Game Project part 4: Vegetation… that’s what you need

Oops. I didn’t mean to leave it quite so long after part 3 before posting this. I have been doing quite a lot on the game, it’s just either been dull (but necessary) rearranging of the code that I’m not going to bother writing about, or it’s been other coding stuff that I’ll discuss in part 5 (my coding has got a bit out of sync with my posts on here).

Having now got the basics of human models and animation working using WebGL, for the next several posts I’ll be shifting my attention back to creating the game world, and building the tools I need to give the characters a more interesting environment to explore. Starting, in this post, with trees!

As luck would have it, I already had a very useful chunk of tree-related code that I wrote for the Botanic Gardens Station model I made a couple of years ago, and I was able to integrate that code mostly unchanged into my new game engine, allowing me to place trees into the game world. But although the main core of the tree generation code was already there, I wanted to add three major things for this game:

  1. A nice tree editor. I always intended to make one for the Botanics project, but in the end I only used one type of tree for that model, so I did it by just editing numbers in the code until I got it to look vaguely like I wanted it to. For the game I want a more powerful way of editing tree types.
  2. An easy way of placing trees into the game world. I want the ability to place individual trees at specific points, but I also want to be able to generate areas of woodland without having to manually specify the exact location of every single tree. I already had something like this for the Botanics model which I could adapt.
  3. A way to keep the game running fast even with lots of trees in the world. The tree models contain quite a lot of polygons and on less powerful systems (like the Macbook Air that I’m using for much of the game development) things can easily slow down to a crawl when there are lots of trees visible. I need to speed up the code so that it can cope better with this.

Altogether that added up to quite a lot of work, so much so that I’m going to split off the third item into a separate blog post about optimisation and just concentrate on 1 and 2 here.

No. 1: The Larch. The Larch *

I wrote most of the tree editor on the train down to London. All the people standing in the aisles who would have been on the previous train if it hadn’t been cancelled made it a bit hard to concentrate, but luckily this code didn’t require too much thought – it was mostly a case of adding edit controls to a web page and writing code to move values to and from them. The resulting editor isn’t particularly advanced or pretty, but it works and will be far better than trying to create tree types by editing numbers in the code like I was before.

It’s a bit like a very primitive MakeHuman for trees, in the sense that it lets you edit tree models by tweaking meaningful(ish) parameters like the lengths of the branches, the density of the leaves and the overall shape rather than having to worry about the individual vertices and faces like you would in traditional 3D editing. Once I’m done editing each tree, I can copy the text below the tree graphic and paste it into my JavaScript code to include that tree type in the game.

Placing trees using Blender

One downside to generating geometry such as trees within my code is that it means I can’t easily use a 3D editor like Blender to put them in the scene – if I was to model a tree using Blender and put it in my scene and export it, I’d have a full 3D mesh, which isn’t what I want, because I want to generate the meshes for the trees within my JavaScript code instead.

However, I still want to use Blender to build the game scenes. I’m already using it for my terrain, and it has lots of amazing editing tools that will be handy for future parts of the game. I could just leave the trees out of the Blender scenes and put them in some other way (either by building some editing tool of my own or just by tweaking the co-ordinates manually), but that would be more work, and I’d have to remember that there were going to be trees in certain places when editing the other stuff in Blender, so it’s not ideal.

“That’s not a cube, it’s a tree”. “Oh. I see you’ve played Cubey-Treey before!”

Instead I’m just putting placeholder objects in the Blender scene (I’m using cubes but they could be anything), and giving them names that make it obvious they’re meant to be trees, and also include their types. Then I’ve extended the terrain converter program that I wrote way back in post 1 to recognise the placeholders and spit out a list of their positions and types in a form that I can easily incorporate into the game code. That way I can move the trees around and change their types from within Blender like I wanted, but I still get the advantages that come with generating the tree models within my game engine.

But what about whole areas of woodland? As I said earlier on, I didn’t want to have to tediously place every tree manually for those. Once again I’m using the idea of a “placeholder” object in the Blender scene. This time it’s merely a base that trees will later sprout from. The code I wrote for the Botanic Gardens Station model can automatically place trees on this base according to some parameters. I can tell it what types of tree I want in this woodland, how densely they cover the ground, how close they’re allowed to be to each other, etc. and it will generate a woodland for me with very little effort on my part!

My terrain model in Blender. That yellow rectangle is an area that I’m marking out to become a woodland.

Of course, there’s always a risk that I won’t like what it comes up with. If so, I can change a “seed” number and it will place the trees differently, though still obeying the same constraints as before.

Back in the game engine, my character can now go for a walk in the woods.

So now the game has a slightly more interesting landscape! There are still many more elements to be added of course, but my next task is going to be to speed it up. It’s already slowing my laptops down noticeably when I add a woodland to the scene (though my nice big Linux desktop PC with proper graphics card doesn’t even break a sweat), so that needs to be addressed before I go too much further.

* may not actually be a larch

One thought on “Game Project part 4: Vegetation… that’s what you need

  1. Pingback: Game Project part 5: Billboards, Culling and Depth Cuing: not just a load of random words… | GCat's World of Stuff

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