Eli5: How does cgi go from a grey ball to something hyper realistic
In: Technology
The “grey ball” is the model. They make polygon models of everything, and they can make them move in realistic looking animation. A ball is really simple, most models are much more complex, made out of millions of triangles. Really small triangle “polygons”
Once they have their model. They dress it all around in “textures” this is flat artwork that wraps all around the model, making it look real. Instead of a grey ball model, they put a texture on it to make it look like a realistic basketball, orange with the stitching, etc… or they put color on the clothing, they put green on the grass, etc.
Nowadays, they use “photogrammetry” where they take high resolution photos of real life objects and use that to make the artwork textures, super realistic looking. Slap that on a realistic model polygon and you got something great going!
Next is about lighting and effects. This does way more to make the game look realistic than most people realize. If you fuck up the lighting, the best poly and textures in the world will look fake.
Finally, you handle the animations/motion to look real. Tie it all together, render it, and you get insanely good looking CGI.
Animations are underrated. Some games like Ubisoft games have great graphics and lighting, only to have robotic animations and stiff lifeless characters so it looks terribly fake. And BORING! Meanwhile, Rockstar games does maybe the best in the industry for animations and it makes their games so immersive and lifelike. It’s extremely hard work to get animations right which is why Ubisoft and others just dont invest in it and let their games be boring and robotic
If you’re starting from a grey ball you’re probably using virtual sculpting tools, and those are made to work in the same way that clay sculpting works. So the answer is the same as how you’d make a realistic clay sculpture.
You don’t need to do it that way of course, if you’re modeling something like a car you might do something more like cad where you define various straight lines and curves then fill them in to make the 3D object.
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.
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