Problem with Terrain collisions

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Run the TerrainDemo and throw some boxes around

What is the expected output? What do you see instead?
Boxes go through the terrain

What version of the product are you using? On what operating system?
using the latest (r2716) on Windows 8.1

Please provide any additional information below.
Ok, After spending hours trying to figure out why the terrain doesn't work in 
my engine i decided to try and reproduce it in the TerrainDemo.
It turns out all i had to do was run the Terrain Demo and throw some boxes 
around and i got the exact same behavior.

Not only the boxes are unstable (and jump around on the terrain until the go to 
sleep) the BIG problem is that at some part of the terrain they just go right 
through it.

After further investigation i found out that the problem happens on some 
triangles in the terrain and from the debug draw i could see that as the box 
was hitting the triangle the contact point where generated , but instead of 
pointing away from the terrain they pointed inside the terrain and just pushed 
the box through it.

IMPORTANT : I also found out that SPHERES do not have the same problem. Sphere 
behave beautifully and they are much much more stable than the boxes, which 
means the problem is probably in the box-concave collision algorithm.

here is a little video i took of the Terrain Demo to show all this : 
http://youtu.be/zCJwxk089iM

Thanks :)

Original issue reported on code.google.com by virusfre...@gmail.com on 22 Nov 2013 at 10:20

[GoogleCodeExporter]

I have seen this issue posted on the forums frequently with no responses (going 
back a couple of years), and other posts have issues with triangle mesh shapes 
(is this just terrain or all "complex" objects?)

One person explained it as the ordering between triangle strips not being 
"smooth" (odd/even), and so in between the seams you get a reversed normal.

This problem has been a deal breaker for me sadly, as nothing works (character 
controller falls through terrain, non-characters fly up on flat terrain, flat 
boxes won't rest on flat ground and just bounce around). Great engine for basic 
physics, but still needs work on stability.

Original comment by AdventUn...@gmail.com on 17 Feb 2014 at 7:06

[GoogleCodeExporter]

I'll look into it. This is likely an issue with btHeightfieldTerrainShape. 

@AdvantUnknown, it is better to keep issues separate, if you have issues with 
btBvhTriangleMeshShape it is best to create a reproduction case and file a new 
issue.

Original comment by erwin.coumans on 19 Feb 2014 at 6:30

[GoogleCodeExporter]

moved to https://github.com/bulletphysics/bullet3/issues/57

Original comment by erwin.coumans on 30 Mar 2014 at 4:59

• Changed state: Done