three.js CustomBlendingEquation
这个常量可以用于所有的材质类型。首先将材质的混合模式设置为THREE.CustomBlending，然后设置所需要的混合方程、源因子和目标因子。
代码示例
const material = new THREE.MeshBasicMaterial( {color: 0x00ff00} );
material.blending = THREE.CustomBlending;
material.blendEquation = THREE.AddEquation; //default
material.blendSrc = THREE.SrcAlphaFactor; //default
material.blendDst = THREE.OneMinusSrcAlphaFactor; //default例子
混合方程
THREE.AddEquation
THREE.SubtractEquation
THREE.ReverseSubtractEquation
THREE.MinEquation
THREE.MaxEquation源因子
THREE.ZeroFactor
THREE.OneFactor
THREE.SrcColorFactor
THREE.OneMinusSrcColorFactor
THREE.SrcAlphaFactor
THREE.OneMinusSrcAlphaFactor
THREE.DstAlphaFactor
THREE.OneMinusDstAlphaFactor
THREE.DstColorFactor
THREE.OneMinusDstColorFactor
THREE.SrcAlphaSaturateFactor目标因子
所有的源因子的值，在目标因子中都是有效的。除了：
THREE.SrcAlphaSaturateFactor