From the course: V-Ray Next: Unreal Engine Rendering

Light behavior basics

From the course: V-Ray Next: Unreal Engine Rendering

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Light behavior basics

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- [Instructor] Before moving on to the final topic for our lighting chapter, which is Global Illumination, I thought that it would maybe be good for the benefit of those who are new to lighting and rendering in a computer graphics application, to just cover a quick breakdown of the basic workings of both Global Illumination and so in turn, light itself. With an understanding of what GIR and direct illumination is, probably best coming by contrasting it to its CG lighting opposite. Which is local or direct illumination. If we go ahead and take a render of our GI start scene then, through the bottom of the stairs camera. Direct illumination is exactly what we are seeing here, because by virtue of how a CG lighting system works, adding lights to a scene and then rendering without a GI engine enabled can only ever give us direct illumination. A system in which only surfaces that are in direct line of sight to a light object can receive illumination. This computer graphics approach to lighting is not of course how light behaves in the real world. The basic process of which on planet Earth being that once light is emitted from a source, it will then travel through the environment until it strikes the surface of an object. At this point, a lighting phenomenon known as inter surface reflection will occur, which simply means that a portion of the light energy hitting the surface will now be reflected or bounced. Now dependent upon the amount of energy coming from that initial source, the light should be able to bounce off quite a number of surfaces, with each bounce losing a little bit of energy, and each bounce picking up a little bit of coloration that will be inherited from the surfaces that it has interacted with so far. The end result of all this bouncing being that the surrounding environment will become lit with even the darkest nooks and crannies of a space ending up receiving at least some level of light, even though they may be far away from the actual direct light sources. The recreation of this complex process by a Global Illumination engine is what ultimately gives us the ability to create CG lighting scenarios that have very high levels of accuracy and realism applied to them. And so with that basic explanation of GI and thus light behavior under our build, we're ready to move on to the final exercise for this chapter, and take a look at using V-Ray's GI rendering tools.

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