Non-physical light sources

Light sources which can be used in rasterization can also be used in RT. It will be nice to have a correspondence between the rasterizer and the ray-tracer (at least in some rendering mode), the properties of those would need to be uploaded. For instance, those can be: point light, directional light, spot light.

首先比较光栅化器和光线追踪器目前如何表示和上传光照属性。确定受支持的光源类型，以及它们应当对应的渲染模式。完成的标准是：点光源、方向光和聚光灯可以在两条路径中一致地使用，并且光线追踪器可以获得它们所需的属性。

由索引模型根据 Issue 内容生成。