Editing Ray tracing (graphics) (section)

===Ray casting algorithm===
{{Main|Ray casting}}
The idea behind ray casting, the predecessor to recursive ray tracing, is to trace rays from the eye, one per pixel, and find the closest object blocking the path of that ray. Think of an image as a screen-door, with each square in the screen being a pixel. This is then the object the eye sees through that pixel. Using the material properties and the effect of the lights in the scene, this algorithm can determine the [[shading]] of this object. The simplifying assumption is made that if a surface faces a light, the light will reach that surface and not be blocked or in shadow. The shading of the surface is computed using traditional 3-D computer graphics shading models. One important advantage ray casting offered over older [[scanline rendering|scanline algorithms]] was its ability to easily deal with non-planar surfaces and solids, such as [[cone (geometry)|cones]] and [[sphere]]s. If a mathematical surface can be intersected by a ray, it can be rendered using ray casting. Elaborate objects can be created by using [[solid modeling]] techniques and easily rendered.