微信小程序xr-frame实现动画

基础知识：

• 动画系统

xr-frame中所有的动画都是通过动画系统animationsystem统一管理的，在每帧的同一个时机统一更新。动画系统自身没有什么逻辑，所有的逻辑都是在动画组件animator和动画实现animation中的。

• 动画实现

1.动画json数据(类似于css)：

{
  "keyframe": {
    "cube": {
      "0": {
        "position": [-3, 0, 2]
      },
      "50": {
        "rotation": [0, 0, 0],
        "scale": [1, 1, 1]
      },
      "100": {
        "position": [3, 0, 2],
        "rotation": [0, 3.14, 0],
        "scale": [1.4, 1.4, 1.4]
      }
    },
    "sphere": {
      "0": {
        "position": [-3, 0, 0],
        "scale": [0.8, 0.8, 0.8]
      },
      "50": {
        "position": [0, 0.2, 0],
        "scale": [1, 1, 1]
      },
      "100": {
        "position": [3, 0, 0],
        "scale": [0.8, 0.8, 0.8]
      }
    },
    "cylinder": {
      "0": {
        "position": [-3, 0, -2],
        "rotation": [0, 0, 0]
      },
      "50": {
        "rotation": [0, 0, -3.14]
      },
      "100": {
        "position": [3, 0, -2],
        "rotation": [0, 0, 3.14]
      }
    },
    "plane": {
      "0": {
        "material.u_basecolorfactor": [0.48, 0.78, 0.64, 1]
      },
      "50": {
        "material.u_basecolorfactor": [0.368, 0.937, 0.176, 1]
      },
      "100": {
        "material.u_basecolorfactor": [0.176, 0.368, 0.937, 1]
      }
    },
    "spotlight": {
      "0": {
        "position": [-4, 1, -4]
      },
      "25": {
        "position": [-4.3, 0.5, -2]
      },
      "75": {
        "position": [-3, 1.5, 2]
      },
      "100": {
        "position": [-4, 1, 4]
      }
    }
  },
  "animation": {
    "default": {
      "keyframe": "cube",
      "duration": 1,
      "ease": "ease-in-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "sphere": {
      "keyframe": "sphere",
      "duration": 1,
      "ease": "ease-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "cylinder": {
      "keyframe": "cylinder",
      "duration": 1,
      "ease": "ease-in",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "plane": {
      "keyframe": "plane",
      "duration": 4,
      "ease": "linear",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "spotlight": {
      "keyframe": "spotlight",
      "duration": 2,
      "ease": "ease-in-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    }
  }
}

可以参与动画的属性：

• 属性的值为number、number-array和color类型的数据都可以进行动画，程序会自动计算关键帧之间每一帧每个属性的值应该是多少。
• 除了position、rotation、scale之外，像material.u_basecolorfactor这样的属性也可以，如下，可以改变物体的颜色。

"0": {
    "material.u_basecolorfactor": [0.48, 0.78, 0.64, 1]
},
"100": {
    "material.u_basecolorfactor": [0.176, 0.368, 0.937, 1]
}

2.引入动画（type="keyframe"）

 <xr-asset-load asset-id="basic-anim" type="keyframe" src="../basic-animation.json"/>

3.模型或者节点绑定动画

 <xr-mesh
      node-id="mesh-cube" position="-3 0 2" scale="1 1 1" rotation="0 0 0" geometry="cube" material="standard-mat" uniforms="u_basecolorfactor:0.298 0.764 0.85 1"
      anim-keyframe="basic-anim" anim-clipmap="default:cube" anim-autoplay="clip:cube, speed:2"
      cast-shadow
    ></xr-mesh>
注明:此案例用到的动画：(default：cube")
1. anim-keyframe：绑定动画的名字对应动画资源asset-id;
2. anim-clipmap:绑定动画数据中的名字;
3. anim-autoplay：
  .第一种情况不加参数：模型自身的动画;
  .第二种情况加参数：anim-autoplay对应json中的动画名，还可以指定速度;

整体代码效果(来源于：动画系统 | 微信开放文档)

• wxml部分：

<xr-scene id="xr-scene" bind:ready="handleready">
  <xr-assets bind:progress="handleassetsprogress" bind:loaded="handleassetsloaded">
    <xr-asset-load asset-id="basic-anim" type="keyframe" src="/assets/animation/basic-animation.json"/>
    <xr-asset-load type="texture" asset-id="waifu" src="/assets/waifu.png" />
    <xr-asset-material asset-id="standard-mat" effect="standard" />
  </xr-assets>
  <xr-node>
    <xr-node node-id="camera-target" position="0 0 0"></xr-node>
    <xr-mesh
      node-id="mesh-plane" position="0 -0.8 0" rotation="0 0 0" scale="10 1 8" geometry="plane" material="standard-mat" uniforms="u_basecolorfactor:0.48 0.78 0.64 1" states="cullon: false"
      anim-keyframe="basic-anim" anim-autoplay="clip:plane, speed:4"
      receive-shadow
    ></xr-mesh>
    <xr-mesh
      node-id="mesh-cube" position="-3 0 2" scale="1 1 1" rotation="0 0 0" geometry="cube" material="standard-mat" uniforms="u_basecolorfactor:0.298 0.764 0.85 1"
      anim-keyframe="basic-anim" anim-clipmap="default:cube" anim-autoplay="clip:cube, speed:2"
      cast-shadow
    ></xr-mesh>
    <xr-mesh 
      node-id="mesh-sphere" position="-3 0 0" scale="0.8 0.8 0.8" geometry="sphere" material="standard-mat" uniforms="u_basecolorfactor:0.937 0.176 0.368 1"
      anim-keyframe="basic-anim" anim-autoplay="clip:sphere, speed:2"
      cast-shadow
    ></xr-mesh>
    <xr-mesh 
      node-id="mesh-cylinder" position="-3 0 -2" scale="1 0.6 1" geometry="cylinder" material="standard-mat" uniforms="u_basecolorfactor:1 0.776 0.364 1"
      anim-keyframe="basic-anim" anim-autoplay="clip:cylinder, speed:2"
      cast-shadow
    ></xr-mesh>
    <xr-mesh node-id="mesh-light-cube" position="-5 1 0" scale="0.5 10 10" rotation="0 0 0" geometry="cube" material="standard-mat" uniforms="u_basecolorfactor:0.3 0.3 0.3 1, u_basecolormap: waifu"></xr-mesh>
    <xr-camera
      id="camera" node-id="camera" position="5 3 0" clear-color="0.925 0.925 0.925 1"
      target="camera-target"
      camera-orbit-control=""
    ></xr-camera>
  </xr-node>
  <xr-node node-id="lights">
    <xr-light type="ambient" color="1 1 1" intensity="1" />
    <xr-light type="directional" rotation="30 230 0" color="1 1 1" intensity="3" cast-shadow/>
    <xr-light
      type="spot" position="-4 1 0" rotation="0 -90 0" color="0 1 0" range="20" intensity="100" inner-cone-angle="20" outer-cone-angle="60"
      anim-keyframe="basic-anim" anim-autoplay="clip:spotlight, speed:2"
    />
</xr-node>
</xr-scene>

• js部分:

component({
  properties: {
    a: number,
  },
  data: {
    loaded: false
  },
  lifetimes: {},
  methods: {
    handleready({detail}) {
      const xrscene = this.scene = detail.value;
      console.log('xr-scene', xrscene);
    },
    handleassetsprogress: function({detail}) {
      console.log('assets progress', detail.value);
    },
    handleassetsloaded: function({detail}) {
      console.log('assets loaded', detail.value);
      this.setdata({loaded: true});
    },
    handleraf: function({detail}) {
      console.log('raf', detail.value);
    }
  }
})

• 动画json部分：

{
  "keyframe": {
    "cube": {
      "0": {
        "position": [-3, 0, 2]
      },
      "50": {
        "rotation": [0, 0, 0],
        "scale": [1, 1, 1]
      },
      "100": {
        "position": [3, 0, 2],
        "rotation": [0, 3.14, 0],
        "scale": [1.4, 1.4, 1.4]
      }
    },
    "sphere": {
      "0": {
        "position": [-3, 0, 0],
        "scale": [0.8, 0.8, 0.8]
      },
      "50": {
        "position": [0, 0.2, 0],
        "scale": [1, 1, 1]
      },
      "100": {
        "position": [3, 0, 0],
        "scale": [0.8, 0.8, 0.8]
      }
    },
    "cylinder": {
      "0": {
        "position": [-3, 0, -2],
        "rotation": [0, 0, 0]
      },
      "50": {
        "rotation": [0, 0, -3.14]
      },
      "100": {
        "position": [3, 0, -2],
        "rotation": [0, 0, 3.14]
      }
    },
    "plane": {
      "0": {
        "material.u_basecolorfactor": [0.48, 0.78, 0.64, 1]
      },
      "50": {
        "material.u_basecolorfactor": [0.368, 0.937, 0.176, 1]
      },
      "100": {
        "material.u_basecolorfactor": [0.176, 0.368, 0.937, 1]
      }
    },
    "spotlight": {
      "0": {
        "position": [-4, 1, -4]
      },
      "25": {
        "position": [-4.3, 0.5, -2]
      },
      "75": {
        "position": [-3, 1.5, 2]
      },
      "100": {
        "position": [-4, 1, 4]
      }
    }
  },
  "animation": {
    "default": {
      "keyframe": "cube",
      "duration": 1,
      "ease": "ease-in-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "sphere": {
      "keyframe": "sphere",
      "duration": 1,
      "ease": "ease-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "cylinder": {
      "keyframe": "cylinder",
      "duration": 1,
      "ease": "ease-in",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "plane": {
      "keyframe": "plane",
      "duration": 4,
      "ease": "linear",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    },
    "spotlight": {
      "keyframe": "spotlight",
      "duration": 2,
      "ease": "ease-in-out",
      "loop": 400000,
      "delay": 1,
      "direction": "both"
    }
  }
}

• 效果展示：