How Objects are Created for Video Games

Step 1: Creating a base model.

In this case, I was making a barrel. Before you can move on to the fun stuff, you have to create a simple model to work with! There are a lot of 3d modelling applications to choose from (Blender, 3ds Max, and Maya are three well-known ones), but I used Maya. At this stage, it's important to make sure that the model's topology is good - that means making sure to only use quadrilaterals and to try to keep them as close to similarly-sized squares as possible.

Step 2: Subdivision and sculpting.

Next the model is brought into a 3d sculpting application, like Mudbox or ZBrush (I used ZBrush for this), and subdivided into millions of polygons so that you can sculpt finer details into it. This is why it's important to have good topology in the original model: if you don't, you'll end up with strange aberrations.

After the object is sculpted, the high-resolution version is exported to be used later on - you'll see why momentarily.

Step 3: Retopologizing the model.

Now we need to turn that 1,000,000+ polygon model into something that a game engine can use! To do that, we'll create an object very similar to the one in step 1. The reason we don't use the original model as the final version is that we're trying to minimize the number of polygons needed to accurately capture the form of the object - take a look at the top of the two models to see how the topology is different.

Step 4: UV mapping.

If we want to add textures to the object (and we definitely do), we'll need to do something called 'UV mapping'. Basically, we take the polygons of the barrel, peel 'em apart, and lay them out like a bear pelt (or should I say a barrel pelt, amirite). Then we can overlay an image on the 2d layout and the game engine will be able to render it all.

It seems odd that I haven't used the entire image to lay out barrel's UVs, right? That's because we're creating a thing called a texture atlas. It'll make sense by the end of this post.

We're now ready to export the low-resolution model. This will be the final version that gets used by the game engine.

Step 6: Baking maps.

You know that high resolution, sculpted model we exported earlier? This is where it comes back into play. I use a program called xNormal to bake maps from the high-res model (in other words, to take the details from that high-res model and convert them into a 2d image that can be applied to the low-res object).

I won't bore you with all the details, but again: I highly recommend reading up on normal mapping and ambient occlusion if you're interested.

Here's the final texture map! Specifically, it's an ambient occlusion map (basically a shadow map) and a wood texture. You can see that there are multiple objects in the same map (although it's not finished yet) - that's the texture atlas I mentioned earlier. Having multiple objects' textures in the same map allows the game engine to render scenes much, much faster.

And here's the second piece of the puzzle: the normal map. Normal mapping lets the game engine realistically fake how lighting affects little details - things like indentations, scratches, and warped surfaces.

Step 7: Putting it all together.

And there you have it! The final model with texture and normal maps applied in Unity. The scene is from a game I've been working on for a while, but it's nowhere near finished (which is why the background is incomplete).

If you guys have any questions about the process (or would like similar posts on related topics), lemme know in the comments.

If you're interested in modelling and/or game development, take note of the following:

- Unity is a very versatile, powerful, and easy to learn engine that's free to use for personal projects and some commercial endeavours: https://unity3d.com
- Blender is a free, open-source piece of animation software with a solid body of tutorials and how-tos: https://www.blender.org
- Autodesk Maya (which is what I use) has a free student version with all the features of the commercial version. Check it out: http://www.autodesk.com/products/maya
- Autodesk Mudbox is a 3d sculpting program. Like Maya, it has a free student version available: http://www.autodesk.com/products/mudbox/overview
- xNormal is phenomenal for baking all kinds of maps - textures, ambient occlusion, normals, height maps, you name it. Also, it's free! http://www.xnormal.net