Courtyard roof - Joining roof sections at a 90 degree angle

How do you join roof sections that are at a 90 degree angle to each other? This relates to making a roof for a building with an open courtyard. Each side of the open courtyard has an angled roof which is easy enough to do. The problem is joining the four roof sections so that they join with a 45 degree angled seam, like in RL. Any suggestions?

Hi, NikNak -- Yes, in the Texture window of Edit, choose planar mapping instead of default. You'll find it much easier to get those angled sections to line up.

Thanks Rolig. Will give it a try.

Ahh..... I wrote my note before I had my morning coffee and was interpreting your question as a texturing one. As I read it again, it sounds like the question is actually about the prims themselves and how to get the edges angled right to match up... Sorry about that...

So, try making each corner of your roof from a hollowed four-sided pyramid that has two of the sides cut away. Start with a cube, taper X and Y 100% so the top comes to a point, hollow it, and use path cut to carve away the sides you don't want. Or .... do the same thing but start with a diamond instead (twist both X and Y by 45 so that the axes of the object come out its edges instead of its sides).

THEN texture the sides by using planar mapping so that the texture is parallel to the base of the pyramidal remnant.

Easy way to make versatile roof panels.

Start with a cube. Reduce the Y dimension to the desired thickness of the roof panel. Set the X dimension to the desired length of the panel (axis parallel to the eaves of the house). Set the Z dimension to the top to bottom length of the panel. Use X taper and X skew to shape the panels, and use planar texturing. Rotate the panel on the X axis to the desired roof pitch.

When making panels that meet at an angle, start rectangular and intersecting. Now adjust the taper and skew so they match on the edges.

You can make almost any roof shape this way.

Take a look at the roof of Winants Hall in the Rutgers University "RUCE 2" sim, for an example of how this method can be put into practice. It's the building in the SW corner of the sim, with a complex roof that has lots of gables and dormers. And none of those roof panels have any unusable projections on the inside.

Hi Rolig, yes it was a prim issue however your texture oriented answer gave me a few ideas, so it was useful. I'll try your pyramid idea. I did something similar before but had unused projections in my roof.

Ceera, I'll take a look at the RUCE 2 sim and your technique. I have these unused projections on the inside on my roof that I'd like to get rid of!

Thanks so much ... NikNak

I have admired that building before, Ceera, and have gone back more than once to see how you made it. Very nice work.

You seem to have used the cut/hollowed pyramid approach on the four corners of the roof, but used the taper/skew approach elsewhere. Adjusting the taper and skew to match on all those angles must have been a real bear, since adjusting either parameter changes the angle on both ends of a roof panel. You seem to have done it, though, and without having to cheat by burying the excess of one panel in its neighbor. You either have a lot more patience than I do or there's a trick I'm missing. What's the secret?

Hi Rolig.

On the corners I did use the pyramid approach, since those could just as easily be solid. The area under them didn't need to be usable, so why waste additional prims?

The rest is done as I described in my earlier post.

What I usually do is align the two panels so they intersect and overlap, with the longest edges touching corners. I take a quick look at how much of the other edge is exposed under the roof. Then I adjust taper to reduce that length to about half that distance between the corner and the other roof panel. Adjusting skew to half the taper value squares the far edge and snugs the panel against the other panel. Then fine tune both the taper and skew to get a good fit.

I sometimes use an alignment grid texture on a roof to get the textures to flow smoothly from one prim to the next. But as much as anything it's a lot of careful by-eye tweaking of offsets.

Another trick: Rotating an angled panel can be a real pain, especially to anything other than 90 degree increments. So link it to a non-rotated root prim, and then rotate the assembly "by the numbers". The rotation will be applied to the root, pivoting the angled panel on that root prim's center. Really handy for things like turret roofs, where you want 6 or 8 panels to meet in a "conical" roof.

FYI, in that same sim, the roofs of "Old Queens" (the one with the white bell tower) and the Kirkpatrick Chapel (The church toward the NE corner) also have roofs using this technique. Look inside the attic of Old Queens for some fascinating detail levels. *grins* On the other hand, Geology Hall just uses interpenetrating forms for the dormers, as it didn't need a functional attic.

here you go dude...


when you taper it changes both edge angles but here is the trick...

set the skew to 1/2 that of the taper (+or- for direction) to bring one side back to a 90 degree angle.


so if you set your taper for .45 make the skew .225 - you can use other ratios to get different angles but its all very predictable.

hope that helps

Yeah... I got that much just in fooling around, von, and I've done Ceera's trick before in my own clunky way. There's still a lot of iterative back-and-forth to getting the edges to line up properly, though. I'm not as patient as I would like, but I can get obsessive about getting things right (a nasty combination), so I was hoping there was a clean alternative to all the fiddly work. It looks like the answer is just to work harder on my patience.

Ceera: Those really are lovely buildings. I've poked around inside several of them at odd times and have always come away feeling humbled. Thanks for the encouraging tips.

Okay, I know I'm a beginner, but I'm working on a house with two wings and dormer, and the way I got the roofs to work was by making triangular pieces for the spots where they join.

If the sides of the roof are lying in the right way, you can copy them by shift-clicking on the Y arrow, and then path-cut away the half that's not needed.

If you were laying down sheets of plywood in RL, that's what you do.

I wanted the attic effect underneath, and it works both outside and inside.

That works, of course, but it still begs the question of how to get the angles to match up well, which was what the OP asked and Ceera addressed. When you have rooflines that intersect, as where you have a dormer, for example, it's not necessarily easy to figure the proper angles on adjacent pieces. It's especially challenging if you want a finished attic look inside, so you can't have extra prim bits sticking out. As a final issue, it's usually important to build with the fewest prims possible. That means looking for ways to make trapezoids that match well instead of plugging holes with a mess of triangles.

All in all, Ceera's method is the best I've seen for addressing each of these matters, even though it still involves some manual fiddly work.