说明：  目前三维的混凝土建模很少见，随机球形骨料在受限空间（球体）随机分布模型,本人自己编写，具有原创性。动画显示建模过程。三种粒径不同的骨料随机分布。模拟混凝土材料的过程。有助于后续有限元计算。
(Random spherical aggregate in the restricted space (sphere) random distribution model, I write it myself, with originality. Animation shows the modeling process. Three kinds of aggregates with different particle sizes are randomly distributed. The process of simulating the concrete material. It is helpful to the subsequent finite element calculation.)