Modelling and representing scenery

Member
Posts: 260
Joined: 2005.05
Post: #1
When making a terrain, as mentioned by a neighbor thread, you usually use a big 2D grid with height values. That makes lots of sense. Looking up a height value for a specific x,z point is easy, frustum culling is easy etc.

But what I don't like is that it gets a bit square. If I want to put a road through the scene, with sharp edges, this is not trivial. The edges get blurry or choppy. And what about houses? I don't want the house look like it is stuck down into the terrain, I want it to fit a bit better, if I can.

When modelling something like a city environment, what approach would you suggest? Not only modelling tools (although they are important), but also the internal representation. All game books speak about terrains, but how about a mixed situation when the cartesian grid becomes a problem?
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Luminary
Posts: 5,143
Joined: 2002.04
Post: #2
I found with Outnumbered that it wasn't problematic to treat the scenery as one big static mesh. I ended up using a 3D hash space for collision detection, but if you have enough that you need to do effective culling, you might want to use a quadtree for rendering as well.
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Moderator
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Post: #3
For building placement I can think of four things in order of difficulty:

- Most obviously the building can be placed to more naturally fit the height map and the height map can be adjusted to more naturally fit the building.

- A free-form mesh can be added underneath the building to blend better into the surrounding terrain.

- You could automatically have the height-map adjust itself to `stick' to the bottom of the building.

- You can `cut out' a section of the height map and `stitch' in a free-form mesh in its place which fits the building. You could do the same for an entire area like a city within the greater heigh-mapped world I suppose.

In many games that I've seen they might add a free-form object like a platform (possibly a big concrete pad) where they are going to put a building(s) and streets. Sometimes the terrain is simply flattened for the streets.
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Posts: 260
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Post: #4
Flattening terrains for streets is common, yes, like in Black&White and 4x4. For simple paths in a natural surrounding, that works well, but less so in a city environment. I am thinking about using a free-form mesh for the whole map, but maybe that is to complicate things too much. It seems it depends a bit on how much natural scenery and how much city-style environment I want.

Does everybody make their own scene editors?
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Post: #5
> I am thinking about using a free-form mesh for the whole map...

I am too. Until now I've been using height maps, but the advantages of free-form mesh are appealing -- especially since I've just started playing with using Newton for collision and physics. Collision detection with height maps is real easy, so that was one reason among many that I was using them. But now with Newton, do I really care about that anymore?

Also, I believe Halo's outdoor environments are free-form mesh, but don't quote me on that.

> Does everybody make their own scene editors?

Not always. For instance, if you have Maya you can script it to do your bidding there, depending on what you want. One of the cool features available with it is a `blind data' object which allows you to attach your own custom data values to basically anything in the scene, from entire objects down to individual mesh faces. Using its built-in scripting language, called MEL, you can create your own interface elements for Maya, like dialog boxes with sliders and buttons, which you can use to assign that data. The possibilities are endless within Maya... Of course, it depends on how much time and effort you can invest in learning how to work with MEL.

And speaking to both of these topics, I was just looking at the Making of Oblivion documentary yesterday and I payed particular attention to how they put together their cave environments. I don't have the PC version so I was unaware of how their scene editor worked. It's not ground-breaking or anything, but what they do is make individual sections of the caves and tunnels as free-form meshes which can be reused, and they snap them together in a grid system however desired. I imagine that the way they do it could be useful for outdoor environments as well -- on a snap-together grid system I mean. They said they do that so the sections align seemlessly. In my mind, I'm thinking that would help simplify culling as well.
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