帮助D3D学习者了解向量与矩阵运算。 实现效果：指定世界空间中的任意位置作为原点，指定任意长度作为旋转半径，立方体围绕圆心旋转。-D3D assist learners know vector and matrix operations. Achieve results: the designated space in the world at any position as a starting point, designated as the rotation radius of arb