Architectural Desktop Roofs

After struggling with several clients' questions about rather "normal" roof conditions and how to build them in Architectural Desktop^TM, I set out in attempt to "master" this topic.

My first trick is simply to avoid attempting to build the roof right off of the plan; though it often works fine to snap along ADT walls or simply convert Wall objects, I find that I often make mistakes this way or simply get a different result than what I wanted.

I use Closed Polylines to define the shape of my roof, in plan, and then Convert the polygon into a Roof object. Take the figure to the left, for example, first of all you can't make a round roof in ADT, you need a Polyline that approximates a circle. Since you are allowed to create a Polygon with up to 1024 sides, approximating a circle should not be a problem. The roof I have illustrated to the above/right only has 20 sides because I found that working with numbers as high as 75 makes Grip editing cumbersome.

To create the Dormer, I simply combined the 20 edged Polygon with 3 sides of a rectangle using the Pedit command to join my design together into one Closed Polygon. Then, I used the "Convert to Roof" option in ADT's Roof menu and set the Slope. To make life easier, you may want to remove all overhangs before attempting to adjust the strange roof form you will get at the point where I show a dormer. This part will not happen automatically. But, you can use Grips to take the Hip Roof you will get and turn it into a Gable - as shown. To set the Gable Dormer up higher on the Cone, I simply edited the Dormer's two side Edges and set their values to the height I wanted my Dormer above the Cone's Fascia.

To make this clearer, let's break the concept down on a simple example:
Cones, Dormers and Gables

We'll take a simple Polygon shape as shown to the right and use ADT's Convert to Roof routine to create the basic model and then make modifications to that form.
Viewed from an Isometric Vantage Point, the default roof should look something like the figure to the left: 2'-0" O.H. and a 6" and 12" pitch. To make the modifications described next, it is best to view the roof from a similar vantage point. I usually type "VP" on the command line and pick an altitude near 50 degrees and a plan angle somewhere near 230 degrees.
If you select your roof with Grips, you can easily transform any of the Hipped Roofs into Gable End Roofs by Stretching the Ridge Grip along a direct path (X or Y-axis)- Use Ortho to make sure you Stretch straight.
Use Edit Roof Edges/Faces...to move the Dormer to a higher point along the Main roof. You can either select the Fascias or the internal Wall edge lines to get the two edges to move up.
The illustration to the right shows the Edit Roof Edges dialogue box and what I modified to raise the Dormer: (A) Height for Edge 0 and Edge 1.
Illustrated to the right is the final result of these changes. By using these techniques and expanding upon them you should be able to create quite a variety of Roofs.
Here's an example of 4 Gables meeting at a single point over a square plan. In order to trick ADT into allowing me to create this roof, I had to make a Cross shaped Polygon - similar to the plan used above but perfectly square. After I let ADT build a roof on a Cross shaped Polygon, I Stretched the Hipped Roofs out to create Gables and then Stretched the Fascias back to a point forming a nearly perfect intersection. If you attempt to stretch the edges (or Fascias) back to a perfect point of intersection the roof routine will create another form so you will need a slight amount of error at the corners.
Doubleslope Flat top Roofs
Roofs with flat tops were also tricky for me to figure out. This problem actually came out of a need to create a cone shaped roof with a hole or oculus in the middle; as illustrated in the image to the right. Though I have not been able to actually create a roof with a hole inside, I have been able to create sloped roofs with flat tops.
This image, right, shows two basic roof shapes with flat tops. They were both created by converting polygons into basic roof shapes and then, by using the Modify Roof Dialogue box, they were converted into the shapes shown.
1.The simple trick is to make the roof shapes "DoubleSlope" via the Shape drop-down list. 2.Then specify an "Upper Height" relative to the "Plate Height" where the Flat part is to occur. 3.The last part is to specify zero (0) for the Rise and thus zero (0) for the Slope.