tutorials/physics/ragdoll_system

[giscus[bot]]

tutorials/physics/ragdoll_system

Introduction: Since version 3.1, Godot supports ragdoll physics. Ragdolls rely on physics simulation to create realistic procedural animation. They are used for death animations in many games. In t...

https://docs.godotengine.org/en/stable/tutorials/physics/ragdoll_system.html

[TranquilMarmot]

Note that the PhysicalBoneSimulator3D has to be both active and have physical_bones_start_simulation() called on it.

When I want to have one of my characters ragdoll, I:

• Stop calling move_and_slide() (or anything else that affects velocity)
• Call stop() on any SkeletonIK3D nodes
• Set active = false on any AnimationTrees
• Set disabled = true on any CollisionShape3Ds

☝️ that will basically disable the character completely

Then, I have to:

• Set active = true on the PhysicalBoneSimulator3D
• Call physical_bones_start_simulation() on the PhysicalBoneSimulator3D

☝️ that will actually start the ragdoll

[TranquilMarmot]

Note that by default, all the joints are set to PinJoint3D

You will likely want/need to change all of the joint types

For a better description of all the different joint types

• Joint3D: This is the base class for all the joints
• ConeTwistJoint3D: Ball-and-socket, useful for shoulders, hips, neck
• HingeJoint3D: Think of it like a door hinge, useful for elbows and knees
• PinJoint3D: Just keeps two bodies connected, leads to "crumpling" of the bones when you use it
• SliderJoint3D: Slides one body along another on a specific axis
• Generic6DOFJoint3D: Can be limited in a ton of specific ways

My advice...
For character ragdolls, make everything either a ConeTwistJoint3D or a HingeJoint3D.

For the ConeTwistJoint3Ds, I found it's best to limit the "swing span" to ~20-90 degrees and the "twist span" to ~20-45 degrees.

For HingeJoint3D, make sure to turn on "Angular Limit Enabled" under "Joint Constraints". After turning that on, you can see the angle that it's being constrained to in the viewport. You can rotate the PhysicalBone3D to change the axis where the joint is constrained and then mess around with the angles.

Some more tips...

• SAVE EARLY and SAVE OFTEN
  • At least in Godot 4.3, editing physical bones and their collision shapes is the MOST that I have ever had the editor crash on me. In configuring ~20 bones I probably had it crash 20 times which about doubled the amount of time it took to do this 😢
• You can have multiple collision shapes for each bone! Sometimes this is very useful
• Seeing the bones and joints is HARD!!! To make it easier...
  • Turn off "preview sunlight" and "preview environment"
    • There are two buttons that look like a sun and a globe in the top bar under the list of open scenes
  • Turn on "Display wireframe"
    • Click the three-dot menu in the viewport (it should say "Perspective" or "Orthogonal") to turn this on
  • Look at the model directly from each side in orthogonal view when setting up the collision shapes
    • You can do this by clicking the X/Y/Z circles in the "compass" in the top-right of the viewport
• Set up the joints first, THEN go through and set all of the collision shapes
  • Sometimes, you have to rotate a joint to get the angles right. This also rotates the collision shape, so it's a bit painful to have to change both of them all the time
• Hide all of the PhysicalBone3D nodes that you aren't actively working on, otherwise it's just WAY too busy

[andrewdirisio]

All of this was insanely helpful while tackling it for the first time. Thank you for the effort in posting this!

[almic]

I would like to suggest that you set up all the joints before you do any collision shapes, because you'll be rotating the physical bone and moving it around which will make you redo the transform of any collision shapes.

[almic]

In my case, moving any of the joints after letting Godot build them for me broke a lot of joint constraints. Do not touch the joint locations! You should just use the 6DOF mode and ensure your collision shapes aren't intersecting.

[emitc2h]

I would try to make it extra clear in this section that physical_bones_start_simulation() needs to be called on the PhysicalBoneSimulator3D node, and not on the Skeleton3D node.

[N-o-a-h-t-u-r-n-e-r]

Make sure to set the collision mask for all physical bones to 1 as well so it can scan for the ground collision (Or whatever collisions live in layer 1).

[zhysgit]

Please use the physical_bones_start_simulation() method in the script of PhysicalBoneSimulator3D now, not the Skeleton3D node. This article is out of date!

[Calinou]

Pull request opened:

• Update Ragdoll system documentation for Godot 4.5 godot-docs#11392