Within a side, the color stays the same because of the light's parallel rays.

每面内的颜色都相同，这是因为光线是平行的。

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This paper presents a new method of drawing perspective shade and shadow in parallel rays, which makes use of plane trace and geometrical drawing method.

探讨了一种利用平面迹线和几何作图法，作无灭光线下透视阴影的新方法。

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The method comprises the following steps: after parallel rays project to a target surface area element, acquiring a path parameter of each ray from incidence to reflection;

所述方法包括：当平行射线投向目标面元后，获取每条射线从入 射到反射的路径参数；

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Instead of converging to a point on a focal plane behind the lens, the rays spread out so as to run in a thick stream roughly parallel to each other (see chart).

ECONOMIST: MONITOR