How can I make some Landscape sculpting modifications?

There are 2 things I would like to add to the sculpting and landscape creation mechanics and could need some help on where the code is that I need to modify.

  • I would like to set the starting “flat” value of the landscape when created. For example, the heightmap height goes from 0 - 100, and when creating it, it starts flat and unaltered at the height of 50, in the middle. I would like to have a dynamic creation height that can be defined during the creation of the landscape. So first, where is the code for adding a new parameter field to the editor interface of the landscape creation, and where is the section of the landscape creation process to input this parameter?

  • Second, there is a unadded necessity while sculpting the landscape, when two landscapes are on different heights, and you would sculpt over the boundary onto the second landscape, the height at which is painted is relative to the landscape, so if one is higher than the other, a height difference is visible leaving a gap. So where in the code would I modify the sculpting algorithm to incorporate the levels z value?

Thanks for any help on this.