On Sunday, June 26, 2011 17:27:06 xsaint wrote:
> Hello All...
> I am trying to better understand how YASIM calculates its contacts
Hi there, I'll try to answer, see below:
> 1) As from my experience, the SIM crashes when some part of the wings
> comes in contact with a building or ground and it does not crash if
> other parts of the wings hit the ground of a building.The wing
> specification is correct in FDM as checked againts the blender script.
> So how does it deduce the contact points?
There might be a difference between regular collision detection provided by
the FG engine itself, about which I have no information, and YASim _ground_
collision detection. The latter is implemented as follows:
Contact points (internally represented as gear objects but with special
properties and hardcoded values for friction) are compiled from the wingtips
and the fore and aft tips of the fuselage. These contact points will hold at
full compression 10 times the plane's mass.
So for a conventional airplane there will be two contact points for the
fuselage (nose and tail), the main wing tips, the tips of the horizontal and
vertical stabiliser. Any collision detected with these contact points will be
treated by YASim as a special case of gear collision and compared to the force
> 2) Eventhough CG looks like it is in correct place, in YASIM, the plane
> do sink to the ground before take off. Insufficient lift maybe.... but
> the back of the fuselage do sink into the runway. As such, as
> possibility of implementing tail strikes?
It is possible that either the aft end of the fuselage as defined in XML is
higher than the lowest part of the model, or that the mass which it has to
sustain is larger than the spring compression of the contact point can
sustain. You can try to compensate the first issue by placing a fake gear
object at the lowest point where the fuselage touches the ground.
> Much all appreciate all valuable replies and also if you could point me
> towards any valuable YASIM documents.
There is a technical document floating on the web, can't quite remember where
but try to google YASim-simnotes.pdf
Other than that, your best reference is the source code.
Hope it helps,