What is physics based rendering?
A new feature we will be adding to the Elemental engine this Summer will be physics based rendering or PBR. At the beginning of the project we talked about not only using the project to help people in understanding more about Taoist principles, but being true to form in using these same Taoist principles in the development of the engine, the workflow, in fact in every aspect of the project as far as humanly possible. Interestingly PBR is one of the things which came out of the box with one of the most important and misunderstood aspects of Lee style Tai Chi already at the top of the agenda: light.
Looking out of my window I can see the sky, and I know the light that illuminates our world ultimately comes from the sun, with a little help from the stars. There are different theories about exactly what light is, is it a particle or a wave? What is of interest for us as artists working on a 3d environment is realism, in fact we aim for photorealism, and in order to achieve this takes an enormous amount of work. What PBR offers is is a way for the engine itself to handle light in a more realistic way. To understand this and how it can be achieved we need to consider what happens to the light we see between leaving the sun, and when it enters our eyes. A simple understanding is that light leaves the sun, reflects from objects in our environment and then enters our eyes where it is processed in such a way our minds can perceive those objects. However if we treat light in this simplistic way in a game engine we get cartoony looking results. Something is missing.
First of all the direct light from the sun is not the only way in which objects are illuminated, light also enters the atmosphere and is scattered in such a way that the blue light predominates. This is what produces what we might call ambient light or background lighting, and our current engine has this otherwise all shadows would look completely black. However there is more to it than this, because light interacts with every object it encounters, and a portion of it is reflected, and some of it is absorbed by the object. Different objects have various characteristics so that some reflect all the light that hits them, but some objects are transparent and they retransmit some of the light that enters them, and the light is changed when it comes out of that object. So light is reflected, and it takes on some of the quality of light that reflects it, think of a red ball on a white background, some of the light reflected from the ball will make the background look a bit red, this is called radiosity. Of course when we look at objects in the world we generally speaking dont think about how they affect the light, but subconsciously we tend to recognise how natural light looks in a natural environment. Think of it this way, light bounces around on it’s way to our eyes, and picks up some of the characteristics of the objects it encounters. So when we look at an object we expect to see that it is partly coloured by the environment around it.
