Allow new topography sub-divisions to recess into topography

[mhiserZFHXS]

The new topography system looks like it is probably 10 steps forward and 2 steps backward. Overall, it looks like it improves on a lot of issues and is a better foundation for improvements moving forward, but it does have some problems.

One issue is that the new sub-divisions cannot recess into the topography. They can expand upward, which is wonderful, but we also need them to go down so we can better model things like roads and parking lots. We are still going to have to rely on splitting the topography to do this, which can cause tons of headaches, as we know from the previous system.

[taaviSWPX2]

Having the ability to set subdivision height as negative is critically needed for making roads and paths. Being able to excavate with floors and roofs doesn't provide the same functionality.

[wr.marshall]

@kimberly_fuhrman-jones see the following is on the roadmap: :mountain:️ Excavate a toposolid with a floor, roof, or another toposolid :light_bulb: - Architectur...

If there is another idea similar which has been accepted please combine with that idea

[ksmithBMBHQ]

I've seen it suggested that sub-divisions should be allowed to have negative height. This makes little sense, and still isn't particularly flexible.

Instead, we should be allowed to offset the location of a subdivision from the surface of its toposolid. This could be in a positive or negative direction. This only works as a separate parameter from sub-divide height. A sub-division with a 6" height could be offset by -6", making its top surface flush with where the toposolid top surface would otherwise be. But also, you could offset it by -1', which would drop its top surface a further 6" below the toposolid surface. This could work very similarly to the excavate feature in 2025, however it would also have the benefit of dynamically adjusting the excavation to the topography defined by the toposolid since the sub-division creating the excavation is directly hosted by the toposolid. 

Imagine combining this with subdivision types that have a multi-layered structure (similar to this suggestion). You could then fully model lots of landscape details.

[richard]

Also come across an issue, when you split the topo to make a sub division. when you go back into edit that split, by adding new line it affects all of the levels of the split sub division,  i have a online support meeting with Autodesk and no solution was agreed apart from to draw it as a subdivision first and when the design has been signed off then use the split tool.