Patching a Hole
Patching a Hole
(OP)
Hello all.
I have this helmet bubble that I built from a VSS. But due to its odd shape, there was no way to terminate the bubble cleanly at the top. So an irregular hole is at the very top. I sliced the top just slightly larger than the hole with a cut so that at least the irregular hole was 2-dimensional. I can fill that hole boundary to make it a flat surface, but so far have not found a way to create a smooth patch to satisfactorily follow the bubble tangencies all the way to the apex of the bubble. In other words, I thought maybe I could apply a freeform blend to the flat surface, but the problem there is that the freeform surface that results does not terminate on the irregular hole boundary; it becomes a warped mesh rectangle instead that floats over the hole.
I also tried Edit>Extend, but that only allowed me to extend the bubble surface about .2 inch. My hole is a good 1 inch across.
Is there any procedure that works to fill up irregular (or even symmetrical) holes in geometry in ProE? A mesh would be fine I suppose, but at least a mesh whose boundary points land on the hole boundary.
Thank you very much,
treddie
I have this helmet bubble that I built from a VSS. But due to its odd shape, there was no way to terminate the bubble cleanly at the top. So an irregular hole is at the very top. I sliced the top just slightly larger than the hole with a cut so that at least the irregular hole was 2-dimensional. I can fill that hole boundary to make it a flat surface, but so far have not found a way to create a smooth patch to satisfactorily follow the bubble tangencies all the way to the apex of the bubble. In other words, I thought maybe I could apply a freeform blend to the flat surface, but the problem there is that the freeform surface that results does not terminate on the irregular hole boundary; it becomes a warped mesh rectangle instead that floats over the hole.
I also tried Edit>Extend, but that only allowed me to extend the bubble surface about .2 inch. My hole is a good 1 inch across.
Is there any procedure that works to fill up irregular (or even symmetrical) holes in geometry in ProE? A mesh would be fine I suppose, but at least a mesh whose boundary points land on the hole boundary.
Thank you very much,
treddie





RE: Patching a Hole
(a useful tidbit to tuck away for future ref).
Trim your opening so you have four edges / sides
(2 U or first direction, 2 V or second direction,
adjacent edges cannot be either tangent or
anti-tangent; for what I'm imagining your shape
looks like projecting a rectangle should work
well) and Boundary Blend.
> freeform blend to the flat surface ...
> a warped mesh rectangle instead that floats over the hole
A Fill surface with an irregular boundary creates an oversized
rectangular (maybe skewed) surface and trims it to the boundary.
RE: Patching a Hole
Thanks for responding.
When you mentioned the square cut deal, and NURBS always having 4 sides, the first thing that went through my mind was "Boundary Blend" which you went on to suggest. I kept thinking I would have to make in the least, a circular cut, so I wasn't thinking Boundary Blend, but who cares? Square is just fine. So I thought, "That's it!" and went to work only to have ProE spit in my face. Because ProE "seamed" the helmet shell into 2 pieces, where the sides of the square cut across those seams, ProE would force a break in the edge of the square for that direction; one direction always worked, but for the other direction, it kept wanting to break up those boundaries into 2 segments each. So I thought, "no problem...I'll just have two attached curves for each side of the hole for that direction". But then ProE keeps saying the curves don't form a continuous loop and fails regen. I then rotated the square so that I could force 2 opposite corners of the square to land right on the seams, because that's where the curves were being broken in two. But it failed again, because one of those corners didn't ALIGN with the seam; it was off by a hair. Need to get to bed and tackle this tomorrow.
RE: Patching a Hole
Sometimes that's the best deal going. ;^)
Sounds sorta like what you need to do is project your VSS seam
edges as Sketcher Reference entities and align trim curve
definition vertices (end points of your Sketcher entities) on
them. Neither the trim definition sketch nor the resultant quilt
trim needs to be strictly 'regular' (i.e. perfectly rectangular)
though keeping it as simple as possible is usually best;
intersection of adjacent edges square +/- 20 or 30 degrees so
blend isoparms don't get bunched up or adjacent continuity
constraints have to fight one another. Nor do the edges have to
be straight but avoid radical curvature fluctuations. Following
isoparm flow is often advisable (your analysis tools; Offset or
Curvature graphs will indicate flow).
Could be, as well, that you can create Datum Points on the seam
edges, Datum Curves from those (either free space and pull back
to surface or constrained (isoparm flow is important) to
surface.
If you can't get something going post the model or neutral
format translation somewhere (here? mcadcentral?) so someone
that's interested can see what you're working with. May be you
need to create the base quilt differently to get a 'nice' shape.
-Jeff (using wf2)
RE: Patching a Hole
Which brings up a point. Is there a way to make a datum curve out of a feature edge, quickly and painlessly? I've tried searching for a way but there is nothing like "Make Datum Curve from Edge" or anything like that which I find truly odd.
RE: Patching a Hole
But to get that seam into sketcher as a reference and do the B-Blend, I had to:
1. Thicken the surface first to give me a physical edge to click on.
2. Publish the Thicken feature, then CopyGeom it back in to break any existing refs.
3. Delete the original Thicken and Publish features.
4. Use the edge from the CopyGeom'd feature as Sketcher ref via Sketch > Edge > Use.
5. Delete the "physical" edge in Sketcher while leaving its ref.
6. Build the 4-sided cut.
7. Publish the new cut surface.
8. CopyGeom it back in.
9. Delete all pre-existing surfaces, leaving only the final one.
10. Doing the Boundary Blend, and presto/changeo! Perfect patch completed.
I might add that I am a saving fool so that I can always go back into the history if I screw up somewhere.
So that concludes my 10-step plan for people with Post-ProE-Traumatic Stress Disorder (PPTSD).
Thank you very much for your help jeff. Without your assistance I would still be blubbering my way through this.
<treddie
RE: Patching a Hole
those hoops, though. If you can read WF2 and want to look at a
helmet-ish shape ...
htt
RE: Patching a Hole
I think that in my situation, the problem was more difficult because rather than building from scratch, I had to reverse engineer this helmet (an Apollo space suit bubble helmet for a book project I am working on). To go back to the beginning, I essentially had only three choices to approach the helmet:
1. Scan the helmet with a 3D scanner which would have cost me $15,000 to $30,000 to buy the scanner (actually found one now for $2500 w/ .005" acc. which will be my approach next year).
2. Build an elaborate mechanical measuring jig to locate individual points on the shell
Surface.
3. Rotate the helmet in 10 degree increments and take digital photos of each turn, with the camera as far back as possible (w/ zoom all the way out so that the helmet fills the frame).
Method 3 was the approach I had to go with due to the cost of Method 1 and the time I had with the helmet shell, but has two problems:
a. Unless the camera is infinitely far away from the subject, true orthographic projection is impossible (there will always be some perspective distortion).
b. Unless you have a very special lens, there will always be some lens distortion in the field of view.
c. Grabbing the helmet cross-sections in this way has varying degrees of accuracy depending on its shape (see attached file Bad, “Helmet XSections.pdf”). If the helmet had the exact same cross-section no matter which angle it faced the camera, Method 2 offers a pretty accurate method of reconstructing it. However, per the discussion in the attachment, if the helmet has different cross-sections for each rotation, then the cross-section that the camera sees is NOT a crossection through its rotation axis. In fact the camera’s “cross-sections” are not flat surfaces at all, but “serpentine”, 3D surfaces. In my case, the only two reasonably accurate cross-sections were from the side, front, and back views. Fortunately, this helmet does not diverge TOO much from ideal, so that even though the cross-sections were not true 2D sections through the rotation axis, they weren’t too inaccurate.
Thus, I was really forced to rely on using the camera “crossections” as trajectories for a VSS. The result was faithful to the original, just not THE shape (see .jpg in the zip file). If you built a bubble from my ProE model and put it next to a real one, I think you would be hard pressed to notice the differences. The differences would be most noticeable only if you compared actual true crossections from both.
Don't know of any other way I could have approached this, but learning of a cleverer way would be nice.
RE: Patching a Hole
> from scratch, I had to reverse engineer this helmet
Indeed. Interesting project and a novel approach.
For what little it may be worth, I wouldn't have done it that way
although I might do something similar for 'supplemental reference'
data, nor would I scan it the way most(?) people would envision
going about it. That's predicated on [1] the assumption that there
are three key features (the lock ring and two 'conicoids',
probably ellipsoids) you want to capture, define and blend, and
[2] the shape definition rule of thumb; less is better.
Many objects are not so 'freeform' as we might think. Where they
are not; if we can identify the general nature of the shapes we
can capture, by whatever means, the important curves. The rest
will come naturally and can be verified with the 'supplemental'
data, assuming it's accurate enough to be more than a source of
confusion. That is especially relevant if the data is going to be
used to manually model the objects without the surface fitting
algorithms in the more expensive reverse engineering software
suites.
There are a few people that frequent McNeel's Rhino forum using
less expensive digitizers and software. Might be a decent place to
dig around or seek advice.
> for a book project I am working on
Cool. Something I might be interested in? ;^)
RE: Patching a Hole
A very long and tedious proposition.
I like your idea about simplifying the helmet to basic primitives and working from that, but it is extremely difficult to figure out what those primitives are when you have this freeform shape in your lap and no way to know just how those primitives "land" on the shape. There are no reference points to measure anything against. But also, this helmet shape was designed in the mid-sixties without computer graphics, so I imagine the master was hand-crafted by a really good craftsman, perhaps from bare-bones details about what was required of the shape. What would be your judgement?
The book project is a thing I started back in 1998, and covers Apollo spacesuit development during the 60's-70's. Mostly a very detailed illustrated account of how everything worked and was assembled. I have essentially finished reverse-engineering all of the hard components for the ILC A7L/A7LB lunar suits (which pretty well covers most everything back to the A5L (1965), by disassembling/measuring each part.
Why space suits? The reason is that my BIG goal was to do pretty much a similar thing with all of the Apollo hardware, spacecraft, launch vehicle. When trying to figure out a good starting point, I figured that the spacesuit would be the "easiest" project to tackle first. Although I still think that is the case, I must say that the old saying that anyone wanting to write a book doesn't know what they are getting themselves into is certainly true. I knew that going in and was prepared for it, but you can't REALLY appreciate what it means until you're in the thick of it.
The book will cover the ILC/HS line back to 1959.
RE: Patching a Hole
> extremely difficult to figure out what those primitives
> are when you have this freeform shape in your lap and no
> way to know just how those primitives "land" on the shape.
True. It's very often not easy; trying to second guess the original
definitions, usually devolving into experimenting with what seems to
make 'sense', trial and error approximations. What you're really
looking for is uninflected areas, max and min curvatures and rates.
> imagine the master was hand-crafted
Good point. Really, though, it doesn't change a lot. You should (or I
would) still break the shape down into sections that could be
approximated with analytic shapes or shapes with similar characteristics.
You'll still have to fit and refine curves, but fewer of them, and the
discrete surfaces can be tweaked and refined to adjust local curvature
and rate of change.
The attached file has a couple of 'rough draft' variations on what I
imagine the shape to be. The Boundary Blend group may be something
you can incorporate into your existing model (create a new 'cap',
blend between it and the lower portion of your surface). If you can't
get something you think is acceptable and can let me have your wires
I'll see if I can't whip something up.
> The book project
Well, that is interesting and quite an undertaking. You have to
really love the stuff. ;^)
RE: Patching a Hole
I did take a quick look at it though, and it dawned on me that maybe the reason I'm getting bunching in the top third is that sections at 10 deg. intervals may be a little too much for ProE to handle gracefully. Maybe if I backed off to one section every 18 degrees (5 sections per 90 deg).
At any rate, it seems ridiculous that ProE can't just create it's own "hidden" closed spline for each step up the central origin trajectory. Since each spline would be completely convex, I don't see why it wouldn't work. Bunching seems stupid to me.
At any rate, I quickly checked out what looked like notes for a relation in your file. I'll take a closer look tomorrow.
Attached is a Maxwell rendering of the bubble. You can't really see the bunching issue in this image due to the angle of view, but it's definitely there.
RE: Patching a Hole
Please note, I'm using the term "isoparm" rather loosely here. There isn't really much "Iso" going on in radial crossections, I suppose.
RE: Patching a Hole
But, I'm not going to add more cross-sections for the very reason that I could only hope to diminish the problem, not remove it entirely. And who knows what ELSE would crop up, after adding more secondary trajectories.
Since this is a reverse-engineering problem, I feel it is important to stay faithfull to the original design, and trying to find the primitives to build it from will only add error, since these primitives could only be approximations based on assumptions about the true, radial cross-sections. The only way to get true cross-sections of any orientation would be to spray coat the helmet with a non-reflective coating and put a laser to the helmet. But then we're back to 3D scanning. What I WOULD like to do is 3D scan the bubble, and slice through the surface model in various ways and look for accurate primitives based on the sections. Fortunately, I have time to play with this thing; I can always work on other parts and wait to get back on site and scan the helmet later.
For the time being, I am going to try a rotational blend and see what happens.
<treddie
RE: Patching a Hole
Unfortunately I don't think you'll find much relief there. The problem is the curves. There are only a few ways to get ideal curves; i.e. extract them from an ideal surface or define them with the same mathematical function that would be part of the surface's definition. Free hand doesn't work for the average person using average tools. Tracing scan points only works well if the scan is close tolerance and the scan line corresponds to a natural isoparm flow for the surface (not a problem with shapes as 'regular' as the bubble but important for more intricate shape combinations). Increasing the frequency of nonideal curves just increases the frequency of the waves which may further degrade the surface's appearance, and given the right circumstances can actually increase the wave amplitude. Thus the 'less is better' rule of thumb.
Just as an FYI: An isoparametric curve; a.k.a. isoparm, is a trace of a constant surface U or V value. All surfaces have them and, like points on a line, they are infinite in number. I suspect what you are referring to as isoparms are visible curvature irregularities. There is a relationship as irregularities are induced by control vertices and knots which also define the isoparm values (or maybe it's vise versa if you want to be mathematically correct; there are relationships anyway).
Good luck with it.
RE: Patching a Hole
Sorry for the rant...I guess I'll never get used to living in a world that could have been built on excellence, but instead is predicated on how long it is 'till the next coffee break.
About the isoparm thing, I was referring to radial sections as isoparms, which is not really isoparm-like except that the sections I have are rotated in equal increments. Unless (U) could be thought of as equal longitude and (V) as equal latitude. But that doesn't really classify as isoparms, I suppose.
Anyhoo, I'll be examining your file to look at things from a different angle. Hopefully it will restart my brain.
RE: Patching a Hole
I resist the primitives idea, only because I am not starting a helmet from scratch, but rev-eng'ing it and keeping it as accurate as all the other parts I have already built models of. At .005" accuracy, I hope the scanner I'm looking at for next year will deliver a mesh that holds up when textured as a refractive/reflective surface. .005" error is still a hill or valley on a surface, and hit obliquely with light may still show problems, or bend light in an obviously wrong manner. Also, a company may SAY .005" accuracy...but under what conditions?
So,...I still haven't taken a close look at your file since I was so busy edumucating myself about different blend attempts. At least now I know from experience the limits of Sweeps and Blends.
RE: Patching a Hole
RE: Patching a Hole
You might find the attached interesting to play with.
I don't know how hung up I'd get over accuracy with that thing. It's a stable shape but it is plastic. I'm thinking a thirtysecond to sixteenth inch from concept ideal after tooling, process, age ...?
RE: Patching a Hole
1. Deformation due to heat when released from the mold.
2. Repeated press/depress from 0-3.8psi during normal use, plus proof pressure to I believe something like 16 psi.
3. Age, roughly 40 years old.
I don't know the stability of polycarb, but the stuff IS quite flexible.
Here's another weird coincidence. 2 months ago, I was drawing up plans for a model of the Planet of the Apes spaceship (to be built out of styrene sheet, eventually). I have copies of the original blueprints used to build the full-size prop. But like all things, and especially in the movie industry what with the time crunches and all, the elliptic cone crossections did not come out quite ideal, and the prop ended up with slightly bloated ellipses (imagine a cold capsule shape, then imagine an ellipse with a tiny bit of capsule shape distortion added to it). So that caused me to recall something from my old days as a technical illustrator in the 80's, something we used to refer to as a poor man's ellipse. Sometime's it is faster to build huge ellipses that way, rather than scan in an ellipse from an ellipse template, blow it up in the camera, and use it as a pattern. Remember, POA was back in the 1960's and there were no computers OR scientific calculators, and I seriously doubt that Hollywood would have spent the time plotting ellipse points via slide-rule and trig tables. The thread and tack method is too flexible for large ellipses, so any number of "poor man's ellipses" would have sufficed. At any rate, this prop had that kind of tweaked elliptical shape to it. My problem was that since I was building a computer program to build cuts through this type of cone, so that I could eventually build flat patterns for styrene sheet, I had to find a way to tweak the standard elliptic cone equation to handle the error in the ellipses, and still simultaneously solve for intersection with a free line. If it's an ideal elliptic cone, you end up with a quadratic for the simultaneous solution, and it is simple to solve analytically. But I had to add a deformation filter of sorts. What started out as the simple ellipse (and elliptic cone) equation ballooned out into these really huge equations, especially since now, this new tweaked cone still had to simultaneously solve for intersection with the free line. What I ended up with was a numerical solution.
So here I am now, looking for an ellipsoid to base the helmet on. From the side, I get a beautiful match with a certain ellipse. From the front I get...a poor-man's ellipse! Even with age and deformation, I assume the new helmet would have still had this shape because the error from ideal is too great (overall, about 1/4 in). But my point is that, I haven't thought of poor-man's ellipses in decades, and here come two projects one right after the other suggesting their use.
Weird...
So anyway, now that I have the general equation for the tweaked ellipse in hand, I can plug this into ProE through a relation and build the funky ellipsoid primitive (2 planes tweaked, the third is an ideal ellipse). The only thing yet to plan is the transition down from the tweaked ellipsoid to the circular base, then add a base ring. That would be simple, since I can grab the shape of the top section of this transition from a section through the ellipsoid, use 4 datum curves to control the transition down to the circular base, and I think that's it.
Opened your file, and looks like I'll have something to play with tomorrow. Am curious about what you did in there, since it has bearing on the whole inaccuracy issue.
Thanks again, Jeff.
<treddie
RE: Patching a Hole
Computers...I love 'em...I hate 'em.
RE: Patching a Hole
Helmet almost completed. That transition section is a bear though. Am getting good results in terms of tangencies and good clean surfaces w/o bunching, but not enough secondary trajectories to control the form as it transitions from the ellipsoid down to the circular base ring. Nice clean sides but the front and back need a couple more control curves. I hope tomorrow is THE DAY.
RE: Patching a Hole
It's finally done, almost. Very sweet surface with no imperfections. Your primitives idea was the way to go. I really didn't think I would find a good primitive to work from. But it's pretty obvious it was an ellipsoid. The majority of the time was taken up by the fact that I had scaled my import curves incorrectly before using ProE, so I spent all day today rescuing the file I had been working on, replacing references and importing new curves.
Then, I simply could not get the ellipsoid to thicken along with thickening the transition area down below, without a ton of regen errors, so had to trial-and-error until I found the solution. But it is a partial solution so far. The ProE model is great, but the Wavefront model I export ends up with a seam between the dome and the bottom half. Looks like the two did not join together as one part.
Which brings up the point. Is there no way at all to thicken imported geometry? If I could do that, half the problems would be non-existent. But for some reason, ProE can't handle it. I can import a beautiful helmet surface into a new file, but can't thicken it. That had me scratchin my head for about 3 hours, trying to find a work-around. Just seems weird that ProE can render a surface (which means it understands its geometry), but can't thicken it. Weird.
RE: Patching a Hole
RE: Patching a Hole
Failure to Thicken (or Shell) almost always is a result of [1] inability to create a surface normal offset, usually min rad of curvature related or [2] inability to extend or re-trim, if necessary, the offsets and join the edges.
Native or import; makes no difference. The same rules apply.
Surfaces with singular edges are always suspect and should be checked, not only discretely but in conjunction with adjacent surfaces.
RE: Patching a Hole
But in terms of looking for a solution, I wondered if cutting out the midsection to either side of the joining of the two surfaces (as meshes) would allow me to put in a small transition mesh to connect the two. There will still be a lack of consistent curvature there, but at least it won't be a nasty edge. At any rate, even though I've been using ProE since about 1999, I've never really been faced with organic shapes before, so anything I can do to explore the limits of the tools and find out through experience what NOT to do would be helpful here. For instance, this is the first time that I've ever noticed a discrepency in solid vs. surface. Ah, the dirty litte secrets of ProE.
RE: Patching a Hole
A surface edge is defined by at least [Degree + 1] Control Vertices. If all the CVs defining an edge are coincident the edge is singular. I think there's actually more to it than being coincident; e.g. there is a "singular point" entity created. Pro/E calls these "degenerate edges", I think, but in my mind (and in 'Rhino speak') that's the description of another problem causing condition; adjacent edges of a surface meet at zero degrees (they're tangent to one another). Regardless of what you call them keep in mind that the problem potential is high.
> ever noticed a discrepency in solid vs. surface.
> Ah, the dirty litte secrets of ProE.
I hope we've put that to rest as a misconception. Since it's related, rather than going back to the other discussion:
> "one-sided" surfaces in programs like
> Lightwave or 3DSmax (infinitely thin)
... ... ... ...
> Not that the quilt is necessarily made up of
> surfaces, but that the surfaces are additional
> information along with the quilt description.
> Is this the two-sided thing that's going on?
> I really need to find a good book that explains
> what ProE is doing at that level.
Without getting mired in the nuances of one program's or the other's terminology:
[1] All surfaces are 2D objects, having Area only (infinitely thin).
[2] All quilts are made up of surfaces, one or more. Quilt is a data container for the surface(s), associated edge attributes, etc. analogous to IGES or STEP "shell" objects (not program Shell Features). When adjacent surfaces are joined (Merged, in Pro/E) the individual surfaces' coincident One Sided edges are replaced by (single) Two Sided edge entities (meaning the edge is bounded on two sides, I suppose).
[3] All Solids are closed quilts, again a data container for the quilt(s) and additional attributes that may be associated with a 'solid' object. When you create a 'solid' feature you're creating [1] and [2] above along with all the necessary boolean operations, etc. ... all with a single button push ... amazing, huh? ;^)
Coming back to this discussion:
> in terms of looking for a solution
Can't offer anything specific without examining the geometry and trying one thing or the other myself. For sure; trimming back on either side of an unsightly edge (mismatched position or dihedral angle or a tiny wrinkle?) and blending to fill the gap is a possibility. Success will be contingent upon bounding edge quality, tangent directions, curvature if a G2 blend and if a poorly structured surface is the reason for the existing nasty edge ... it's a coin toss.
RE: Patching a Hole
I just went through an unsuccesful session trying to blend the two gap surfaces together but no go. Just two "simple rings, really. But "simple" appears to be a misnomer. The top ring is a surface pulled from the ellipsoid cut. And the bottom ring is spline based. They don't like each other. In fact, I think they HATE each other, like Tibet and China. I might try to redraw the top curves as splines to get them to become more friendly with the bottom curves, but that just means more chances for mismatching at the top.
Tried CADfix, but no luck there either.
I'll try some more things tomorrow and if those don't work, I must admit defeat and send you a file. I wouldn't be trying to make this thing so "perfect" if it weren't for the fact that it is a clear, refractive object, and any unwanted seams really show up, even if they're just .005in wide. Actually, I blame nature for being so anal. Couldn't God just throw in a little more quantum fuzziness into light refraction?
RE: Patching a Hole
Will try exporting out as a mesh and re-importing that into a new .prt file and gap-cutting/gap-filling there. This is one of those things where I can't stand losing. Going to exhaust all options.
RE: Patching a Hole
Here is the jpg I forgot to upload.
RE: Patching a Hole
It's locked . If it appears not to be it's a graphics issue.
It's hard for me to imagine how you must be going about this, especially when you start talking about importing and exporting meshes.
The attached (WF2) file demonstates how I'd probably attempt to transition between the two 'foundation' shapes.
RE: Patching a Hole
Thanks again for the download. And once again, my ignorance is showing when it comes to modelling fluid, organic shapes. The power of the Boundary blend you have demonstrated in the last file really shows its power beyond simple patches. Now that I see what's going on, I agree with you that the Bblend is the way to go.
But please check the attached images. You'll see that your file has the same problem I've been having. It's that seam where the dome does not quite match up with the Bblend. And it's real (it's not a display issue) because when I export out as Wavefront .obj, those pesky things are actually there and they end up in the resulting mesh (3rd image shows imported file in MaxwellRender). And the frustrating thing is that even though the artifact may be only .001" wide, when I do a high-res ray-traced image of the bubble, it shows up clear as a bell (it causes its own refraction). Thus, like what many people do, is they'll take their image into Photoshop and retouch it out. But I would rather not have to worry about that if I can avoid it fairly easily with some procedure in ProE.
RE: Patching a Hole
> image into Photoshop and retouch it out. But I would
> rather not have to worry about that if I can avoid it
> fairly easily with some procedure in ProE.
Looking at the noted edge...
_ max deviation is < 4 E-4" (Rhino has a nifty function, shown in attached)
_ max dihedral angle 0.05° (Pro/E analysis function)
_ curvature and rate continuity are very good (Pro/E analysis function)
I have no interest in rendering software, don't know anything about it, but I believe all that's needed is a proper meshing. From Finite Element modeling I know that the mesh vertices on each surface should not be offset with respect to one another along that edge. The surfaces are being meshed individually rather than as a quilt. If the Two Sided edge is being reference by the mesh generator instead of individual One Sided edges the vertices would be coincident and the seam closed. I suppose a render mesh would live by the same rules.
Also in the attachment is a rather coarse Rhino generated mesh. Don't know if it'll help any with evaluating the nature of the problem, but fwiw.
RE: Patching a Hole
But that could be easier said than done, especially with complex shapes where ProE determines where the edges get made. For instance, the edges of the quilt surfaces for the ellipsoid are determined by ProE and I'm stuck with that (unless I cut the ellipsoid somewhere into 2 separate pieces to define new edges). So if I want a boundary blend for the transition area, then any control curves I build should originate (or terminate) on ellipsoid, surface edge endpoints. If I catch your drift correctly.
What I find interesting is that, it seems actually an almost irrelevant problem for actual manufacture; if a master were tooled from my file, it would probably be sanded and prepped anyway before molds were made. The problem would be "erased" by old school methods. But from a 3D rendering perspective, it's a bear of a problem. The edges HAVE to be repaired digitally. It would be SO nice to have an elevation map superimposed on the quilts where you could tell the program, "remove any deviations from the local 'zero-elevation' in this area.", by circling the area with a mouse selection, or by circling it and by using an eyedropper tool to pick the color of the elevation you want to match to.
Thanks for the Rhino image. I'm very new to Rhino, so I have a lot to learn there, too.
RE: Patching a Hole
> all surfaces in ProE have control vertices coincident ...
Corner vertices should be coincident within system tolerance or less, as should be the edges. Do not confuse NURBS Control Vertices, which will be coincident with the curve they describe at end points only (assuming end point only full multiplicity knots, but let's not go there), with Mesh Object Vertices.
> ... in order to always have single 2-sided surface edges.
No. Two coincident One Sided edges do not equate to a Two Sided edge. Individual One Sided edges, though coincident, can be parameterized differently resulting in mismatched mesh vertices. A Two Sided edge is a distinct database entity created when two coincident surface edges are joined (Merged).
[One-Sided and Two-Sided edges are formal Pro/E entity descriptions, btw. You can Search for them by Type.]
> ... that any exported meshes don't have nasty
> 1-sided edges, and therefore gaps.
I don't know that's true. Two Sided edge definitions can exist but be ignored by the mesh generator, by choice or by 'bug'?
> But that could be easier said than done ...
> ...unless I cut the ellipsoid somewhere into
> 2 separate pieces to define new edges). So
> if I want a boundary blend for the transition
> area, then any control curves I build should
> originate (or terminate) on ellipsoid, surface
> edge endpoints. If I catch your drift correctly.
Not necessarily, though usually 'good practice' and simply makes 'sense'. Consider two offset planar sketches, each a line segment with tangent arc. On each sketch the line and arc endpoints are coincident at 0.5t composite. To blend between the two sketches you can create second direction curves at, for instance, 0.0t, 0.3t, 0.7t and 1.0t. A piecewise blend will create a two surface quilt with a Two Sided edge at 0.5t. You can also omit the 0.0 and 1.0 curves to create a blend that spans 0.3, 0.7. ~If~ the first direction curves were surface edges instead of (our planar) curves, when the blend is joined to the original surfaces the original surfaces' edges will be 'split' to coincide with the blend edges.
To go off on a tangent regarding trimmed surfaces; it's important to make the distinction between a surface edge and a trim edge. They share a common set of rules and assumptions but are not equivalent; e.g. a surface by definition always has four edges but can have a trim boundary with an infinite number of edges. Singular surface edges are problematic. Two or three sided trim boundaries present no problems.
> The edges HAVE to be repaired digitally.
Am I incorrectly assuming the only problem is an inappropriate meshing of the modeled object (referring to the model I posted, not having seen your model)? If we're talking about other problems (high frequency, small amplitude waves, etc.); it's always been my assumption that the inherent 'averaging' nature of meshing and subsequent mesh manipulation can cover a multitude of sins whether done for manufacturing process or rendering. Incorrect?
> new to Rhino, so I have a lot to learn
Time spent learning it is a good investment. The 'low level' entity access and good documentation can teach a lot that will demystify much, if not most, of what happens behind any 'high level' user interface program curtains.
RE: Patching a Hole
Was examining your 3rd download, and have been examining what you did to make sure the BBlend saw tangency with the ellipsoid. I believe the problem I'm having is there is no way for ProE to know that I want my BBlend tangent to the ellipsoid because there are no explicit refs to it. It looks like you did a fair amount of preliminary stuff to establish tangent refs for the BBlend. In other words, your BBlend is based on curves whose descriptions were built from tangent features, so the refs were inherently there. With mine, ProE doesn't even see what I want to be tangent to, so it fails. Would be nice if ProE could allow you to just select the tangent surface and go. I'm particularly interested in that projected curve you through in there, as it appears to define the top edge of the BBlend.
Since my model is in a major state of revision, I am going to redo the transition area before I go any further.
By the way, one of the problems I was having was that even though I could regen a successful VSS, there nonetheless was a skrewed-up spline for a trajectory. I found it through GEOMcheck. How it got that messed up, I don't know, but it would not regen for Intent Manager, so I rebuilt it. But now these trajectories need to be made explicitly tangent to the ellipsoid. So those are my duties tonight.
Again, thank you very much for all your help. I'll give you an update when I get the successful BBlend.
RE: Patching a Hole
RE: Patching a Hole
Spent a lot of time figuring out how to get tangencies that the BBlend would accept. My curves showed the proper tangencies, but they were to a base curve that was made by Edge > Use in Sketcher. So I did what you did which was to use a projection of a line instead, onto the circular base.
That solved it.
Hopefully I will have a solution tomorrow. Need to think about getting good transitions between the high rates of curvature on the front/back relative to the very straight sides.
RE: Patching a Hole
Just about completed. I made a number of simplifications and created better constraints, pretty much following your approach in your 3rd download. I used your idea for a projected curve onto the ellipsoid to trace out the top BBlend curve. Before, I had just made a simple horizontal trajectory around the "waist" as my top curve, but the problem with that was that all of the tangencies had different slopes along that edge, so ProE would have a fit and do the best it could. So I decided to make sure that all of the slopes would be 90deg vertical drops at the top of the transition area, along the new edge. That's where the trick you employed where you can get a line to follow a curve's edge really became indispensable; it allowed me to find those points around the tilted ellipsoid where the slope of curvature was exactly 90deg. I connected those points to get the top curve and that completely eliminated any mismatching across the top. Have rendered a test and found some areas I want to clean up around the base, but it is 99% there. Purely cosmetic issues now, since I still had to add 3 trajs for the back portion of the helmet side, and 3 for the front portion to get the BBlend to not "dip into" the ellipsoid. Those trajs had hand-drawn splines in the middle parts of the curves and they just need a bit of curvature adjustment. I will post my final results here soon.
RE: Patching a Hole
Here are some screen caps of the finished polycarb bubble. The last image has the unfinished neckring attached. Still a lot of work to finish the helmet assembly; internal headrest/vent plenum, feedport that attaches to the hole on the side, 2 label plaques on the ring, epoxy line on both sides of bubble thickness at the ring, and various engraved markings. The headrest will be interesting because it has a shape that follows the internal shape of the bubble. Now that I have the bubble surfaces, the biggest milestone is passed, and the headrest should be "easy" to conquer.
You'll notice an intentional seam I put in for the mold line.
Thank you very much for all of your help. You got me jump started on surfacing, so I don't feel AS intimidated by it as I used to be. Huge learning curve. I still need to go back and take a look at some of the other things you had going on in your files. Particularly, the Bezier surface work.
Am rendering an image of the helmet, and the surface looks awesome. When everything is completed, it 'll be killer.
Thanks again for all your help. You were a major factor in making this a success.
treddie
RE: Patching a Hole
RE: Patching a Hole
Here is an unfinished rendering test of the helmet and ring. Still hasn't rendered long enough to eliminate the noise.
RE: Patching a Hole
RE: Patching a Hole