Remove inside geometry of a model - geometry

Question

For a project I'm currently working on I'm looking for a quick and easy way to get rid of inside geometry of a house model.
This house model has everything in it, floors, inner walls, stairs, kitchen, you name it, but I want to remove all geometry on the inside so I'm basically left with just the "shell" of the house. say if you would "submerge" the house underwater, everything touched by the water I want to keep, the rest I want to be removed (maybe a weird explanation but I hope it's rather clear what I mean).
Because I need to do this process on a lot of different house types, it's simply too much work to do this manually by hand, and I'm therefore looking for a method which can do this quickly.
I use 3ds Max for my modeling, but solutions in different software, for instance Meshlab, are fine too!
Thanks in advance,
Maik Bentlage, iBuild

Answer 1

For a MeshLab solution, this blog entry describes a method to use ambient occlusion to remove interior vertices. In MeshLab 2016.12:
Filters > Color Creation and Processing > Ambient Occlusion
Filters > Selection > Select by Vertex Quality. Play with sliders to select low quality values, i.e. all the interior vertices that are not visible (try min 0, max 0.1).
Filters > Selection > Delete Selected Vertices
This isn't a perfect solution, but may be good enough for your needs. If you can determine a max quality value that works consistently for your models, you could easily script this for batch processing.

Answer 2

It really depends upon how each house was created.
If it’s a hierarchical approach, i.e., the house is a parent and models inside (kitchen, floors…) are children, then you can easily use a simple MaxScript such as this one to delete all children from your scene (inspired by this thread from cgsociety) :
global meshes_list=#()
fn selecting_children ancestors =
(
for i in ancestors do
(
counting = i.children
if counting.count>0 then
(
for x in counting do
(
append meshes_list x
)
)
)
return meshes_list
)
rollout hierarchy_rollout "Hierarchy Operations"
(
checkbox Checkbox_DeleteSelection "Delete Selection" checked:false
button select_children "Select All Children"
on select_children pressed do
(
select objects
sel = selection as array
x = selecting_children sel
select x
if Checkbox_DeleteSelection.state == true do
( delete selection )
)
)
createDialog hierarchy_rollout 200 150
Just make sure that you don’t end up deleting other meshes or houses as well!
If they are not hierarchically ordered, then you can Select by Name (press H) and delete everything manually, but more quickly than selecting them one by one with your mouse.
If the whole house is a single mesh (including props inside), then I am not aware of any existing way to automatically delete everything inside. You can still select by Element (after converting it to an Editable Poly/Mesh) and, after selecting the house (assuming it's a single mesh), pressing Ctrl + I for inverting selection and delete everything. But it’ll still be time consuming.
A workaround might be to attach every house into one gigantic mesh (just open the attach list to select everything at once) and to use the rectangular selection to select only the highest part (which should isolate props or most of them) of everything, in the Left or Right Wireframe Viewport, and then press Ctrl + I.