What's New – Specify basins and protrusions by drawing their outer boundary

Mar 12, 2024

SCALGO Live has long supported creating basins and protrusions having side slopes with a given gradient.   The way this works is that you draw a polygon covering the bottom of your basin or the top of your protrusion (hill).  Then you specify a gradient, and SCALGO Live automatically interpolates between the drawn flat area and the surrounding terrain while respecting the specified gradient.

A basin created by drawing the bottom area and adding slopes on the outside.

There are use cases, however, where it is more natural to be able to specify the outer boundary of your basin or hill.   For example, you may have a given plot of land where you want to create water storage.

SCALGO Live now supports this use case:    Again you draw a polygon and specify a gradient, but this time SCALGO Live adds the slope on the inside.

A basin created by drawing the outer boundary and adding slopes on the inside.

The tools you have always used for creating basins and protrusions now support both ways of specifying side slopes.  Use the checkbox "Side slopes are outside" if you want to add slopes on the outside of your area (the default is now to add them on the inside).

The new controls for specifying if side slopes go on the inside or on the outside of the drawn area.

The two modes behave a bit differently:

  • When adding outside slopes, the polygon you draw is a flat horizontal polygon (since it's the bottom of your basin), so in the profile view you will see all vertices at the same elevation (and you cannot change this).   How far the side slopes will go depends on the elevation of the terrain, for an uneven terrain it is not easily predictable.
  • When adding inside slopes, the polygon you draw actually has 3D coordinates (SCALGO Live automatically samples the terrain at each vertex).   This makes it possible to create a basin whose outside aligns with the terrain along the given area boundary.   From these 3D coordinates, SCALGO Live then computes the appropriate sloping to achieve the target depth (or height for protrusions).    The depth is always measured from the lowest boundary vertex, the height is measured from the highest boundary vertex.

    When you edit the boundary of such a basin, you may have to readjust the elevations at the vertices to make sure it again aligns with the terrain, otherwise you'll have sharp edges on the boundary.