From: Art (ARTURBRZUZA)
Hi, I am not getting the proper result from running a network and then shell. The tip looks bad. I assume this might come down to the curve itself being made incorrectly? I used freeform>throughpoints to get some of the base curves to build the network from. Any suggestions?
Attachments:
ElbowGuard.3dm
Image Attachments:
shellproblem.jpg
From: ed (EDDYF)
Art -
I was able to get a nice Shell result by restructuring the Network:
1. Select the two black curves and Join into a single curve.
2. In top view, split the blue and green curves in half where they cross each other. I used Trim points for that. Make sure the curves touch at a single point. Make sure the curves touch the joined black curve.
3. Optionally you can place a small circle where the 4 curves meet at the top. This can help smooth the Network where the points converge.
4. Select all curves and Network. Shell the result.
Sometimes you get pinching with a Network and the Shell amplified that pinching. When that happens I try other Network structures.
Ed Ferguson
From: Michael Gibson
Hi Art, yes the pinched shape that Ed is talking about is a little difficult to see, here is a zoom in on it:
That thing that looks like a little dimple there is a spot on the surface where the surface normal is shooting around kind of chaotically in a very small area. Such things are bad for generating surface offsets. Making an offset is kind of like taking a stick and running it along the surface and making a new surface at the tip of the stick. It kind of magnifies surface anomalies like this.
One way you can get better surface quality is to build an extended surface initially that has 4 distinct corners and then trim away an outside outline, rather than making a surface with "poles" in it like you have here.
- Michael
Image Attachments:
art_dimple1.jpg
art_dimple2.jpg
From: Phiro
Perhaps, is it possible to fix the pinching problem ?
1/ First test
You cut a band zone where your pinch appears in the center of the surface then you blend the two pieces.
The shell made next is not a solid
2/ Second test
You cut the bottom of the piece with its own (flatted and moved up) profile.
The shell made next is a solid
Not perfect but you can test...
From: Phiro
Image Attachments:
elbow_test_moi.PNG
From: Michael Gibson
Another thing that can help with shaping at the poles of a Network is to add a circle or arc section right before the pole point. That can help sort of even out the shape as it approaches the pole.
Something similar to the attached.
- Michael
Attachments:
ElbowGuard2.3dm
From: ed (EDDYF)
The thing I really like about MoI is that there is usually one or more methods available to accomplish a result.
In addition to the Network restructure I showed in the earlier post, you may want to try Rail Revolve.
I got a nice surface by joining your two black curves (the rail), and using one-half of the blue curve (the profile) in a Rail Revolve, followed by a Shell.
Taking it a step further, I made two profile curves with a rounded bottom and an indented feature near the top to show what's possible. These profiles will also give a thicker result near the top, something Shell can't do.
Rail Revolve the orange profile curve around the black rail, then repeat using just the red profile curve. Select both surfaces and Join into a Solid.
The nice thing about Rail Revolve is you can easily modify the profile curves, and also avoid using Fillets if you construct the profiles with a small radius.
Ed Ferguson
From: Art (ARTURBRZUZA)
Yes Michael this works better, however there still appears to be an issue when attempting to shell. Ed got it to shell cleanly so I will follow the suggestions given in a bit. The loops I've seen on other peoples networks makes sense now though.
From: Art (ARTURBRZUZA)
Thankyou everyone for your input. Following ED's little tutorial and tips from others I was able to get the right results. One funny thing though, my view port after performing the shell command displays a polygonal silhouette, though if I export and set angle setting low the geometry is smooth. In the past I would simply lower meshing angle in view options but here it doesn't seem to react at all. (Edit: No wait, its only appearing polygonal when shell is set to flip...bug? Viewport? )
In any case, its not really an issue for me.
Image Attachments:
shellissue.jpg
From: Michael Gibson
Hi Art, I'm glad you've got a good result!
The "polygonal look" in the silhouette is a normal display artifact. Surfaces are actually drawn by internally converting them to triangles and then displaying the triangles. There aren't quite enough polygons being generated in that particular area for it to make a smoother looking display.
Various parts of the display engine are more tuned to having a fast display instead of having perfect quality so some kinds of display artifacts including this one are just normal and should just be ignored.
In the future at some point I would like to generate a denser mesh on a background thread that's adapted to the current view which would help with this. That will be fairly complex to set up so I'm not sure when that will happen.
- Michael
From: Art (ARTURBRZUZA)
Right on, thank you for the detailed reply. I figured it was something related to the code.
Image Attachments:
uyu.jpg
