Skinning and Animations - WebGL Game Development - page 307

Set the object's matrixWorldNeedsUpdate value to true so that updateWorldMatrix
of the bone calculates our new skinMatrix .
object.matrixAutoUpdate = true;
object.matrixWorldNeedsUpdate = true;
Calculate scale to interpolate between the prevKey and nextKey values.
scale = ( currentTime - prevKey.time ) /
( nextKey.time - prevKey.time );
prevXYZ = prevKey[ type ];
nextXYZ = nextKey[ type ];
if ( scale < 0 || scale > 1 ) {
scale = scale < 0 ? 0 : 1;
}
If the type value equals position, calculate the new position between the preyKey
and nextKey values and update the bones' position vector with the new interpolated
value. Thus, we interpolate based on the value of scale . We use spherical linear
interpolation to calculate the new quaternion between prevKey and nextKey .
if ( type === "pos" ) {
vector = object.position;
vector.x = prevXYZ[ 0 ] +
( nextXYZ[ 0 ] - prevXYZ[ 0 ] ) * scale;
vector.y = prevXYZ[ 1 ] +
( nextXYZ[ 1 ] - prevXYZ[ 1 ] ) * scale;
vector.z = prevXYZ[ 2 ] +
( nextXYZ[ 2 ] - prevXYZ[ 2 ] ) * scale;
} else if ( type === "rot" ) {
quat.slerp(object.quaternion, prevXYZ, nextXYZ, scale );
} else if ( type === "scl" ) {
vector = object.scale;
vector.x = prevXYZ[ 0 ] +
( nextXYZ[ 0 ] - prevXYZ[ 0 ] ) * scale;
vector.y = prevXYZ[ 1 ] +
( nextXYZ[ 1 ] - prevXYZ[ 1 ] ) * scale;
vector.z = prevXYZ[ 2 ] +
( nextXYZ[ 2 ] - prevXYZ[ 2 ] ) * scale;
}
}
}
};