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View Full Version : Help to Model Tubular Y shaped junction



WaxSteel
04-22-2007, 09:31 AM
I'm modeling some roof cap ridges and so have got three identical converging Tubular shapes and need to model a "Y" shaped junction to bridge them where they meet over a roof end arch.

I've polygon patched them together from their end cap polygons, but I was wondering if there was a better way of doing this - like the bridge tool but with three bridging polygons instead of two?

SplineGod
04-22-2007, 11:17 AM
Do you have a picture of the junction and does it have to be sealess?

WaxSteel
04-23-2007, 11:18 AM
Well it doesnt have to be perfect in this case because the renders will be quite distant (its for a piece of roofing) , but from a construction method point of view, I was wondering if there was a quicker/ better way to handle complex junctions, rather than laborious polygon patching - a bit like how the bridge tool works.

The polygon ends selected in the pic all have the same number of points & I did end up creating a junction by polygon patching them together & slicing/ dubdividing & shifting the geometry.

http://www.pixelkanvas.co.uk/other/y_junction.jpg

MonroePoteet
04-23-2007, 11:48 AM
I think on a real tile roof, there would be a special cap to join the three ridges rather than a smooth joint. Here's a link to a picture:

http://www.italyhome.com/images/30/BARREL_ON_BARREL_-_ROSSO.jpg

where you can see the cap on the left joining two ridges similar to what you're modeling. Note that it's even a darker color than the roof tiles. So, you might be able to just model a separate piece rather than trying to join them.

mTp

hrgiger
04-23-2007, 01:05 PM
You can extend all the pieces so they intersect each other. Boolean them, and then go back in and fix any ugly polymesses. I've done similar things before. Just try and match up the lines so they are close to each other so it's easy to merge all points together in the end. It will probably require some clean-up so it just depends on how good you want it to look. Me, I'm a perfectionist when it comes to things like that.

Hipcheck
04-23-2007, 04:51 PM
this looks like a perfect chance to use lwcad. drop some splines, then go to the LWCAD tools and chose Profiler. Select the proper profile (or make your own) and then select a point somewhere in the middle of th spline cage. Then bring up the number panel and select the thickness. Good luck and I hope this works for you... it worked great for me when i was doing some spider webbing...

Extent
04-23-2007, 05:35 PM
If you don't have to get too close you could also try splitting each end cap in half, bridge the halves together, then manually create a poly to fill up the triangle in the middle.

jameswillmott
04-23-2007, 05:36 PM
Well it doesnt have to be perfect in this case because the renders will be quite distant (its for a piece of roofing) , but from a construction method point of view, I was wondering if there was a quicker/ better way to handle complex junctions, rather than laborious polygon patching - a bit like how the bridge tool works.

The polygon ends selected in the pic all have the same number of points & I did end up creating a junction by polygon patching them together & slicing/ dubdividing & shifting the geometry.

http://www.pixelkanvas.co.uk/other/y_junction.jpg

I usually just extend the tiles past each other, draw a Y shape in another layer over the join and slice them. Then delete the excess. You might be out by a few millimetres but that won't matter.

hrgiger
04-23-2007, 08:23 PM
this looks like a perfect chance to use lwcad. drop some splines, then go to the LWCAD tools and chose Profiler. Select the proper profile (or make your own) and then select a point somewhere in the middle of th spline cage. Then bring up the number panel and select the thickness. Good luck and I hope this works for you... it worked great for me when i was doing some spider webbing...

Profiler will only work with 2 connected curves as far as connecting them go. Viktor is considering a possible solution that will allow us to do more then that. I'm pretty sure that it won't work in this particular situation but I'm currently playing with it to see what I can come up with.

Hipcheck
04-24-2007, 09:29 AM
Profiler will only work with 2 connected curves as far as connecting them go. Viktor is considering a possible solution that will allow us to do more then that. I'm pretty sure that it won't work in this particular situation but I'm currently playing with it to see what I can come up with.


I must have gotten lucky then becuase I used it on a motorcycle frame which had that exact Y shape config to it (right under the seat pan) and lwcad handled it just fine. Like i said, I also used it for some spider webbing (which has a ton of the Y connections) and again lwcad was up to the task. *shrug* strange...

Surrealist.
04-24-2007, 02:15 PM
I'm with the cap idea. That seems like more of a proper real-world roofing solution.

hrgiger
04-24-2007, 02:21 PM
I must have gotten lucky then becuase I used it on a motorcycle frame which had that exact Y shape config to it (right under the seat pan) and lwcad handled it just fine. Like i said, I also used it for some spider webbing (which has a ton of the Y connections) and again lwcad was up to the task. *shrug* strange...

Do you have a screenshot of that mesh because I would like to see it. I have confirmed that profiler won't join more then two curves at a time. I would be happy if that were untrue.

Also- it won't work in this situation because profiler won't "twist" the geometry to follow the contours of the rooft. You'll get a 90degree angle where the two curves come together totally negating the possibilty of joining the third roof cap.

hrgiger
04-24-2007, 04:50 PM
Here's what I mean about the fusion of the pieces and how they will be oriented. You can see that the two pieces are connected and the third is not. Also, the two that are unconnected, the top piece is facing the correct way but the piece coming down in front is facing not down, and is just following the top piece at a 90 degree angle.

This is the result of using profiler on a three pronged curve.

Hipcheck
04-24-2007, 07:18 PM
hmm... didnt realize that lwcad would twist profiles... in any case here is a screenie and a file for you to check. I'm sure there's a huge difference since mine is tubular and the roof tiles aren't. again tho... i had no idea that lwcad would twist... learnt sumthin new!

hrgiger
04-24-2007, 07:32 PM
Are those actually merged? Or are they just intersecting. I guess I was hoping you would post a closeup of the intersections, a wireframe view to see how they merged. Because LWCAD's profiler will as many curves as you have, it just won't join more then 2 at the intersections.

Well, LWCAD won't twist the profiles, and that's the problem in this situation. Although, you can scale either end of the profile which is nice.

hrgiger
04-24-2007, 08:33 PM
Ah, nevermind. I see you posted the object, thank you. Yeah, as I thought, LWCAD didn't actually merge any of this geometry together, just intersected it. Yes, you are right, in your case, it makes a big difference that your geometry is tubular because it hides the fact that the mesh isn't actually merged at the joints (and also makes the orientation of the profile unimportant). In the case of the half pipe roof caps though, the unmerged geometry is painfully obvious.

Hipcheck
04-24-2007, 08:41 PM
Ha! after closer inspection you are indeed correct. they are not merged as i had thought! (although I did have to zoom a good distance in... how deceiving!)

I bow to your superior knowledge! Thanks for setting me straight.

hrgiger
04-24-2007, 09:40 PM
Well actually, I should thank you for bringing something to my attention. I didn't realize the twist (angle) feature in the profiler panel before. I thought it was limited because I thought when you twisted, it had to twist the whole profile at once even on more then one curve, but it turns out that you can twist each curve end independantly and still have it connected (only on two curves at a time though). It still doesn't solve this particular problem with the roof caps since there would be 3 curves connecting at one point but it's very good to know.
In the case of this geometry, I'm now leaning towards not merging them and making an overlap or a slightly visible joint.

WaxSteel
04-25-2007, 02:31 AM
I recalled seeing a good example on tubular modeling a bmx bike with some screenshots here. Maybe its not that appropriate to this discussion.
http://www.spinquad.com/forums/showthread.php?t=4843&page=2&highlight=bicycle

Hmmm, the poster has taken down their pics - the description on page 2 might be interesting though.

prospector
04-25-2007, 03:24 AM
perchance like this?
Just slice the depth you need and delete XTra.

prospector
04-25-2007, 03:48 AM
OOps..my bad
you needed them in halves and bent..sorry
Well,first pic shows how they were made with just box and extruded

WaxSteel
04-25-2007, 04:23 AM
Very Nice! - since its a cap it can be made differently to the other geometry in the roof ridge - it doesnt have to be welded exactly to points.

Guess it shows you need to model in very basic form & use subpatches for anything like complex/smooth junctions.