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Docs: Skin weight and skin index clarification #7719

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Dec 2, 2015
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Docs: Skin weight and skin index clarification #7719

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30 changes: 23 additions & 7 deletions docs/api/core/Geometry.html
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Expand Up @@ -96,16 +96,32 @@ <h3>[property:Array morphNormals]</h3>

<h3>[property:Array skinWeights]</h3>
<div>
Array of [page:Vector4 Vector4s] representing the skinning weights as used in a [page:SkinnedMesh],
The weights match the number and order of vertices in the geometry. The weighted values
are typically between the values of 0 and 1 and affect the amount that the individuals bones affect
a given vertex.
When working with a [page:SkinnedMesh], each vertex can have up to 4 [page:Bone bones] affecting it.
The skinWeights property is an array of weight values that correspond to the order of the vertices in
the geometry. So for instance, the first skinWeight would correspond to the first vertex in the geometry.
Since each vertex can be modified by 4 bones, a [page:Vector4] is used to represent the skin weights
for that vertex.
</div>
<div>
The values of the vector should typically be between 0 and 1. For instance when set to 0 the bone
transformation will have no affect. When set to 0.5 it will have 50% affect. When set to 100%, it will
have 100% affect. If there is only 1 bone associated with the vertex then you only need to worry about
the first component of the vector, the rest can be ignored and set to 0.
</div>

<h3>[property:Array skinIndices]</h3>
<div>
Array of [page:Vector4 Vector4s] representing the indices of individual bones in the [page:Skeleton.bones] array,
The indices match the number and order of vertices in the geometry.
Just like the skinWeights property, the skinIndices' values correspond to the geometry's vertices.
Each vertex can have up to 4 bones associated with it. So if you look at the first vertex, and the
first skinIndex, this will tell you the bones associated with that vertex. For example the first vertex
could have a value of <strong>( 10.05, 30.10, 12.12 )</strong>. Then the first skin index could have the
value of <strong>( 10, 2, 0, 0 )</strong>. The first skin weight could have the value of
<strong>( 0.8, 0.2, 0, 0 )</strong>. In affect this would take the first vertex, and then the bone
<strong>mesh.bones[10]</strong> and apply it 80% of the way. Then it would take the bone <strong>skeleton.bones[2]</strong>
and apply it 20% of the way. The next two values have a weight of 0, so they would have no affect.
</div>
<div>
In code another example could look like this:
<code>
// e.g.
geometry.skinIndices[15] = new THREE.Vector4( 0, 5, 9, 0 );
Expand All @@ -118,7 +134,7 @@ <h3>[property:Array skinIndices]</h3>
skeleton.bones[0]; // weight of 0.2
skeleton.bones[5]; // weight of 0.5
skeleton.bones[9]; // weight of 0.3
skeleton.bones[0]; // weight of 0
skeleton.bones[10]; // weight of 0
</code>
</div>

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