@modoki/engine / index / PaintWeightsOptions

Interface: PaintWeightsOptions

Weight painting for 2D skinning rigs — brush a bone's influence onto mesh vertices near a point, preserving the relative proportions of other bones and renormalizing to <=4 influences per vertex. This is the computational core of the (planned) weight- paint UI: the panel supplies a brush position/radius/strength + target bone, this returns updated skinIndices/skinWeights. Pure + deterministic.

"Add" semantics (like Blender's Add weight-paint): each affected vertex's target weight moves toward 1 by t = strength·falloff, and its OTHER weights are scaled so the four still sum to 1 — so painting a bone in grows it without wiping the blend.

Skinning

boneIndex

boneIndex: number

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bonePositions?

optional bonePositions?: readonly readonly number[][]

Per-bone bind position [x,y] (same space as verts). Used by the eraser to hand the freed weight to the NEAREST other bone when the target is a vertex's SOLE influence — otherwise erasing there renormalizes straight back to 1.

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center

center: readonly [number, number]

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falloff?

optional falloff?: "constant" | "smooth"

Brush profile across the radius: 'smooth' (smoothstep falloff, default) or 'constant' (hard edge).

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mode?

optional mode?: "add" | "subtract" | "set"

'add' (default) grows the target bone's weight toward 1; 'subtract' shrinks it toward 0; 'set' blends it toward strength (used as the TARGET weight, not an intensity). Other bones rebalance to keep each vertex summing to 1.

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radius

radius: number

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skinIndices

skinIndices: readonly number[]

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skinWeights

skinWeights: readonly number[]

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strength

strength: number

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verts

verts: readonly readonly number[][]