaces as precise as possible.
maybe start with that profile curve, having kinks always produces unneeded polysurfaces, that will help you having more control over the further modeling process.

So I drew the curve and snapped it to the profile of the rim I produced, I then added the extra poly line as I wanted the over hang to trim back all the way around. then i revolved it around.

when you say as precise as possible. how can i be more precice tham snapping to that profile line?

What command do I use to trim the surface, is it trim? Or split? Or…?

i have no idea which polyline you are talking about, i can see none… i assume you are talking about adding a curve after that kink i indicated? its best not to add an extra curve like that, if you are intending to create one revolved surface and seeking for quality. you can try ContinueCurve or ContinueInterpCrv if you want to extend the curve drawing if further. you can also try Extend but best would be if you make up your mind about such shapes before you draw. you can also use the command match set to curvature and merge if you have drawn an extra curve and want to create a continuous curve, sometimes restarting from scratch is the best way to achieve good quality. anyway the profile curve is just secondary for this problem. actually i meant how the curvy curve around the perimeter was produced since it obviously does not intersect the rest properly.

yes i was talking about the curve after the kink.
when it comes to redrawing the curved line how can i ensure i can revolve it around and get the right kind of intersection? to get the trim to work. it just doesnt like the curve ive drawn.

perhapse there is a better way to achieve what im trying to do?

Hello - Explode the polysurface - the curve will trim the top surface just fine by itself, then join the pieces back.


BINGO! thank you. :slight_smile:

that is indeed faster, but also faster leading into further problems :smiley: it will still not be possible to join the perimeter surface to it… but whatever. feeling like running after clouds.

MatchSrf > ChainEdges, for Position. Refine set.


that is going to change the surface. really… i would suggest rebuilding that completely. just for the fun and for the precision and experience.

Exactly. That is the goal. It does not join as is.
Another approach, @cdeluca is to ExtendSrf the wavy surface through the outer surface and trim them to each other.


it will change the surface in a more or less uncontrolled manner, that should not be the goal at least imho.

would you be able to suggest a better way to rebuild it, so it more accuratly so it joins?

no, because you still did not answer how you produced the wavy curve that i can suggest a better approach. it is not a complicated model, just rebuilding it from scratch with better curves may already solve it all. it seems when you explode as pascal suggests that it indeed coincides with the surface so you mus´ve done something right there. you are not far away from a better (joinable) quality.

Oh when you said curve i assuumed you meant the profile curve that was causing the issue.

That wavy curve was adapted from another file I have, for some reason my work computer doesnt seem to be able to uniformaly move the points of a circle up and down. i wanted a smooth uniform wave and for some reason drawing a default circle curve and manipulating the points didnt work. so i just took that curve from the file and removed the points.

ic. that most likely is responsible for your issues here now. but deforming a circle as you did should not cause any problems. only if the points (cp´s) are not lying on the same axis and you used something like scale1d would it increas distances i imagine now. you can use setpt to asure they are on the same level. but when creating that from scratch that should not cause issues. you can also use pull once you are done with that wavy curve to pull it to the surface, or you use InterpCrvOnSrf to draw that wavy curve directly on the surface best would be to place a few marker points that you can draw easier. but for this you for sure need one continuous surface so start with rebuilding that profile. after all that trim, loft or do what you did. there are a few approaches, best you try them all to see the advantages for later.