When does getContactNormal return vec3_zero

[michael.zhang]

Hello,

 

For some reason, when my capsule collides with the corner of a box, when I check its contact normal via:

 

getContactNormal (contactNumber) using the contact number provided by the callback,

 

I get a vec3_zero.

 

It works fine in all other cases so far. What are the conditions underwhich a getContactNormal would return a zero vector?