Procedural City: Building Roofs

This is a shorter post that was originally split off the longer "procedural city update" post I was working on. Let's get back to the house roofs. I want to work on building interiors, but the roofs aren't quite right and don't have enough variety. They're intended to be simple to generate and fast to draw. Most small house types had simple sloped roof sections on each part of the building. Since 3DWorld can currently only generate rectangular, L-shaped, and T-shaped houses, there are either one or two rectangular parts to the house.The roof needs to look correct and interesting for all of these cases.

Here is a list with descriptions of some of the common house roof types. Flat roofs aren't too interesting, so I won't discuss them here. I'll leave them for larger buildings. I was originally adding only gabled roofs to small 1-2 part houses. I recently added hipped and half-hipped roofs into the mix (randomly selected). It was easy to add these roof types to simple rectangular houses, but adding them to multi-part houses proved to be more difficult than I expected. The two different parts of the houses can be different widths and different heights, which makes the math for lining up the roof triangles and quads complex. It took many iterations to get a hipped roof to line up with another roof section that had a different width and peak height. There are quite a few special cases where sections of roof need to be clipped or extended so that they join properly with no holes or triangles that stick out. In addition, I need to make sure the roof from one part doesn't intersect the living area of the other part. This wasn't a problem until I started adding building interiors, in which case it's obvious if the roof extends into, say, a bedroom.

Here are some examples of two part houses and what their roofs look like. There are maybe a dozen different pairs of roof types/intersections. Most of them look correct, but a few of them still look odd. For example, some parts have a roof on each side that end at a horizontal line that would need a gutter between the sections as in the first screenshot. I'm not sure if I'll go back and fix them or not.

Low house with relatively flat hipped and gabled roof sections.

L-shaped house with hipped and half hipped roof. The roof line consists of complex geometry and angles that were difficult to get right.

House with two gabled roof sections intersecting at a T-junction.

Large house with low hipped roof on taller section and gabled roof on shorter section.

L-Shaped house with gabled roof intersecting at a T-junction and a smaller, lower porch roof in the back.

There are plenty of other house roof styles out there. I'm considering adding more of them, but it will probably have to wait until I've made more progress with building interiors.

I might have to go back and improve the variety of office building roof types later as well. Right now there are only two types: flat and beveled edges. This image shows two buildings with flat tops and beveled edges.

Office buildings with roofs that have flat tops and beveled edges.

On a somewhat related note, I added glowing colored lights to those antennas on the tops of tall buildings that appear at night. I think these are supposed to keep planes and helicopters from crashing into them. I wonder if that means I need to add helicopters in the sky above the cities as well?

Night time city showing colored lights on the tall building antennas.