Hi Tony,

> how you can create a tiled roof using a single surface without
> creating individual objects

Well, you can use Boolean Union on your 2 objects in your example file to intersect them and remove the common interior area and then they will be combined into one single object.

But since you've got sharp edges and 90 degree corners in different pieces of your shape, you won't be able to make it out of literally just 1 single surface because just one single surface has to be smooth throughout its interior region. If you have a form that has sharp creases in it, that will be made up of multiple faces that are separated by the sharp crease.

For something that has distinct elements like that, it's easiest to create replicated separate objects for it.

If you want to make some kind of big surface with a repeated lumpy pattern in it, you could look at ZSurf for generating a surface from a texture image:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3825.2

But you're not going to get something with that kind of distinct sharp edges in it with that method, if you want it to actually look like distinct tiles then creating individual objects is the easiest and of course it also maps to the actual physical model as well.

- Michael