Please pay attention to the subtle differences, particularly the Tangential line marking the fillet's point of contact with its adjacent surface, and how the reflections break there as well.
请注意细微的差别，尤其是切线标示出的倒圆角与临近面的连接处，还有在那里反射光是如何被打断的。
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Top: Checkpoint Charlie crossing point, in June 1968, then marking the border between East (Soviet sector) and West Berlin (American sector).