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Old Nov 20, 2009, 02:27 PM
Sink stinks
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Originally Posted by Curare View Post
In rhino I use the Osnap menu. It's generally at the bottom
you tick boxes of whatever you want to snap to and it uses the smart cursor method where you can scan over an object or curve and it will tell you what it can snap to.

Takes a little getting used to but once you're rolling, it's easy.

Heres some of my work.
I knew about the Osnap menu, I was just saying I wish there were some hot keys so I didn't have to move the cursor back and forth between the drawing and the menu all the time. Believe me, it saves a lot of time. With TurboCAD, you can leave all the snaps off and then use them as you want them by just pressing one key.

I did realize that you can move the Osnap menu and undock it from the bottom of the screen. This would probably save some time.

I'm going to keep messing around with the trial version and see if it's worth buying the full version on a student discount. I'd keep TurboCAD around too, in any case.

Nice models, by the way.
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Last edited by Montag DP; Nov 20, 2009 at 02:34 PM.
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Old Nov 20, 2009, 04:34 PM
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Hotkeys for snapping would indeed be very useful. I will write to McNeel and request that they include this feature in v5--when I think of all the time that I save in Photoshop and Illustrator using keyboard shortcuts it makes perfect sense to implement more and/or user-definable strokes for working in Rhino; I completely agree that having to leave your workspace to toggle which snaps you want is a bog when you're focused on drafting and have to swing out of the workspace to check a box, then refocus on what you were doing.

C
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Old Nov 20, 2009, 09:35 PM
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ptxman,

Here's how you could make fillets for your F5D sample. Note that I didn't take the time to perfect these lines so the upper fillets are not 100% tangential to the fuselage section, but it could be achieved by trial and error (I got damn close on my first guess using 3-point curves on the back and five-points on the leading edge) or by adding additional cross-sections for the sweep2 command to interpolate.

The process is a combination of what I described earlier--projecting curves, enlarging a root section, drawing your surface edges and then sweeping or curve-networking your leading-edge and trailing-edge arcs.

Note: This is not a fast process since you have to manually build the surfaces from curves that you create, project and refine.

Carl
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Old Nov 20, 2009, 10:24 PM
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I would suggest that you will get much better surfaces if the fillet intersections do not “pinch”. This will not create a constant radius fillet but that is not what airplanes have in these situations. The fillet radius WILL change radically, especially at the top center.
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Old Nov 21, 2009, 02:28 AM
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That's an interesting idea, and could be made to work with manual cross-section placement. It's moving more towards a fully blended surface than a fillet, so I suppose it's up to the designer's goals if that much more surface area needs to be created, or if a standard fillet is enough to lower interference drag.

Definitely worth playing with in my opinion, if for no other reason than to tack another technique to the belt...

C
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Old Nov 21, 2009, 08:33 AM
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Some sort of generic diesel

..for filling those empty engine bearers.
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Old Nov 21, 2009, 11:49 AM
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Originally Posted by allanflowers View Post
I would suggest that you will get much better surfaces if the fillet intersections do not “pinch”. This will not create a constant radius fillet but that is not what airplanes have in these situations. The fillet radius WILL change radically, especially at the top center.
Thanks, this is great stuff! I recall arriving at something similar to what you guys have shown. I made an offset curve of the root rib & projected that on the fuse (like red arrow curve). The (blue arrow) curves looked pretty similar, it tied into the TE dart radius that goes back to the fuse. On the LE I think I split it on the airfoil, 0,0 coordinate or else something bad happened trying to warap around...

Anyway, its at this exact point with (Ill call them rail) curves established I seem to spin my wheels in the mud trying to make the actual fillet surface.
- do you start by making mini section curve(s) along these rails like example shown & sweep a surface using both sections & rails?
- or do you use only the rails (no section) & start surfacing with network or patch type command & diddling the bulge settings? (Whenever I tried this it always bulged in the wornk places, I got the impression it needed to be guided with section curves).
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Old Nov 21, 2009, 12:49 PM
Sink stinks
Montag DP's Avatar
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Quote:
Originally Posted by Haole View Post
Hotkeys for snapping would indeed be very useful. I will write to McNeel and request that they include this feature in v5--when I think of all the time that I save in Photoshop and Illustrator using keyboard shortcuts it makes perfect sense to implement more and/or user-definable strokes for working in Rhino; I completely agree that having to leave your workspace to toggle which snaps you want is a bog when you're focused on drafting and have to swing out of the workspace to check a box, then refocus on what you were doing.

C
Yes, hot keys for the snaps would definitely speed things up. Though, because of the way the snaps work it's not absolutely necessary. With TurboCAD, when you have a snap activated it won't let you click a point that is not a valid snap, which is why it's best to leave the snaps off and use the hot keys most of the time. Rhino would still definitely benefit from it though.

I've been playing around with Rhino a lot the last couple of days, and the more I use it the more I like it. It has a lot of really nice functions that TurboCAD lacks, plus I just like the workflow in general better. It seems to me like Rhino was based in 3D from the start, whereas TurboCAD started in 2D and has transitioned to 3D. As such, working in 3D seems more natural in Rhino.

I've been converting this new aerial photography design from TurboCAD to Rhino manually the last couple days to get used to the software (with the evaluation copy).
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Old Nov 21, 2009, 02:03 PM
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Quote:
do you start by making mini section curve(s) along these rails like example shown & sweep a surface using both sections & rails?
You would do exactly what you show in your second attachment--many cross-sections will be needed to keep the surface tangent to the fuselage and to the wing over such a large blend. Use only 3-point curves and editing the surface control points will be easier for the finishing touch.

Also, as a rule, just work on one side of the model, then mirror your work over to the other half when finished. Or, use symmetry to keep your rails drafted tangent as they pass over the top of the wing and fuselage so that there will be zero visible seaming in the middle of your surface.

After all the time that we've all spent fiddling with filleting, I'm starting to wonder if somebody out there has written a definitive tutorial on the subject ...time bust out the google-fu.
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Old Nov 21, 2009, 05:39 PM
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I couldn't find any definitive tutorials that show easier and/or better methods for doing this. Maybe Harpye or a lurking Rhino expert can chime in?

Anyways, I'm downloading 11/17/09 WIP build of Rhino 5 64-bit to see how it handles this problem. I didn't see any mention of improvements for this specific issue but it can't hurt to take a peek.

C
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Old Nov 21, 2009, 05:43 PM
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Originally Posted by Haole View Post
... I'm starting to wonder if somebody out there has written a definitive tutorial on the subject...
Well if you ever locate something, please let me know. Ive seen many stunning, rhino based objects with complex filleting, proof that it can be done, some-how, some-way. I get the feeling the technique is not a definative procedure, maybe more situation dependant.

Ive searched rhino's newsgroup, which is a great resource btw, for issues & solutions pertaining to filleting. Usually the pro's there can recommend a workaround or suggest what might be causing problems. Others who have experience with other programs seem to feel its still lacking in certain regards. Ive never run solidworks or other programs to be able to compare. If they did a better job, Id be tempted.

Another rhino technique Ive seen examples of is where they use the intersectiion line of 2 surfaces, they then make a circular 'pipe' surface around this line, then cut both the surfaces on the pipe so now there is a constant width gap. Then they blendsurf? (cant recall the command) the gap by picking the edges. Ive seen this on some organic-y models & it looks real good. But applied to models like this example, it seems to again relay on the series of curves along the pipe rails to get teh control your brain intuitively knows is nicer.
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Old Nov 21, 2009, 06:12 PM
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I'm looking through the Rhino 5 wishlist right now and there is already at least one request for a better solid engine to handle complicated filleting operations.

People are asking for a lot of stuff from the developers but doesn't this seem like a crucial feature to get working considering Rhino's prevalence in the naval architecture realm? You'd think people would be banging out faired-in keels and rudders all over the place! How about radar wings or flying bridges? I'm boggled but then again I only know enough about this software to be dangerous to myself

Carl
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Old Nov 21, 2009, 06:29 PM
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Sweet. Have a look at post #7 here.

Seems this maintains tangency and looks stupidly simple!
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Old Nov 22, 2009, 09:12 PM
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The discussion on fillets has me interested. I used to struggle with these things all the time before I retired as a designer at Nissan. I had gotten pretty good with them at one time and thought maybe I should share a little of the process I used to go through. Of course I was/am working in Alias, which has more controls regarding surface continuity but I suspect that a good Rhino modeler can manage to do most of the same things, albeit with a little more manual input and curve fiddling. There are certain principles in building good surface, no matter what tools one is using.
First, a simple constant radius fillet tool result… very fast and often good enough for many applications… but maybe not too good in this situation.
The trim lines it creates wander all over the place, especially at the leading edge of the wing form and at the center of the central nacelle where the fillet is rather pinched. This is what I was referring to in my earlier post. In addition, there is no good continuity from the fillet to the major surfaces. The curvature changes radically, as shown by the color thingy eval tool. The zebra shader is rather a mess too, with abrupt jogs at the edges and wiggles within the fillet. Still, if you are duplicating a scale aircraft – and this is the solution IT used – then this would do just fine.






However, you are trying for something smoother, it is on to plan B – using a freeform fillet and carefully constructed trim curves. The more professional, the better.
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Old Nov 22, 2009, 09:24 PM
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I created some lines to project onto the surface to make better trim curves. I didn’t take a lot of time on these which always turns out to be a mistake but sometimes it is better to plunge ahead and get a “solution”, even if it isn’t ideal (you will probably want to redo it later anyway). One can go back and redo the basic projection curves, knowing better then what you need to correct.

The idea with the projected curves is to make them compatible with the basic form intersections, and to incorporate the general size and taper (if desired) that you want. Sometimes it is good to work with a copy of the intersection line, manipulating it to fit your requirements. A tubular intersection tool often gives a good starting point too. In the final analysis, it is a matter of experimentation and trial & error. Unfortunately, you really don’t know what will work until you struggle though to some solution.
I also decided to break the basic surfaces into sections to get a better chance to control things (usually this is true but not always).

The basic fillet tool, working with the new trim lines and divided surfaces, still didn’t do very well. In fact it came out worse than the first effort because the new trim curves are far more challenging. I am not even showing the result of that attempt.
It looked like a “rail” surface might work so I tried it. Not good. I added an additional generation curve in the middle which helped but still not so good… The isoparms are swimming all over the place, especially near the top. This might have been a case where not working with halves of the basic surface would have actually worked out better by controlling that upper portion. I didn’t go back to try that, though.



Instead I tried the “square” surface tool. I assume Rhino has some kind of decent four sided surface maker.

The “square” tool did a pretty good job. The zebra stripes still aren’t great within the fillet itself but the regular shader rendition looks decent.



Keep in mind that these fillets are bridging across the gap pretty much. One can modify the curves to make the fillet very tight or fairly loose, depending on the character of the curves running that direction – even working with the same basic trim curves.
If I was still on the job and this was my project, I would go back to my projection curves and do a whole ‘nother shot at this thing. I might also try the rail surface approach again,using copies of selected isoparms made with the “square” tool. And whatever other tools available…
However, I am not being paid so the heck with it this time. It is important to try for a solution early but then go back and try any other relevant tool or process. Sooner or later you will get the surface you want. You can use the failures to copy construction curves for the next attempt. I think it usually took at least three shots going through before I would feel satisfied. Of course save the results at various stages so you can go back if necessary.
I hope this helps you some.
Maybe I will pull up some old project images to show if anybody is interested. Otherwise, thanks for bearing with me.
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