The traceable light should be clean, it should not be muddy. The designer has reconsidered the property of light, light is a kind of wave, should choose the simple pure light wave. Projection lamp can make the shadow clear and pure in the space, the boundary is clear. What the designer needs is this kind of true expression, in which the viewer sees the object as it is, and is not disturbed or influenced by various other factors, including the influence from light. As the diamond sutra said in the should do so view.