Three.js 皮肤指数和皮肤重量的含义是什么？

这是无证的，所以我在这里问。我正在尝试用JavaScript制作网格动画。我使用Blender->Three.js exporter是因为它很方便。我无法使用Three.js本身，因为我无法解决它的某些问题（将带有动画网格的场景的法线和深度信息渲染到缓冲区）。那么，如何读取从Blender导出到Three.js的“SkinIndex”和“skinWeights”属性呢？它们是什么意思？它们在计算动画上顶点的位置时扮演什么角色

"bones" : [
    {"parent":-1,"name":"pelvis","pos":[-3.52132e-08,0.0410043,0.880063],"rotq":[0,0,0,1]},
    {"parent":0,"name":"thigh.L","pos":[0.0878887,0.00522349,0.102822],"rotq":[0,0,0,1]},
    {"parent":1,"name":"shin.L","pos":[0.103679,0.00638392,-0.445744],"rotq":[0,0,0,1]},
    {"parent":2,"name":"foot.L","pos":[0.0655578,0.0194668,-0.418675],"rotq":[0,0,0,1]},
    {"parent":3,"name":"toe.L","pos":[0.0280578,-0.107185,-0.0704246],"rotq":[0,0,0,1]},
    {"parent":3,"name":"heel.L","pos":[3.58224e-05,0.036576,-0.0885088],"rotq":[0,0,0,1]},
    {"parent":0,"name":"thigh.R","pos":[-0.0878888,0.00522352,0.102822],"rotq":[0,0,0,1]},
    {"parent":6,"name":"shin.R","pos":[-0.103679,0.00638412,-0.445745],"rotq":[0,0,0,1]},
    {"parent":7,"name":"foot.R","pos":[-0.0655576,0.0194677,-0.418675],"rotq":[0,0,0,1]},
    {"parent":8,"name":"toe.R","pos":[-0.0280577,-0.107185,-0.0704248],"rotq":[0,0,0,1]},
    {"parent":8,"name":"heel.R","pos":[-3.57926e-05,0.036576,-0.0885083],"rotq":[0,0,0,1]},
    {"parent":0,"name":"stomach","pos":[5.37268e-09,-0.008465,0.121596],"rotq":[0,0,0,1]},
    {"parent":11,"name":"chest","pos":[1.94616e-08,0.0538289,0.269019],"rotq":[0,0,0,1]},
    {"parent":12,"name":"upper_arm.L","pos":[0.160045,-0.010388,0.159844],"rotq":[0,0,0,1]},
    {"parent":13,"name":"forearm.L","pos":[0.165089,0.0102809,-0.232678],"rotq":[0,0,0,1]},
    {"parent":14,"name":"hand.L","pos":[0.0980782,-0.0148839,-0.245313],"rotq":[0,0,0,1]},
    {"parent":15,"name":"index.L.001","pos":[0.019191,-0.040475,-0.0743723],"rotq":[0,0,0,1]},
    {"parent":16,"name":"index.L.002","pos":[-0.00562334,-0.00824448,-0.0310695],"rotq":[0,0,0,1]},
    {"parent":17,"name":"index.L.003","pos":[-0.00953785,-0.00126594,-0.0192741],"rotq":[0,0,0,1]},
    {"parent":15,"name":"middle.L.001","pos":[0.0191911,-0.0188201,-0.0769786],"rotq":[0,0,0,1]},
    {"parent":19,"name":"middle.L.002","pos":[0.00288424,-0.00695575,-0.0326532],"rotq":[0,0,0,1]},
    {"parent":20,"name":"middle.L.003","pos":[-0.0111618,-0.00550338,-0.0242877],"rotq":[0,0,0,1]},
    {"parent":15,"name":"ring.L.001","pos":[0.0186397,0.00194495,-0.0777299],"rotq":[0,0,0,1]},
    {"parent":22,"name":"ring.L.002","pos":[0.00393239,-0.00062982,-0.0309386],"rotq":[0,0,0,1]},
    {"parent":23,"name":"ring.L.003","pos":[-0.00873661,-0.00165674,-0.024165],"rotq":[0,0,0,1]},
    {"parent":15,"name":"pinky.L.001","pos":[0.0191911,0.02271,-0.0758559],"rotq":[0,0,0,1]},
    {"parent":25,"name":"pinky.L.002","pos":[-0.0057596,0.0014303,-0.0236881],"rotq":[0,0,0,1]},
    {"parent":26,"name":"pinky.L.003","pos":[-0.00877053,-0.0020119,-0.0195478],"rotq":[0,0,0,1]},
    {"parent":15,"name":"thumb.L.001","pos":[-0.0073517,-0.0318671,-0.0156776],"rotq":[0,0,0,1]},
    {"parent":28,"name":"thumb.L.002","pos":[-0.00941652,-0.0166059,-0.0179188],"rotq":[0,0,0,1]},
    {"parent":29,"name":"thumb.L.003","pos":[-0.0081799,-0.0129757,-0.0276645],"rotq":[0,0,0,1]},
    {"parent":12,"name":"upper_arm.R","pos":[-0.160044,-0.010388,0.159844],"rotq":[0,0,0,1]},
    {"parent":31,"name":"forearm.R","pos":[-0.165089,0.0102809,-0.232679],"rotq":[0,0,0,1]},
    {"parent":32,"name":"hand.R","pos":[-0.0980774,-0.0148839,-0.245313],"rotq":[0,0,0,1]},
    {"parent":33,"name":"index.R.001","pos":[-0.0185038,-0.0404748,-0.0743726],"rotq":[0,0,0,1]},
    {"parent":34,"name":"index.R.002","pos":[0.00562337,-0.00824449,-0.0310695],"rotq":[0,0,0,1]},
    {"parent":35,"name":"index.R.003","pos":[0.00953785,-0.00126596,-0.0192741],"rotq":[0,0,0,1]},
    {"parent":33,"name":"middle.R.001","pos":[-0.0185038,-0.0188199,-0.0769789],"rotq":[0,0,0,1]},
    {"parent":37,"name":"middle.R.002","pos":[-0.00288421,-0.00695577,-0.0326532],"rotq":[0,0,0,1]},
    {"parent":38,"name":"middle.R.003","pos":[0.0111619,-0.00550339,-0.0242877],"rotq":[0,0,0,1]},
    {"parent":33,"name":"ring.R.001","pos":[-0.0179525,0.00194514,-0.0777302],"rotq":[0,0,0,1]},
    {"parent":40,"name":"ring.R.002","pos":[-0.00393245,-0.000629827,-0.0309386],"rotq":[0,0,0,1]},
    {"parent":41,"name":"ring.R.003","pos":[0.00873658,-0.00165676,-0.024165],"rotq":[0,0,0,1]},
    {"parent":33,"name":"pinky.R.001","pos":[-0.0185039,0.0227101,-0.0758562],"rotq":[0,0,0,1]},
    {"parent":43,"name":"pinky.R.002","pos":[0.0057596,0.00143027,-0.0236881],"rotq":[0,0,0,1]},
    {"parent":44,"name":"pinky.R.003","pos":[0.00877053,-0.00201192,-0.0195478],"rotq":[0,0,0,1]},
    {"parent":33,"name":"thumb.R.001","pos":[0.00803882,-0.0318669,-0.0156779],"rotq":[0,0,0,1]},
    {"parent":46,"name":"thumb.R.002","pos":[0.00941664,-0.0166059,-0.0179188],"rotq":[0,0,0,1]},
    {"parent":47,"name":"thumb.R.003","pos":[0.00817987,-0.0129757,-0.0276645],"rotq":[0,0,0,1]},
    {"parent":12,"name":"neck","pos":[1.6885e-08,-0.0164749,0.225555],"rotq":[0,0,0,1]},
    {"parent":49,"name":"head","pos":[0.000806741,-0.0273245,0.0637051],"rotq":[0,0,0,1]}],

"skinIndices" : [
        11,0,11,0,1,11,11,0,0,11,0,11,1,11,1,11,0,11,11,0,11,0,11,0,1,11,11,0,11,0,0,11,1,11,1,11,0,11,0,11,0,11,12,0,0,11,0,11,
        0,11,12,0,12,0,11,0,11,0,11,0,12,0,11,0,11,0,11,0,12,0,12,11,11,0,11,0,12,13,11,0,0,11,11,0,12,13,12,13,0,11,12,13,12,0,
        12,0,13,12,13,12,12,13,12,0,12,13,13,12,12,13,12,13,13,12,13,0,12,13,12,0,12,13,13,0,12,0,13,0,0,13,13,0,13,0,0,13,0,13,
        13,0,13,0,0,13,13,12,13,12,13,12,13,0,13,0,13,0,13,12,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,0,13,
        (... too big)]

"skinWeights" : [
    0.454566,0.443267,0.456435,0.4405,0.568642,0.331477,0.452697,0.446034,0.600277,0.577654,0.603738,0.578153,0.557686,0.334716,
    0.579597,0.328238,0.596817,0.577156,0.481496,0.447683,0.604872,0.59171,0.466162,0.448242,0.567426,0.35812,0.49683,0.447124,
    0.618979,0.590887,0.592533,0.590764,0.578989,0.341559,0.555862,0.37468,0.477411,0.438341,0.617349,0.569542,0.454728,0.432345,
    0.401061,0.337472,0.500093,0.444338,0.633534,0.572105,0.601164,0.56698,0.388198,0.308292,0.413925,0.366652,0.449179,0.424051,
    0.618298,0.58735,0.458406,0.430254,0.473939,0,0.439952,0.417849,0.605333,0.579977,0.631263,0.594722,0.517687,0,0.430191,0.274572,
    (... too big)]


"animations" : [
    {"name":"ArmatureAction",
    "fps":24,
    "length":0.625,
    "hierarchy":
    [{"parent":-1,"keys":[
        {"time":0,"pos":[-3.52132e-08,0.0410043,0.880063],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[-3.52132e-08,0.0410043,0.880063]},
        {"time":0.625,"pos":[-3.52132e-08,0.0410043,0.880063],"rot":[0,0,0,1],"scl":[1,1,1]}]
    },
    {"parent":0,"keys":[
        {"time":0,"pos":[0.0878887,0.00522349,0.102822],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[0.0878887,0.00522349,0.102822],"rot":[-0.36166,-1.53668e-08,-7.05768e-10,0.93231]},
        {"time":0.625,"pos":[0.0878887,0.00522349,0.102822],"rot":[0,0,0,1],"scl":[1,1,1]}
    ]},
    {"parent":1,"keys":[
        {"time":0,"pos":[0.103679,0.00638392,-0.445744],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[0.103679,0.00638392,-0.445744]},
        {"time":0.625,"pos":[0.103679,0.00638392,-0.445744],"rot":[0,0,0,1],"scl":[1,1,1]}
    ]},
    {"parent":2,"keys":[
        {"time":0,"pos":[0.0655578,0.0194668,-0.418675],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[0.0655578,0.0194668,-0.418675]},
        {"time":0.625,"pos":[0.0655578,0.0194668,-0.418675],"rot":[0,0,0,1],"scl":[1,1,1]}
    ]},
    {"parent":3,"keys":[
        {"time":0,"pos":[0.0280578,-0.107185,-0.0704246],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[0.0280578,-0.107185,-0.0704246]},
        {"time":0.625,"pos":[0.0280578,-0.107185,-0.0704246],"rot":[0,0,0,1],"scl":[1,1,1]}
    ]},
    {"parent":4,"keys":[
        {"time":0,"pos":[3.58149e-05,0.036576,-0.0885088],"rot":[0,0,0,1],"scl":[1,1,1]},
        {"time":0.291667,"pos":[3.58149e-05,0.036576,-0.0885088]},
        {"time":0.625,"pos":[3.58149e-05,0.036576,-0.0885088],"rot":[0,0,0,1],"scl":[1,1,1]}
    ]},

---

每个顶点对应一个蒙皮索引，该索引对应一个蒙皮权重。蒙皮索引是特定顶点受其影响的骨骼的索引（每个顶点只能属于一个骨骼）。蒙皮权重是骨骼对该顶点的影响量。

蒙皮索引和

蒙皮权重

属性是数组的数组（从技术上讲，内部数组是三个.js

Vector4

对象）。其中一个的外部数组中的每个项根据索引位置与网格中的每个顶点一一对应

从three.js JSON模型文件创建这些属性的值：

if ( json.skinWeights ) {

    for ( var i = 0, l = json.skinWeights.length; i < l; i += influencesPerVertex ) {

        var x = json.skinWeights[ i ];
        var y = ( influencesPerVertex > 1 ) ? json.skinWeights[ i + 1 ] : 0;
        var z = ( influencesPerVertex > 2 ) ? json.skinWeights[ i + 2 ] : 0;
        var w = ( influencesPerVertex > 3 ) ? json.skinWeights[ i + 3 ] : 0;

        geometry.skinWeights.push( new Vector4( x, y, z, w ) );

    }

}

if ( json.skinIndices ) {

    for ( var i = 0, l = json.skinIndices.length; i < l; i += influencesPerVertex ) {

        var a = json.skinIndices[ i ];
        var b = ( influencesPerVertex > 1 ) ? json.skinIndices[ i + 1 ] : 0;
        var c = ( influencesPerVertex > 2 ) ? json.skinIndices[ i + 2 ] : 0;
        var d = ( influencesPerVertex > 3 ) ? json.skinIndices[ i + 3 ] : 0;

        geometry.skinIndices.push( new Vector4( a, b, c, d ) );

    }
}

---

看起来它们与混合器顶点组和权重相对应。每个骨骼都有一个移动的顶点组，该组中的每个顶点都有一定的影响百分比。查看生成索引和权重，如果js动画文件中的SkinIndex和skinWeights都是零，这是否好？。。。

// e.g.
geometry.skinIndices[15] = new THREE.Vector4(   0,   5,   9, 0 );
geometry.skinWeights[15] = new THREE.Vector4( 0.2, 0.5, 0.3, 0 );

// corresponds with the following vertex
geometry.vertices[15];

// these bones will be used like so:
skeleton.bones[0]; // weight of 0.2
skeleton.bones[5]; // weight of 0.5
skeleton.bones[9]; // weight of 0.3
skeleton.bones[10]; // weight of 0