如我上面所講, CAD Object唔等於全部都係NURBS object
以parasolid做kernal嘅software計, 一個望落係cube嘅嘢可以係
1. 一個analytic solid object, based on parametric feature
2. 一個surface object, with 6 faces (i.e. hollow cube with 0 thickness)
3. 六個貼著擺埋一齊嘅surface objects
第1個case佢其實唔係一個NURBS嚟, 有啲人叫佢做analytic object
佢類似一個primitives咁樣, 係通過parameters定義出嚟嘅, 唔係通過combination of splines
第2同第3其實都可以唔係NURBS嚟, 因為佢係plane surfaces嚟架嘛
如果你真係要做到exactly有齊你上面3條紅線做邊界嘅話, 應該就真係要3個object
不過我真係唔識blender, 我係以自己對mesh嘅理解推斷