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General Category => General Anim8or Forum => Topic started by: selden on March 30, 2009, 12:09:23 pm

Title: bug: cuts create spurious surface extensions
Post by: selden on March 30, 2009, 12:09:23 pm
The following sequence of commands causes surfaces to extend beyond their edges. Sometimes this can be "fixed" by additional cuts, other times the cuts cause other spurious surface extensions to appear.

[edit] This bug can be seen in Anim8or v0.97d [/edit]

1. open Animator (in object edit mode)
2. create a cube primitive
3. convert to mesh
4. switch to point edit
5. make two cuts across only the top line
  there now are four points in the top line,
  call them 1,2,3,4 from left to right
6. select the two points at the top right (points 3 & 4)
7. move them upward

bug: a diagonal (grey) surface extension appears between points 1 & 3.
It's an extension of the cube's front and rear surfaces.
This should not have happened: point #2 represents the ends of an edge cut across the top of the cube between the front and rear edges.

Here's a view of the result, with the front rotated down slightly, showing the edges created by the cuts and the inappropriate diagonal extensions of the front and rear surfaces.
Title: Re: bug: cuts create spurious surface extensions
Post by: ENSONIQ5 on March 30, 2009, 01:03:37 pm
The solution to this is to remove the top face prior to cutting, then fill the three holes formed in the final mesh once the points have been manipulated.
Title: Re: bug: cuts create spurious surface extensions
Post by: Raxx on March 30, 2009, 01:14:48 pm
Ensoniq5, that's not quite the solution....

selden, this is not a bug. It's a result of you not knowing better ;)

What you have are concave faces, which do not handle well in most 3D applications. Even the manual (http://www.anim8or.com/manual/4_object_editor.html#merge_faces) has something about this.

To fix, use the knife tool and connect point #2 to the point in the bottom right corner below point #4, and likewise for the other side. This changes the n-sided polygon into two legal quads. This is one of the basics of modeling ;)

Edit: Added screenshot
Title: Re: bug: cuts create spurious surface extensions
Post by: ENSONIQ5 on March 30, 2009, 01:30:57 pm
Heh, I knew I was missing something simple!  Hey, it's late here Down Under... that's my excuse!

Thanks for the correction Raxx, nicely explained.
Title: Re: bug: cuts create spurious surface extensions
Post by: selden on March 30, 2009, 01:47:57 pm
Difficult or not, it's something point editing has to be able to handle. In complex meshes, it is not at all obvious which edges are going to be "convex" after moving points around.
Title: Re: bug: cuts create spurious surface extensions
Post by: Raxx on March 30, 2009, 02:06:02 pm
I'm sorry but you're just plain wrong. You're pretty much saying that the program has to clean up after all your messes. Don't perform sloppy modeling like everyone else and you'll be fine. If you're losing track of your model structure in a "complex mesh" then you'd better figure out a way to simplify it until you get back on track. Doing it the right way takes effort, that's why people get paid to do it so that lazy people don't have to. Either don't be lazy or wait for someone else to clean up after you.