merge two boxes

hi everyone,
i have a simple question.

i have an obstacle in a channel whose geometry is composed by the union of a collection of simpler domains of type box2D.

my aim is to create a single domain on which implement the bounce back dynamic. Create a unique object is necessary to calculate the drag force that act on it.

so, how can i implement the command “merge”?

the user’s guide says: <<If the domain is the intersection or any other geometric operation of simpler domains, you’ll need to play with boolean operators inside the definition of your domain-functional.>> but i don’t know how to implement it…

since the “load geometry” oddly doesn’t work, and the dotList method seems to be quite raw solution for this purpose, i thought about this way to solve the issue.

any suggestion would be greatly appreciated.