Questions about MassNormal

Jul 15, 2010 at 6:28 PM

Hello all,

I have been browsing around Arbiter and Body recently, trying to get a better handle on how Farseer resolves collisions internally.  Specifically, I am trying to discern how it creates the Impulses which are applied to bodies.  The one part that is really throwing me for a loop is this "mass normal" value which is stored in the Contact, and later used to generate the normal impulse. 

The mass normal appears to start as a summation of the inverse mass, and the inverse moment of inertia times the tangent distance from body to contact point squared for both bodies.  Then, this whole value is inverted.  Could anybody tell me what forumla this is derrived from?  I am guessing that this is supposed to represent a "combined mass of impact along the contact normal", but I am befuddled as to how this relates to the equations I am used to seeing for force, torque, etc.  I would greatly appreciate any insight!

Thanks much!

Jul 15, 2010 at 7:29 PM

Hmm, I believe I may have found what I was looking for!

That equation at the bottom of "Impulse Based Reaction Model" looks awfully familiar :)