Modeling a four sided roof

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Modeling a four sided roof // Tech Forum

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Post by Tiles // Mar 14, 2009, 12:55am

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I have a problem and am stuck.

Let's say you model a house. Modeling a normal twosided roof is relative simple. You sweep the roof, then sweep the lower part that overcomes. What's left to fix is the gable. I usually cut away a part of the building, then mirror model it, and voila. Makes the building an idea smaller, but the gable is sharp and fitting now.

Now let's say you have a roof with four sides. The four sides refuses to fit together. They have another angle. Means the parts at the front and the back goes with the same sweep amount a bit more downwards than the two roofparts beside. Doesn't fit. Plus i would need to use the Modeler to reconnect the overcoming roofparts because Workspace modeling tools are in trouble with such geometry. And i would miss a way to do that in a correct manner anyways. Sweep goes out straight ...

As told, i am stuck at this problem. Looks so easy, makes so much trouble. Because i want the overcoming roofparts to be equal thick at any points. What's a good way to model such a four sided roof that overcomes at the sides?

Post by Jack Edwards // Mar 14, 2009, 12:58am

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Delete the two interior faces at the corner then weld the bottom two verts, followed by the top two verts. You can use that technique all the way along your roof seam as well.

BTW, you can extrude a selection of faces as a single group. There's no need to extrude each face separately.

Post by SteveBe // Mar 14, 2009, 1:27am

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One approach.....

Post by Tiles // Mar 14, 2009, 1:31am

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Delete the two interior faces at the corner then weld the bottom two verts, followed by the top two verts. You can use that technique all the way along your roof seam as well.


Thanks for the suggestion Jack, but the result doesn't really convince me. By welding the vertices they change their position, means the angles becomes wrong. And in fact the roof seam bends down by that. This is really an interesting problem. As told, looks so easy ... :p


I have attached the problemfile in case you want to try too :)


BTW, you can extrude a selection of faces as a single group. There's no need to extrude each face separately.


I know, but the result always goes in odd directions. Especially when the initial angles are different like in my case here :)

Post by Tiles // Mar 14, 2009, 1:39am

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Thanks SteveBe. Interesting approach. But how do i get the overlaying rofparts equal thick now?

Post by SteveBe // Mar 14, 2009, 1:50am

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Most roofs are flat at the bottom of the eaves but...

Post by Jack Edwards // Mar 14, 2009, 2:23am

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Inference snapping tools would help here, and would allow you to position the verts to create parallel lines. Though unless the house needs to be architecturally accurate, why worry to get the angles perfect?

My advice is to eyeball it and if you need the faces to lay in the same plane, you can select both faces, set tangent coordinate mode and scale them down so that they are flat. I doubt a real house of that size would have perfect angles anyway... lol. ;)

Post by Tiles // Mar 14, 2009, 2:46am

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Though unless the house needs to be architecturally accurate, why worry to get the angles perfect?


Me little devil called perfectionist calls me to :D


I think there is simply no way to achieve what i want to achieve. But you are right Jack. There is really no need to anyways. Seems that i was trapped by a fixed idea here. Shown ways will do the trick and will be good enough :)


Thanks for the help guys :)

Post by Jack Edwards // Mar 14, 2009, 3:01am

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LOL, glad we could help! :D

(BTW, if you do want it to be perfect you could do the math on graph paper, then type in the coordinates for the vertices... ;) ...:p)

Post by jamesmc // Mar 14, 2009, 4:48am

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Total Posts: 2566
Interesting challenge.

Found what that style of roof is called. It's called a mansard roof.

Can be seen here and may give some clues how to build it.

http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/e/e9/Mansard_(PSF).png&imgrefurl=http://commons.wikimedia.org/wiki/File:Mansard_(PSF).png&usg=__OwktdQh9D41M7BN2UVLQCHqXoW0=&h=1341&w=2130&sz=387&hl=en&start=10&tbnid=5uH9hyMpn_OmvM:&tbnh=94&tbnw=150&prev=/images%3Fq%3Dmansard%26gbv%3D2%26hl%3Den%26safe%3D active%26sa%3DG

Post by Tiles // Mar 14, 2009, 4:53am

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Yes, a really interesting problem :)



(BTW, if you do want it to be perfect you could do the math on graph paper, then type in the coordinates for the vertices... ...)


(YIKES! I fear my math skills are too weak for that. One, two, many, one and many, two and many, lots, one and ... )

Post by Emma // Mar 14, 2009, 5:20am

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Just another suggestion, first model the basic house like this

18923


Now it's importatn to switch to Tangent modus

- first mark the two oposite edges of X coordinates and then use the corresponding to X block to enlarge

- now do the same with the Y edges

18924

This way the roof will just enlarge horizontal

- now simply move the edges downward


if you add one more loop you can do the same also with faces

18925

Post by RAYMAN // Mar 14, 2009, 5:48am

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You start with the wrong end first....

First make the roof then make the walls....

But I post a lot about Sketchup all over the place here.

A small little tip.....thats a good point to find out a way to make things

even in TS.... try it out in Ketchup first.. its easier and you can

use tools that draw in parallel.....;)

Post by Tiles // Mar 14, 2009, 6:04am

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Emma, your way is nice too. But shows the same problem than the other solutions: no equal thick roofparts. And that was my initial problem :)

Hmm. First the roof. That would indeed be a possible solution. That way you can give the roof the same thickness everywhere. Only problem that way would be the bool operation with the rest of the building. Nothing unsolvable though ... . Thanks :)

Post by RAYMAN // Mar 14, 2009, 6:20am

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Emma, your way is nice too. But shows the same problem than the other solutions: no equal thick roofparts. And that was my initial problem :)


Hmm. First the roof. That would indeed be a possible solution. That way you can give the roof the same thickness everywhere. Only problem that way would be the bool operation with the rest of the building. Nothing unsolvable though ... . Thanks :) No bool operation ! just a simple xtrude !;)

Dont hesitate to use the free version of what I said below your going to learn a lot about how to construct things in Truespace (free!)

Post by jamesmc // Mar 14, 2009, 6:27am

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Total Posts: 2566
My attempt at the four cornered roof. :D

I just kept with edges, resized, dynamic sweeping when needed a couple of times.

Like someone else mentioned, worked from the bottom up.

Post by RAYMAN // Mar 14, 2009, 6:41am

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Heres the roof up to the point when you would ad the walls.... so no need for booleans... Note that you can position and triangulate th inner side of the roof wherever you want it to be...all without booleans

some of the vertices were used for construction and erased

Post by Tiles // Mar 14, 2009, 7:12am

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I see. Thanks :)

Post by jazzer1960 // Mar 14, 2009, 7:24am

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If this is the type of roof you are after then use the bevel tool.

On the selected top face on a cube use bevel and left click to get different angles.

Post by Tiles // Mar 14, 2009, 8:42am

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Hmm. It seems that the initial problem got lost, heh :D


It's no problem to sweep/bevel/ model something that looks somehow like it could be correct. That's what i did now, but that was not the initial problem :)


I initially wanted my roof to have equal thick roofparts where they overhang, not the straight end as shown here now more than once. I would even prefer to have 90 degrees angles at the end of the roof instead the also straight end here. Bevel will simply not work in that case.


Nevertheless thanks for the suggestion :)

Post by RAYMAN // Mar 14, 2009, 9:57am

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tiles the way I showed it to you does exactly that make the roof same thickness everywhere. In the post here I show you where Ketchup can do more.... even if you move walls that are underneath the roof the cuts

of the walls go with it ... the roofthickness is always the same....;)

Post by Changa // Mar 14, 2009, 11:42am

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The way I have made roofs in Ts before I moved to SketchUp and Kerky. It is very similar to Rayman's approach. Done in 3 simple steps. Overhangs ends of the roofs are usually vertical now days. If you want to have them 90 degrees and all the roof of the same thickness, just do the same on the bottom part of the roof and then move the bottom outer edges horisontally inside. Hope it make sense.

Post by Tiles // Mar 14, 2009, 10:58pm

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Thanks Guys :)

Post by Cammer // Mar 16, 2009, 7:00pm

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Here is my attempt at the 4 sided roof. I used 4 cubes for roof,
united these, then 4 subtract cubes to trim the excess off the tops
and 4 subtract cubes to trim the facia side around
the bottom edges.
18990

Post by fahembree // Mar 16, 2009, 7:45pm

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Here is another option, but I admit that the 90degree edge fascia is approximated. First draw a cube and scale to the approximate desired size. The select both the top and bottom faces (both faces selected), an then use the bevel tool to bevel both faces at same time. The exit bevel tool and select the small faces at center of both the top and bottom and lift both faces up to the desire roof peak height. Then select the lower edges of the roof fascia and scale to approximate the 90 degree edge. I sure that if you use a front view (zoomed in close to the sede),when scaling you can get get a angle that is very close to 90degrees

:)

Post by manxie // Mar 17, 2009, 4:18am

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Hi Guys, This roof was a lot easier, no pointy bits.:D

Post by Nez // Mar 17, 2009, 5:33am

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haha - but it will probably leak... in the UK we just don't seem to be able to build flat roofs properly...:D


I have to admit, to create this interesting eaves detail, I think I'd start with with a series of shallow cubes, slope them to create the necessary pitched sides of the roof and then boolean subtract away the parts I didn't need, but that's only because I use booleans for almost everything... but some other good methods here which work pretty well too...
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