private BSConstraint BuildConstraint(BSPrimLinkable rootPrim, BSPrimLinkable childPrim)
{
// Zero motion for children so they don't interpolate
childPrim.ZeroMotion(true);
// Relative position normalized to the root prim
// Essentually a vector pointing from center of rootPrim to center of childPrim
OMV.Vector3 childRelativePosition = childPrim.Position - rootPrim.Position;
// real world coordinate of midpoint between the two objects
OMV.Vector3 midPoint = rootPrim.Position + (childRelativePosition / 2);
DetailLog("{0},BSLinksetConstraint.BuildConstraint,taint,root={1},rBody={2},child={3},cBody={4},rLoc={5},cLoc={6},midLoc={7}",
rootPrim.LocalID,
rootPrim.LocalID, rootPrim.PhysBody.AddrString,
childPrim.LocalID, childPrim.PhysBody.AddrString,
rootPrim.Position, childPrim.Position, midPoint);
// create a constraint that allows no freedom of movement between the two objects
// http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=4818
BSConstraint6Dof constrain = new BSConstraint6Dof(
PhysicsScene.World, rootPrim.PhysBody, childPrim.PhysBody, midPoint, true, true );
// PhysicsScene.World, childPrim.BSBody, rootPrim.BSBody, midPoint, true, true );
/* NOTE: below is an attempt to build constraint with full frame computation, etc.
* Using the midpoint is easier since it lets the Bullet code manipulate the transforms
* of the objects.
* Code left for future programmers.
// ==================================================================================
// relative position normalized to the root prim
OMV.Quaternion invThisOrientation = OMV.Quaternion.Inverse(rootPrim.Orientation);
OMV.Vector3 childRelativePosition = (childPrim.Position - rootPrim.Position) * invThisOrientation;
// relative rotation of the child to the parent
OMV.Quaternion childRelativeRotation = invThisOrientation * childPrim.Orientation;
OMV.Quaternion inverseChildRelativeRotation = OMV.Quaternion.Inverse(childRelativeRotation);
DetailLog("{0},BSLinksetConstraint.PhysicallyLinkAChildToRoot,taint,root={1},child={2}", rootPrim.LocalID, rootPrim.LocalID, childPrim.LocalID);
BS6DofConstraint constrain = new BS6DofConstraint(
PhysicsScene.World, rootPrim.Body, childPrim.Body,
OMV.Vector3.Zero,
OMV.Quaternion.Inverse(rootPrim.Orientation),
OMV.Vector3.Zero,
OMV.Quaternion.Inverse(childPrim.Orientation),
true,
true
);
// ==================================================================================
*/
PhysicsScene.Constraints.AddConstraint(constrain);
// zero linear and angular limits makes the objects unable to move in relation to each other
constrain.SetLinearLimits(OMV.Vector3.Zero, OMV.Vector3.Zero);
constrain.SetAngularLimits(OMV.Vector3.Zero, OMV.Vector3.Zero);
// tweek the constraint to increase stability
constrain.UseFrameOffset(BSParam.LinkConstraintUseFrameOffset);
constrain.TranslationalLimitMotor(BSParam.LinkConstraintEnableTransMotor,
BSParam.LinkConstraintTransMotorMaxVel,
BSParam.LinkConstraintTransMotorMaxForce);
constrain.SetCFMAndERP(BSParam.LinkConstraintCFM, BSParam.LinkConstraintERP);
if (BSParam.LinkConstraintSolverIterations != 0f)
{
constrain.SetSolverIterations(BSParam.LinkConstraintSolverIterations);
}
return constrain;
}
