Differences between joint constraints.

[KimiZhong17]

Hi.

It seems the joints are constrained based on some base constraints, and I wonder whether my thoughts about these constraints are correct. Below is my understanding:

• LinearConstaint & AngularConstraint would strictly prevent linear or angular motion;
• Translation3Constraint & Rotation3Constraint could limit the linear and angular motion into some ranges;
• TranslationConstraint & RotationConstraint are the 2D versions of the above two.

Besides, I have some questions about the code also:

• What is the meaning of "vel (velx, vely, velz)"?
• What is the definition of an anchor point?

Thanks.