Each of these shapes can either go on forever (a ray) or stop after a fixed distance (a segment), you can also pick based on a Bounds object.
各种形状都既可以行进到极远处(射线)或停止在固定的距离上(分段),你也可以基于一个边界对象做拣选。
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Especially with the latest techniques in rendering, texture mapping, ray tracing and radiosity, you can make an object look just like it's made of marble or rubber or whatever you wish.