As all who use 3D Printers know you cannot lay down plastic in the air, it must build from the base up. Some slicing software creates a base to build on but apart from using a water soluble base the results are far from ideal. Perhaps the programmers of Rhino could consider the following as a useful addition.
The user takes a block of suitable size that takes in the part of the model that is above the platform. The model is then Boolean’d leaving a mould of the section that needs support. All this can be done now but one further step is required. There needs to be a function that allows the user to create a suitable surface on that mould that will allow easy separation and a good quality print. Perhaps the selectable texture could be a cross hatch pattern, conical spikes or a myriad of other possibilities.
Hello - please post a simple example (3dm file) of what you are asking about.
-Pascal
Please find attached file as requested.
McNEEL_EXAMPLE.3dm (1.74 MB)
You’re kind of describing what any decent slicer software already does… check out Simplify3D or Cura…
I think is not good to make support structures inside rhino unless is a specific scenario with complex shapes or angles, otherwise is better to make them in the slicer software as @cairn mentions, because, among other things, it allows you to set different values of extrusion and speed to reduce the amount of time and material while printing supports. if it comes from rhino, the slicer will take everything like a printable body.
For those specific scenarios you can use the draft angle analisys to check where support is needed, lets say setting values like -45 in blue -50 in red, then you can manipulate and orient your object to reduce red areas.
Also I think you can use the _TestSilhouette command to make some curves at those angles and have an input to extrude the supports.
Thanks for the info, it would appear that I am using a very basic slicer.
Cura’s free and pretty deep, although I forked out for Simplify 3D mostly for the speed.
I do this quite a lot, as you can save a lot of time/material by making ‘tree-like’ supports. Sometimes I root the ‘tree’ on the part itself…
Meshmixer has a tree-like support generator… I need to look into that a bit more.
Here’s a table base automatically modelled using Meshmixer support… 
