Game Project part 1: Do you think it’s going terrain today?

Last time I talked about the new game project I’m planning to start. I was feeling quite enthusiastic about it and I had a bit of time while I was away in the caravan, so I decided it was time to actually start doing stuff on it!

I won’t say too much about the actual concept of the game yet, and in fact it might still change a bit before it’s finished, but it’s going to be set in a 3D town that you can wander round. So one of the first things to do will be to get the bare bones of a game engine running that can display the 3D world using WebGL, and also get an editing pipeline working so that I can create and edit the environment.

For most of the 3D editing I’m planning to use Blender. It’s free, it’s very powerful, it has a great community, it runs on almost everything and I already know how to use it, so what’s not to like? At some point I might want a more customised editing experience, maybe either writing a plugin or two for Blender or adding an editing mode to the game engine itself, but for the moment vanilla Blender will do.

The first element of the environment that I’m going to focus on is the actual ground, since it’s (literally) the foundation on which everything else will be built. I could model the ground as a standard 3D mesh, but it would be more efficient to treat it as a special case: it’s basically a single plane but with variations in height and texture across it, so we can store it as a 2D array of height values, plus another 2D array of material indices. My plan for the ground was as follows:

  • Add the ground as a “grid” object in Blender, and model the height variations using Blender’s extensive array of modelling tools
  • Export the geometry in OBJ format (a nice simple format for doing further conversions on)
  • Write a converter program in C++ to convert the OBJ file into a compact binary format containing the height values for each point and the material values for each square
  • Create a single texture image containing tiled textures for all the materials used
  • Write JavaScript code to parse the binary file and actually display the terrain!

(We could load and parse the OBJ file directly in JavaScript, but this would be significantly larger, and size matters when working in a browser environment, because every data file has to be downloaded over the internet when running the game).

Editing terrain in Blender

The terrain work went reasonably smoothly once I got started. Editing the heights as a Blender grid worked well, with the proportional editing tool being very useful. Writing the C++ converter tool didn’t take too long, and the binary terrain files it creates are about 10 times smaller than the original OBJ files exported from Blender, so it’s well worth doing the conversion.

Terrain rendered in WebGL

Writing a WebGL renderer for the terrain was a bit more involved. The main problem I ran into was an unexpected one: I could see dark lines appearing along the edges of the terrain “tiles” when they should have joined up with each other seamlessly. I eventually traced this to my decision to store all of the textures for the ground in a single image. This works fine for the most part, but I hadn’t foreseen that it would cause problems with the filtering used by WebGL to make the textures look smoother at different scales. This causes a slight blurring effect and when you have multiple textures side-by-side in a single image, it causes their edges to “bleed” into each other slightly.

I solved this by putting 4 copies of each texture into the image, in a 2×2 layout, and mapping the centre section onto the terrain, so that the blurred edges are never used. This reduces the amount of texture data that can be stored in a single image, but it’s still better than storing each texture in a separate image and having to waste time switching between them when rendering.

Now that it’s done I’m reasonably happy with how it looks. I was a bit worried that the height differences might distort the textures too much, but they actually don’t seem to. I do plan to add some additional texture images for variety, and it should also look a lot better once some of the other elements of the scene (buildings, roads, vegetation, etc.) are in place.

Another shot of the rendered terrain

The WebGL renderer is still in its very early stages; right now all it can do is render a single 3D terrain object with a plain sky blue background, illuminated by a single directional light source, and allow me to move the camera around for testing. Obviously it’ll need a lot of other stuff added to enable it to show everything else required for the game, as well as to make things look a bit nicer and run a bit faster – but we’ll get onto that next time.

(Incidentally, the texture images are all from textures.com, a great resource for anyone doing anything 3D related. You can get loads of textures of all sorts from there and they’re free to use for most purposes).

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