Site model - modifiers spilling into each other

[line-weight]

I've got a site model set up with a recessed pad, with retaining wall, into which a building sits:

 

 

Just uphill of this I want a flat pad, at a higher elevation. So I use the standard 'pad' modifier:

 

 

Which gives me the pad I want, but I don't want it to spill into the hole I've created with the other modifier. Is there some way I can stop it doing that?

 

Tried using a 'grade limits' modifier but that just created this:

 

 

I think it's applying the grade limits to both of the modifiers but that's not what I want.

[AlanW]

Hi, Post a file? Check that noe of the DTM modifiers overlap, or touch, keep them a few mm apart.

[line-weight]

Yes, they were touching, and moving them slightly apart has fixed it. Thanks.

[P Retondo]

This is a common problem, and the more complex the site modifications the worse it gets.  Although Alan's solution is spot on from a pragmatic point of view, the situation is not always this simple.  It seems to me that the site model is long overdue for an upgrade.  Layers of successive modifications should be handled by the software like subtractive instructions to a milling machine.  Simpler, faster, more intuitive.

[AlanW]

It would be a good improvement if modifiers could touch and produce the desired results. Overlapping should still be a no no. This would simply things and make modifying the site easier.

[line-weight]

I'd also like a modifier that simply raised or lowered an area of ground relative to and parallel to the 'existing' surface, something that doesn't seem easily achievable at present.

[P Retondo]

For me, having the site modifiers behave exactly the way solid addition and subtraction work would be the simplest and most powerful implementation.  Boundary overlap would not be an issue.