Global Illumination using Photon Maps

Caustic (optics): In optics, a caustic or caustic network is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface.  The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light. Therefore, in the adjacent image, the caustics can be the patches of light or their bright edges. These shapes often have cusp singularities.
“焦散”是指当光线穿过一个透明物体时,由于对象表面的不平整,使得光线折射并没有平行发生,出现漫折射,投影表面出现光子分散。
比如,一束光照射一个透明的玻璃球,由于球体的表面是弧形的,那么在球体后的投影表面上就会出现光线明暗偏移,这就是“焦散”。焦散的强度与对象的透明度和对象与投影表面的距离、光线本身的强度有关。
焦散是三维软件中的一个名词,它主要在后期渲染的时候,才会被提及。它的主要作用就是产生水波纹的光影效果,为了达到真实的效果,它可以计算很精致、准确的光影。但是好的效果,都是要付出渲染时间的,它的渲染是很费时间的。


Specular reflection 单向/镜面反射

photon mapping

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