Eli5: How does cgi go from a grey ball to something hyper realistic
In: Technology
There are three major components to any digitally rendered image. The first is the model, which is the 3D shape created by polygons on the computer. That’s the “grey ball” you’re referring to. The more polygons the model has, the more detailed it is, but also more complex to make and resource intensive to create and render for the computer. Consider old school 3D video game graphics to get an idea of what a low polygon model looks like, instead of curves, it has a lot of edges and it looks crude. When you have more polygons, you can create curves and complex shapes without losing fidelity.
The second component is the texturing, which is the “paint” so to speak that you put on the grey ball to make it not grey. It can be anything, from hand painted textures to simply overlaying actual photographs on the model. It’s the “skin” of the model and what gives it its color and features.
Lastly, there’s the shaders. The shaders are essentially the software that create the artificial light that lights the object, and calculates the direction of the light source, how the light interacts with the object and the shadows it may create. Good shaders will take into account the shape and contours of the model as well as the material it’s made out of. Take for example a basketball. It has thousands of tiny bumps on it and ridges, which a good shader would take into account and have each of them cast the appropriate shadows as well as make the light disperse on the object accordingly. Things like whether an object is reflective or glossy or matte or whether it allows light to go through or not need to be taken into account.
Contrary to what many people think, out of those three the most important one to make a model look realistic is not the textures or model but rather the shaders. You can have low fidelity models with simplistic textures look real with the right shader. Even if we don’t realise it we’re quite good at recognising whether something is real or not because, well, we see things with our eyes every day. And seeing is simply getting light reflected off of objects into our eyes. Intuitively we know how things are supposed to look like and how light is supposed to interact with them. So when artificial lighting is done well enough to appear natural, it can make any object look real in turn. However getting realistic lighting in CGI is very complex and resource intensive, which is why it’s usually the one of the three getting the short end of the stick, and why ultimately a lot of CGI sticks out as looking fake.
Latest Answers