Artificial Intelligence?


What happened to week eight?? It was definitely there, but I must be getting lazy at making progress flowers.

This week my focus is on the little interactive bits that make videogames what they are, which includes working on menus and non-playable characters (NPCs). As part of my feedback from last week I was told to not move on to create a new level without finishing this one, and while most of the graphical elements are in place, its lacking occupants and and a real start to the game. The little photo above shows the little progress I’ve made with the new level over the weekend, although it’s much easier to draw on tracing paper in good light so I’m going to have to start putting some day-time into drawing it.


Today I began work on the first character that the player can interact with, the Maneki Neko. Ultimately, I’d like the game to begin with a short cutscene and the cat awakening Hana in a foggy dream-like state, and this may even be possible now that I have some extra animations. My plan is to look at the Spelunky source code to work out how the opening cutscene has been programmed, as I’ve had some problems working Game Maker around cutscenes in the past.

My first task was to create a walk-cycle animation for the cat, which somehow proved much easier than animating only two legs! I kept the leg length to a constant 2 pixels and tried to use as few frames as possible, as this animation won’t actually be seen much in the game at all. I used this video for reference, although only picked out the more “essential” frames.


The human walk cycle I developed uses eight frames, four for each leg forward. I ended up only using four for the cat, as it easily gives the illusion of having either foot in front of the other!


The tricky part was getting the cat to walk on his own, without player input. The game’s main character relies on the intelligence of the player to not walk into walls and avoid obstacles, but the cat would have to rely on a set of calculations in order to move around. There are several ways you can achieve this in game maker, but several that became unavailable to me because of the nature of the movement.

I wanted the cat to constantly pace from left to right, turning back on contact with a wall. I also wanted its behaviour to change when in close proximity to the player, so that it follows the player briefly. Luckily, I found an example that someone had already made that has a similar thing- except that the pacing objects are enemies which move to attack when in proximity with the player! You can have a quick look at that here. Based on the code from this example combined with the movement mechanics which came with the grandma engine, I came up with this little bit which makes the cat pace while the player is far away:


This basically sets up a timer which which turns the cat around after a certain period of time. The “counter” moves up in intervals of .25 until it has reached 60- in this time the cat will move left. After from 60 until 120 the cat will move to the right, and at 120 the counter restarts from 0. This is only while !can_see, which is while the cat “cannot see” the player.

While the cat can see the player, I’ve simply set a constant speed in the direction of the player. This speed is faster than its previous pacing speed, but not as fast as the speed of the player. As long as the player is moving, the cat will never catch up!


There are a few more lines to prevent the cat from walking through walls and an image_xscale code which turns the image around when walking left. Otherwise, this code is the cat’s brain. It’s not perfect- for example, if the player stops then the cat will just continue to walk past until it begins pacing again. I don’t think this is much of an issue for an object that only appears in the first room of the game!

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