I'm a software engineer who works on game development part time. I teach game development (on gamedev.stackexchange.com and lynda.com). I'm always working on something, and I'll post updates here. Let me know if there's a game development topic you want to know more about, I probably know the answer, or at least where to get one.

Saturday, August 27, 2011

Progress Update

I’ve been spending my time on two areas lately: the engine and unit tasks. 
The engine:
Vertex/fragment shaders mostly. These have helped a lot. Primarily with the slice feature. Age of Goblins does chunking with its terrain. Before the shader, these chunks were 64x1x64. Each chunk was 1 cube tall. That made it really easy to “slice” through them. I’d just not draw chunks above the “slice level”. Additionally I have some code that creates what I call “void caps”. This is a special layer that hides all the cubes the player hasn’t discovered yet, as well as the void that’s left when you start cutting through geometry. Of course this came at a performance cost. I needed considerably more chunks to fill the same volume when they’re only 1 cube tall.
Now the shader comes along. With a little bit of GLSL code in the fragment shader:
if(WorldPos.y > maxY)
I can get rid of all the geometry above a specific height. Now I can use whatever chunk height I want! This sped things up quite a bit. Luckily I’ve kept all my code nice enough that I only had to change the y chunk size constant and everything still works. 
Elsewhere in shader land I’ve been tinkering with some lighting effects that should give the landscape a bit more depth. A sort of “lighting rig”. Still needs some more tweaking and testing with different conditions. Finally, I’m in the middle of working out how I’m going to do some vertex displacement to recreate the smoother cubes on the graphics card (as seen here).

Unit tasks:
Building off my previous work of giving units a main goal and sub goals. I’ve implemented a goal stack. This allows me to give units higher level goals, and not have to walk them through each little task along the way. The goal stack works something like this:
    CurrentGoal = CurrentGoal.GetSecondaryGoal()
In the end, you’re left with a list of tasks, in order, that need to get done before the main goal can be started. To put this into an in game example, the situation could be that I’ve just ordered a goblin to place a rock cube at position xyz. The goblin doesn’t have a cube like that in their backpack, but there is one in a storage bin near by. So before the goblin even moves their goal stack would look like this:
  1. Go to storage bin     <— top of stack
  2. Pickup rock cube
  3. Go to position xyz
  4. Place rock cube
Clearly there’s some more work in creating that list, like finding the nearest available rock cube. But that’s all taken care of by the goblin as well (with a little help from the world item finder).
Pretty neat! To help test this out I implemented in-world objects. So when goblins are clearing away cubes, once their backpacks are full, they’ll just leave the cube (in item form) on the ground. This is similar to Dwarf Fortress (sans the backpacks) and Minecraft (much larger backpacks). Of course (as usual) the in game representation of this is just a little colored dash, since I haven’t gotten around to implementing the pretty graphics for it :). 

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