Unity动画转Three.js动画

一：应用场景

在工作中，由于算法给到的动画文件是Unity的.anim格式动画文件，这个格式不能直接在Web端用Three.js引擎运行。因此需要将.anim格式的动画文件转换为Three.js的AnimationClip动画对象。

二：.ANIM格式与AnimationClip对象的差异

1. AnimationClip对象格式如下：

// AnimationClip
{duration: Number // 持续时间name: String // 名称tracks: [  // 动画所有属性的关键帧轨道数组{name: String // 关键帧轨道标识符times: Float32Array // 时间数组values: Float32Array // 与时间数组中的时间点对应的相关值interpolation: Constant // 使用的插值类型},{...}] uuid: String // 实例的uuid
}

2. Unity的.anim格式如下：

它是用YAML写的，这是一个专门用来写配置文件的语言。

注意坑点：unity的.anim用的是yaml 1.1版本, yaml现在新版是1.2.x了。解析的时候注意版本是否兼容。我用js-yaml解析的时候发现它不兼容1.1旧版了，Unity (Game Engine) Yaml parsing #100
降js-yaml版本后解决"js-yaml": "^3.6.1",

.anim格式化后的内容如下：

{"AnimationClip": {"m_ObjectHideFlags": 0,"m_CorrespondingSourceObject": {"fileID": 0},"m_PrefabInstance": {"fileID": 0},"m_PrefabAsset": {"fileID": 0},"m_Name": "Take 001","serializedVersion": 6,"m_Legacy": 0,"m_Compressed": 0,"m_UseHighQualityCurve": 1,"m_RotationCurves": [],"m_CompressedRotationCurves": [],"m_EulerCurves": [],"m_PositionCurves": [],"m_ScaleCurves": [],"m_FloatCurves": [],"m_PPtrCurves": [],"m_SampleRate": 30,"m_WrapMode": 0,"m_Bounds": {},"m_ClipBindingConstant": {},"m_AnimationClipSettings": {},"m_EditorCurves": [],"m_EulerEditorCurves": [],"m_HasGenericRootTransform": 0,"m_HasMotionFloatCurves": 0,"m_Events": []}
}

三： anim格式转AnimationClip对象格式

1. 骨骼蒙皮动画

.anim文件的时间信息很可能不是按每帧给出的，如果直接转换为AnimationClip格式，没有进行插值运算（算出每一帧的信息），这样用three.js运行起来的实际效果会卡顿。

目前从网上找了个带动画的模型，测了下效果：
模型对象里的原始AnimationClip运行效果（每秒30帧）

Unity动画转Three.js动画: 模型原始的骨骼动画效

将模型导入Unity后，生成.anim动画文件。再通过脚本将这个.anim动画文件 转换为 AnimationClip对象 的运行效果如下：（没有进行插值，缺帧导致有点卡顿）

Unity动画转Three.js动画: 转换后卡顿的骨骼动画

2. 顶点变形动画（3d捏脸）

blendshape动画的转换，没有骨骼蒙皮动画转换缺帧的问题。它只需要有初始值和末值，three.js会进行插值运算。

四：关键代码：

import * as THREE from 'three';
interface AnimationClip {name: string,duration: number,tracks: any[],uuid: string,
}const get_three_js_track_type: any = {"scale": "vector","quaternion": "quaternion","position": "vector",
}const parse_unity_curve = (curve: any, curve_type: string) => {const type = get_three_js_track_type[curve_type];const name = curve.path.split('/').slice(-1) + '.' + curve_type;const values = [];const times = [];for (let cc of curve.curve.m_Curve) {times.push(cc.time)if (curve_type == "quaternion") {values.push(cc.value.x)values.push(-cc.value.y)values.push(-cc.value.z)values.push(cc.value.w)} else if (curve_type == "position") {values.push(-cc.value.x * 100)values.push(cc.value.y * 100)values.push(cc.value.z * 100)} else if (curve_type == 'scale') {values.push(cc.value.x)values.push(cc.value.y)values.push(cc.value.z)}}// if (curve_type == "quaternion") {//   return new THREE.AnimationClip(name, times, values);// }// if (curve_type == "position") {//   return new THREE.VectorKeyframeTrack(name, times, values);// }return {type,name,times,values,}
}const getAnimateClip = (obj: any, type: string, morphTargetDictionary?: any) => {const data: any = {name: '',duration: 0,tracks: [],uuid: "18A2138E-2ABF-4B83-AA15-C1D85BCE2F76",}data.name = obj.AnimationClip.m_Name;data.duration = obj.AnimationClip.m_AnimationClipSettings.m_StopTime - obj.AnimationClip.m_AnimationClipSettings.m_StartTime;if (obj.AnimationClip.m_ScaleCurves.length > 0) {for(const curve of obj.AnimationClip.m_ScaleCurves) {data.tracks.push(parse_unity_curve(curve, "scale"));}}if (obj.AnimationClip.m_RotationCurves.length > 0) {for (const curve of obj.AnimationClip.m_RotationCurves) {data.tracks.push(parse_unity_curve(curve, "quaternion"));}}if (obj.AnimationClip.m_PositionCurves.length > 0) {for (const curve of obj.AnimationClip.m_PositionCurves) {data.tracks.push(parse_unity_curve(curve, "position"));}}if (obj.AnimationClip.m_FloatCurves.length > 0) {for (const item of obj.AnimationClip.m_FloatCurves) {let name = '';if (type === 'fbx') {name = item.path.split('/').slice(-1) + '.morphTargetInfluences[' + morphTargetDictionary[item.attribute.replace('blendShape.', '')] + ']'} else if (type === 'glb') {name = item.path.split('/').slice(-1) + '.morphTargetInfluences[' + morphTargetDictionary[item.attribute.split('.').slice(-1)[0]] + ']'}const values = [];const times = [];const firstCC = item.curve.m_Curve[0];const lastCC = item.curve.m_Curve.slice(-1)[0]times.push(firstCC.time);times.push(lastCC.time);values.push(/e-/.test(firstCC.value) ? 0 : (firstCC.value / 100))values.push(/e-/.test(lastCC.value) ? 0 : (lastCC.value / 100))const track = new THREE.NumberKeyframeTrack(name, times, values);data.tracks.push(track)}}return data;
}export {getAnimateClip,
}