For the conceptual and 3D creation the shell tool is probably the best tool IMHO since you can draw the planes visually in 3D very quickly.
Easy to draw triangular surfaces (see next paragraph). BUT for the documentation phase I have to agree with Barry about using sloped
walls since shells will not clean up nicely with each other like walls do.
For fun though, here is how I would use the shell tool to make this conceptual model: In the image below I used a slab at zero and an elevated
slab as reference planes then I drew rectangular shells. No rotate or trim necessary. Next, using the move node option in the pet palette I
made each surface triangular by dragging one node on top of another on one of the sides. Of course without more than one view I am sure
I did a bang up job of replicating the model exactly as you have it.
To model it correctly you need the x,y,z points of each vertex. And for this to work well with the shell tool you would want to create the horizontal
planes that represent what would be the structure's roof and floor slabs. You would use the roof tool (single plane)* in the case the planes are
inclined or slab tool if they are not inclined. From these planes you can draw the shell contours in 3D.
Onto the doors and windows, you would have to use a skylight object in the case of a shell if you wanted to have an object that is actually hosted
and cuts through the shell. Or you could cut a hole in the shell where the doors and windows should go and either use the Curtain Wall tool (recommended)
OR place a wall that is as wide and tall as the door/window and place a standard door/window there.
*Side Note: The roof tool (single plane) is a good choice to use as a design tool for odd planes in 3D views as well since you define your roof plane
by defining 3 points in space.
http://www.graphisoft.com/ftp/publishing/ac15_help_INT/Files/wwhelp/wwhimpl/js/html/wwhelp.htm#href=...
So if you know what the coordinates are you can input them into the Tracker. A trick I use is to place columns (any object would work really)
to mark the points graphically so I can snap the roof plane to points in 3D. I first place a small circular column in floor plan and then stretch its height
in 3D to the appropriate z-height. I then have "tent poles" to references to draw a roof plane in 3D.
Best regards,