Base node for all joint constraints in 2D physics. Base node for all joint constraints in 2D physics. Joints take 2 bodies and apply a custom constraint. When [member node_a] and [member node_b] move in different directions the [code]bias[/code] controls how fast the joint pulls them back to their original position. The lower the [code]bias[/code] the more the two bodies can pull on the joint. When set to [code]0[/code], the default value from [member ProjectSettings.physics/2d/solver/default_constraint_bias] is used. If [code]true[/code], [member node_a] and [member node_b] can not collide. The first body attached to the joint. Must derive from [PhysicsBody2D]. The second body attached to the joint. Must derive from [PhysicsBody2D].