How to get a 2d slice of 3d geometry?

Forums Technical Discussion How to get a 2d slice of 3d geometry?

3765 8 2


anon_user_95676451: Member; 39 posts; Joined: Oct. 2017; Offline

Jan. 21, 2018 5:46 p.m.

Basically like the “clip” SOP but it outputs a single polygon, or the volume slice SOP except for geometry. Thanks.


mestela: Member; 1746 posts; Joined: May 2006; Online

Jan. 21, 2018 6:26 p.m.

I'm sure you'll get 20 answers from 20 different artists!

My lazy way is to use the voronoi fracture. Feed a pig to the left input, a straight line with lots of divisions to the center input, you get sliced ham out the other end, just blast/split the one you want to keep.

Attachments:
sliced_ham.gif (420.9 KB)

http://www.tokeru.com/cgwiki [www.tokeru.com]
https://www.patreon.com/mattestela [www.patreon.com]


tamte: Member; 8599 posts; Joined: July 2007; Offline

Jan. 21, 2018 7:20 p.m.

if you started with closed geo
then Clip + Divide(Remove Shared Edges) + Hole should do the trick
or Boolean (Intersect) with a plane (A Solid, B Surface)

Tomas Slancik
FX Supervisor
Method Studios, NY


anon_user_95676451: Member; 39 posts; Joined: Oct. 2017; Offline

Jan. 22, 2018 1:32 a.m.

mestela
My lazy way is to use the voronoi fracture. Feed a pig to the left input, a straight line with lots of divisions to the center input, you get sliced ham out the other end, just blast/split the one you want to keep.

This works really well and is quite ingenious, but for my purposes doesn't work very well. Thanks a bunch though, I'm sure I'll use this method sometime in the future anyway!

tamte
if you started with closed geo
then Clip + Divide(Remove Shared Edges) + Hole should do the trick
or Boolean (Intersect) with a plane (A Solid, B Surface)

This worked really well, but in both cases I get severe “scratching” artifacts as well as strange geometry behavior with Test Geometries (shader ball, Tommy) near the end of transformations like translation and rotation, especially with the Boolean method. (In both .hip files I've used the $F keyframe to control transformation)

Attachments:
tommyinflatlanddivide.hipnc (323.5 KB)
tommyinflatlandboolean.hipnc (324.2 KB)


vusta: Member; 555 posts; Joined: Feb. 2017; Offline

Jan. 22, 2018 5:13 a.m.

here are the fixes…for both versions

Boolean's archilles' heel is that…solid mode is flaky at best when your geo is not watertight

Attachments:
tommyinflatlanddivide_fix.hipnc (227.7 KB)
tommyinflatlandboolean_fix.hipnc (225.3 KB)


anon_user_95676451: Member; 39 posts; Joined: Oct. 2017; Offline

Jan. 22, 2018 6:05 a.m.

Interesting! What exactly do you mean by watertight though? As in, the geometry doesn't have any holes?

Also, IntersectionAnalysis fails for geometry whose genus is greater than 0 (i.e. a genus-1 torus (regular donut)). What can be done to fix this?


vusta: Member; 555 posts; Joined: Feb. 2017; Offline

Jan. 22, 2018 6:57 a.m.

add a fuse before polyfill, then a hole after polyfill


anon_user_95676451: Member; 39 posts; Joined: Oct. 2017; Offline

Jan. 22, 2018 8:38 a.m.

Didn't seem to work


vusta: Member; 555 posts; Joined: Feb. 2017; Offline

Jan. 22, 2018 2:34 p.m.

worked for me

Quick Links

                    
                        Search links
                        Show recent posts
                        Show unanswered posts