## Highly n00bish question

Community discussion for topics unrelated to the project.

Moderator: coordinators

### Highly n00bish question

What exactly is a convex mesh? THIS video (around 12:00) says that it involves the mesh going "inwards" - however the example that is given I find rather confusing because just a couple of vertices along the mesh...it goes inwards. Why could the part the speaker highlights not just be an extension of the curve to the lower-left? I would post over there, but they aren't too great at replying after a couple of months, and that video was posted in February.

EDIT: I know the difference between convex and concave in other contexts - lenses and stuff, but have never got the hang of it with CG.

EDIT AGAIN: After watching that part of the video again...Is the criteria (criterion?) for a mesh being convex that you can connect any vertex to any other vertex with a straight line that DOES NOT leave the "inside" of the geometry?
Pilchard123

Posts: 407
Joined: Sun Oct 30, 2011 8:05 am

### Re: Highly n00bish question

Pilchard123 wrote:After watching that part of the video again...Is the criteria (criterion?) for a mesh being convex that you can connect any vertex to any other vertex with a straight line that DOES NOT leave the "inside" of the geometry?

Pretty much yes. A convex polygon is one where you can connect any two vertices without crossing an edge. So for a mesh it means you can connect any two vertexes without crossing a face.
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Lord Crc

Posts: 4517
Joined: Sat Nov 17, 2007 2:10 pm

### Re: Highly n00bish question

Pilchard123 wrote:EDIT AGAIN: After watching that part of the video again...Is the criteria (criterion?) for a mesh being convex that you can connect any vertex to any other vertex with a straight line that DOES NOT leave the "inside" of the geometry?

Actually since the inside of a mesh sometimes doesn't exist, the definition is that you can connect any 2 points on the surface without intersecting the surface.

Jeanphi
jeanphi

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Joined: Mon Jan 14, 2008 7:21 am

### Re: Highly n00bish question

Okay, thanks.
Pilchard123

Posts: 407
Joined: Sun Oct 30, 2011 8:05 am