yade-dev team mailing list archive

[noreply@xxxxxxxxxxxxx]

------------------------------------------------------------
revno: 2567
committer: jduriez <jduriez@c1solimara-l>
branch nick: yade
timestamp: Tue 2010-11-23 18:26:38 +0100
message:
  Details changes in comments of Vector3r forcesOnPlane(..), after http://www.mail-archive.com/yade-users@xxxxxxxxxxxxxxxxxxx/msg02610.html. Hoping you agree, Vaclav (if not, do not hesitate to revert !)
modified:
  py/_utils.cpp


--
lp:yade
https://code.launchpad.net/~yade-dev/yade/trunk

Your team Yade developers is subscribed to branch lp:yade.
To unsubscribe from this branch go to https://code.launchpad.net/~yade-dev/yade/trunk/+edit-subscription

=== modified file 'py/_utils.cpp'
--- py/_utils.cpp	2010-11-07 11:46:20 +0000
+++ py/_utils.cpp	2010-11-23 17:26:38 +0000
@@ -354,7 +354,8 @@
 /* Find all interactions deriving from NormShearPhys that cross plane given by a point and normal
 	(the normal may not be normalized in this case, though) and sum forces (both normal and shear) on them.
 	
-	Return a 3-tuple with the components along global x,y,z axes.
+	Returns a 3-tuple with the components along global x,y,z axes, which can be viewed as "action from lower part, towards
+	upper part" (lower and upper parts with respect to the plane's normal).
 
 	(This could be easily extended to return sum of only normal forces or only of shear forces.)
 */
@@ -370,9 +371,10 @@
 		if(d3dg){ pos1=d3dg->se31.position; pos2=d3dg->se32.position; }
 		else{ pos1=Body::byId(I->getId1(),scene)->state->pos; pos2=Body::byId(I->getId2(),scene)->state->pos; }
 		Real dot1=(pos1-planePt).dot(normal), dot2=(pos2-planePt).dot(normal);
-		if(dot1*dot2>0) continue; // both interaction points on the same side of the plane
+		if(dot1*dot2>0) continue; // both (centers of) bodies are on the same side of the plane=> this interaction has to be disregarded
 		// if pt1 is on the negative plane side, d3dg->normal.Dot(normal)>0, the force is well oriented;
-		// otherwise, reverse its contribution
+		// otherwise, reverse its contribution. So that we return finally
+		// Sum [ ( normal(plane) dot normal(interaction= from 1 to 2) ) "nsi->force" ]
 		ret+=(dot1<0.?1.:-1.)*(nsi->normalForce+nsi->shearForce);
 	}
 	return ret;