Select primitives on the outside of the mesh

   3726   5   3
User Avatar
Member
3 posts
Joined: July 2019
Offline
Hi, i have multiple models of rock formation, each consists of multiple individual stones, that are stacked together and i need to remove inside faces, so only the visible geometry will remain

I tried:
-manual marquee select visible from multiple different views in scene view, time consuming, and impractical
-sop_remove_faces however, it is not 100% accurate and I end up with either holes in mesh or unnecessary geometry inside, plus i don't want to check each model manually
-create group using Bounding volume using isooffset and vdb from Polygons but this method has same issues as sop_remove_faces
-create group using Bounding object, this does not take account individual intersections between stones
-boolean, so far the safest option, but still, if there is space between the stones, some inside geometry remains
-baking AO, selecting and deleting the darkest areas, also not very reliable

Another idea i had was to use intersect VEX function, however do not know VEX that well yet.
User Avatar
Member
335 posts
Joined: April 2018
Online
jo_han
-boolean, so far the safest option, but still, if there is space between the stones, some inside geometry remains

Can you clarify this? Boolean Union should remove all the internal faces.
User Avatar
Member
3 posts
Joined: July 2019
Offline
This happens if there is any space between the stones

image just for illustration:
Edited by jo_han - March 19, 2020 10:49:58

Attachments:
bool.jpg (302.9 KB)

User Avatar
Member
806 posts
Joined: Oct. 2016
Offline
I think those internal faces aren't considered “internal” by the boolean tool because a ray cast offset from their normal would count an even number of crossings. To be considered “internal”, an odd count would be required.
You may have to write your own “visual boolean” tool or maybe use a wrapping technique *1 (even if that might smoothen out creases).

Marc



*1 e.g. the shrinkwrap SOP
Edited by malbrecht - March 19, 2020 11:10:49
---
Out of here. Being called a dick after having supported Houdini users for years is over my paygrade.
I will work for money, but NOT for "you have to provide people with free products" Indie-artists.
Good bye.
https://www.marc-albrecht.de [www.marc-albrecht.de]
User Avatar
Member
3 posts
Joined: July 2019
Offline
malbrecht
You may have to write your own “visual boolean” tool

Could you maybe direct me a little, how could I go about that?
User Avatar
Member
806 posts
Joined: Oct. 2016
Offline
The first thing that came to mind for me was the shrink wrap tool. That creates a mesh on the convex “outer points”. You could subdivide that a few times, add a wrangle over points and cast a ray in each point's reverse normal direction to “hit” the underlying geometry, then move the point to that hit-point.
With the stone-geometry you have that might work well enough, with highly complex geometry (deep creases/concave areas) it's probably not the best approach. But it's “cheap”

Marc
---
Out of here. Being called a dick after having supported Houdini users for years is over my paygrade.
I will work for money, but NOT for "you have to provide people with free products" Indie-artists.
Good bye.
https://www.marc-albrecht.de [www.marc-albrecht.de]
  • Quick Links