Character Collision test is misleading/incorrect.

Regarding the section of code below this comment:

// Square made from edges notice how the edges are shrunk to account
// for the polygon radius. This makes it so the square character does
// not get snagged. However, ray casts can now go through the cracks.

This doesn't work.  The snags come from the collision between the shape & 
the vertex of the edge (collision normal is tangent to line), so sinking 
them back doesn't fix anything.

What steps will reproduce the problem?
1. Instead of creating 1 sunken box, create 4 so you can see the 
interation between them.
2. Turn on Collision normal visualization
3. Drag the box along the top edge.

What is the expected output? What do you see instead?
The comment makes it sound like 'sinking' the edges should fix the snags 
but as you can see from the attached picture it does not.

What version of the product are you using? On what operating system?
r73 on Win7

Please provide any additional information below.
I think the easiest way to fix this would be with a collision filter, but 
I haven't tried this yet.

Original issue reported on code.google.com by brandon....@gmail.com on 3 Apr 2010 at 5:36

Merged into: #107

Attachments:

box2dbug.png

behdad / box2d

Character Collision test is misleading/incorrect. #110