Tutorials

Modelling Theory



Before you get down to modelling for a game it’s a good idea to know some of the theory behind it. The purpose of this tutorial is to supply you with a little insight into the theory behind creating models for in game use.

First let’s go through what is considered one of the most important aspects of making a model for use in a game. The dreaded polygon count.

Before you make a model you must consider a few things first. How big is this model going to be? How often will it be seen and will players be looking at it closely? How often will this model occur in a map? Are there any areas of the model which wont be seen at all?

All these questions factor heavily in the polygon count of a model.

The first example is of a chair. This chair is small, players will only be glancing over it while they shoot at each other and this model will probably occur a number of times in a map.

Here we are looking at a polygon count of maybe 200 to 300 polygons. It’s not very big and is pretty none essential to the map. Players are not going to be looking at it in great detail. Also there will be many of them around the map so they need to be low poly otherwise it will take a lot of resources to cope with the amount of chairs around the place.

About 200-300 polygons is good for anything this size. For instance tables, stool maybe lamps and lighting fixtures.

Next we look at intermediate sized models. For instance, a radar dish. It’s not massive and it will occur less often then a chair. But it will occur a few times maybe 3 to 5. Here we are looking for a polygon count of around 700 you can maybe afford to jump a little above that maybe even to 900 if it’s a high detailed model.

We then have large models. The example for this is a satellite dish. Imagine you are making a map for CS:S and the objective is for the terrorists to bomb a large satellite dish. This means that there will be one of these dishes in the map and it will also be quite central to the map. Player will be looking at this quite often and maybe in detail (providing someone isn’t camping the bomb zone with the AWP of course.) You can afford to go for a quite large poly-count. I would choose about 1500 polygons again you can maybe justify 2000 if it’s a really gorgeous model. I can see some situations where this is justification for a 4000 polygon model to be used in this sort of situation but that’s really for single player maps in my opinion or maybe if you have made a really colossal structure.

Now in this large model there might not be parts players will not see at all or will only see from a distance. You can afford to make shapes with less sides in these areas and even delete whole polygons if the player wont see them at all. This is called polygon culling.

Weapon models are a bit tricky. HL2 you are looking at counts up to 3500 sometimes. But remember that includes the polycount for the hands. I try to stay under the 3000 mark. You can do a lot with about 2500 polys. Hand guns and melee weapons can get away with 1000 polys. If you find your self with a weapon like a baseball bat and you have modelled it with about say 500 polys. Ok go add some more details to it. In the long run it will make your model look really nice.

So ask yourself. “What am I modelling?” “Why am I modelling it?” “Which category does it fit into?”

Ok now lets have a quick glance through all these “maps” we hear about.

Texture maps:

This basically adds the colour and pattern. You need this first. You want a green dog? You make a green fur texture. You want rusted metal? You make a rusted metal texture.

Here is a simple rock texture not much but you get the picture.

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Bump maps:

I love these. Basically a bump map is a black and white map which when applied to a model simulates 3d detail. It tricks the game engine to render things as if they had these details or “bumps” in them. In a bump map black is the lowest point and appears as though the model is depressed and white is the highest point and appears as though the model is raised. How ever be careful not make a bump map contrast too much or it will look like it has too much depth and becomes obvious that the detail is not real when you look at it from certain angles. Remember bump maps don’t actually affect the model it’s just trickery.

This is a bump map for the rock texture shown above. you can see the lighter areas show where the rock is highest.

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Specularity maps:

Again a black and white map. This determines how highlights are displayed on the model. When you have been walking through HL2 and you see the beautiful effects of the lighting reflecting off the floor. This is a Specularity map. To my understanding white areas let all light reflect making a highlight and black does not let any light reflect. And if i see any more people calling this a normal map i will be slapping them.

Ok so you don't really get sparkly rocks but for the sake of this tutorial we do. You can see it's not very different from the bump map however varying from texture to texture you may wish to make a specularity map independently of the texture rather then building from the texture as I have done.

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Normal maps:

Ok I’m still learning these so I’m almost as clueless as you. I do know the theory behind them somewhat so I’ll have a go. It works in a similar way to bump maps in that it makes detail look like it’s there when in fact it is not. How it works is. You first create a really high detailed model. And I mean in the millions of polys here. No texture maps or anything you model every detail you want. Then create a map from this (don’t ask me how I’m still learning) and you project it onto a low polygon mesh. Remember when playing doom 3 you could see the 6 packs of topless zombies, they weren’t modelled there they are normal maps.

You won’t apply all these maps to each model. Small static props for instance will only use a texture map.

I will cover more theory behind creating models for games as I write the upcoming tutorials. This is just really a quick overview if anything and can be used as reference.

If you have any questions email me at simon.ashbery@ntlworld.comalso for more info have a look here ftp://ftp.futurenet.co.uk/pub/arts/Glossary.pdfit’s more for creating models for use in renders or animation but has some good stuff which applies to game modelling as well. Look forward for my new modelling, UVW mapping, texturing and compiling tutorials in the future (god I do make work for my self don’t I?)

Athlete{UK}

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