Wikis / ModelEngine 4 / Skills / Mechanics / I K

I K

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Description

Configure inverse kinematics chains, joint limits and physics bones. Changes are saved with the model.

Chain settings (enabled, alwaysactive, lockrotation, weight, blendticks) are read from the bone that controls the chain:

  • the null object of a Blockbench IK chain,
  • the tip bone of a chain made with IKChain,
  • the last link of a jig chain.

Joint limits and physics settings apply to the bone they are set on.

Attributes

Attribute Aliases Description Type Default
modelid m, mid, model Targeted model String
partid p, pid, part Targeted bone.
If not set, configures every IK bone of the model, including jig bones		 String
enabled e, en Turns the chain on or off.
If not set, use the last value		 Boolean
alwaysactive a, always Keeps a Blockbench IK chain active even when no playing animation moves its null object.
If not set, use the last value		 Boolean
lockrotation l, lock Keeps the animated rotation of the chain's tip bone, like Blockbench's "Lock IK Target Rotation".
If not set, use the last value		 Boolean
weight w How much the chain overrides the animation, from 0 to 1.
1 by default.
If not set, use the last value		 Float
blendticks bt, blend Ticks taken to blend to or away from a target set by IKTarget.
5 by default.
If not set, use the last value		 Integer
limits lim, limit Set to false to remove the joint limits of the bone Boolean
minx The minimum rotation of the joint on the X axis, in Blockbench degrees Float
maxx The maximum rotation of the joint on the X axis, in Blockbench degrees Float
miny The minimum rotation of the joint on the Y axis, in Blockbench degrees Float
maxy The maximum rotation of the joint on the Y axis, in Blockbench degrees Float
minz The minimum rotation of the joint on the Z axis, in Blockbench degrees Float
maxz The maximum rotation of the joint on the Z axis, in Blockbench degrees Float
stiffness stiff Physics: how fast a jig bone returns to its animated pose, from 0.01 to 1.
If not set, use the last value		 Float
damping damp Physics: how fast a jig bone stops swinging, from 0.01 to 1.
If not set, use the last value		 Float
gravity grav Physics: gravity on a jig bone, in blocks per second squared.
If not set, use the last value		 Float
maxangle angle Physics: how far a jig bone can swing away from its animated pose in any direction, in degrees, from 0 to 180. Per-axis limits from the tag still apply.
If not set, use the last value		 Float
repeatjig Physics: how many links a repeated jig bone becomes, see Repeating a link. Not named repeat because that is the universal mechanic attribute that repeats the whole mechanic.
If not set, use the last value		 Integer
repeatjigat Physics: where a repeated jig bone gains or loses links when repeatjig changes. end changes the far end of the chain all at once. start adds or removes one link per tick where the chain hangs from, so the far end and anything tied to it stay where they are, like reeling a rope in or out.
end by default.
If not set, use the last value		 String
exactmatch em, exact, match Should the part match the partid completely Boolean true

Unset joint limit axes keep their current value. If the bone had no limits yet, they are free.

Examples

Let the arm only follow its null object at half strength, and blend to new targets over 10 ticks:

  Skills:
    - ik{p=arm_target;w=0.5;bt=10} @self ~onSpawn

Stop a knee from bending backwards:

  Skills:
    - ik{p=knee;minx=0;maxx=140} @self ~onSpawn

Make a repeated rope 24 links long, for example while throwing it:

  Skills:
    - ik{p=rope_segment;repeatjig=24} @self

Reel the rope back in to 4 links from where it hangs, while its tied end stays on the target:

  Skills:
    - ik{p=rope_segment;repeatjig=4;repeatjigat=start} @self

Make every bone whose name contains rope heavier and looser:

  Skills:
    - ik{p=rope;em=false;grav=30;damp=0.05} @self ~onSpawn

Aliases

  • inversekinematics
Updated Oct 17, 2026