Change KinematicBody to RigidBody or behave like one

peterpop

Ok, so I have read a large number of posts different places explaining what you use the different nodes for. I quite understand those - I think I do at least.

But I need some help figuring this one out: I am making a tilt tray sorter simulation. That means that items (e.g. parcels/boxes) are put onto trays that are moving along a conveyor like rail. When the item has reached its destination the tray is tilted so the item slides of. My trays are made of two objects; a base and a tray. The tray has animations for tilting left and right. In code I instantiate an item as a child to the tray. I do that so the item moves along with the tray, and also tilts along when the tray tilts. The items have a root node of KinematicBody. This is first and foremost because I am not allowed to make a Rigidbody a child of a moving object (the tray). So far so good. The items are moving along with the trays. But when the tray is tilted (i.e. the tilt animation has stopped) I want the item to slide of the tray, but also not be a child of the tray, but the main scene. At this point I want to change the KinematicBody to a RigidBody because then all movement of the item would be taken care of by the engine (and I don't need precise control of it anymore). But it does not look like there is an "easy" way to accomplish this. Can anybody help with suggestions?

peterpop

I managed to solve it by having two almost identical nodes - one for KinematicBody and one for RigidBody - and then swap them at the right time. This, however, created a new problem where there is a small pause at the swapping moment. I have described it in this reddit post: https://www.reddit.com/r/godot/comments/flx9hq/replacing_moving_kinematicbody_with_rigidbody/?utm_source=share&utm_medium=web2x

Erich_L

I'm curious, did you try keep the objects on the tray just as a rigid body? If you want to keep them from falling on their side, you could try an Axis lock. The axis lock could be toggled off when the item needs to get dropped off

dotted

You could experiment with a rigid-body in kinematic mode, then changing it when you need RIGID-BODY behavior.

However, I use the following design to make physics based 'kinematic bodies', which is simple. Your kinematic body controls a rigid-body via joint. I recommend using 'stiff' springs and it allows (i would assume bullet) rigid-body to behave well.

I recommend creating a scene to package up the scheme like so:

Spatial (ConveyorAssembly) KinematicBody (Your tray) RigidBody (Your parcel) * Joint (Glue to hold the parcel to the tray)

So just before you tilt the tray, remove the joint. Or remove the joint somewhere during the tilting if it lends to some desirable creative effect.