Help Getting the force acting on a Rod

[josemendez]

Actually, one more question; I don't quite understand the mathematics here well enough to know.

When reading the lambdas (Lagrange multipliers) of the StretchShear/BendTwist constraints, I see that the values flip between negatives & positives depending on the way the rod is bending. Does this mean I should be taking the absolute values when attempting to sum the total force, or should I let them counteract each other?

Forces have a direction and a magnitude. In constraint jargon, the direction is called "gradient", and the magnitude (the Lagrange multiplier) may be along the positive or the negative part of the gradient.

For instance in a stretch constraint, stretching the rod would result in positive lambda, compressing it would result in a negative lambda (if memory serves well, might be the other way around!).

So if you just want to know how "large" the force is, take the absolute value of the force.