This last weekend I finally got around to adding parallax in the vertical axis. It’s something that I’d just never gotten around to doing, and all that was needed was an additional 4 or 6 lines of code.

How is that relevant to G2DP? Because I’m using the Generic 2D Platformer game library in Beer Bottle Rocket Man. As I use it, I see areas that could use improvement. And areas that are potentially broken and need some work done.

So tonight I’ve added a drawEntity method to the Camera class, which allows easy drawing of any entity, in addition to the player, so the developer no longer has to track the screen position of said entity. I had it in place for the player for a long time, but tonight it just made sense to add that functionality.

The numbers, 0 through 3, represent the four different corners of a tile (as shown in the image). The combinations of corner manipulation with 100% transparency are indicated in the image.

Here we have the hero inside a “secret area”. It’s not so secret if you’ve been testing out the demo on a regular basis. It’s the first room of the demo, just with a big rock placed onto the foreground layer.

Now the player can see where the hero is at when he’s standing behind a tile.

If you’d run the previous demo, you would have noticed that whenever you pressed jump, the hero would jump as high as he could, every time, no matter whether or not you held the jump key or simply tapped it. I’ve fixed that, so a tap results in a slight hop.

Edit: I finally found the link to the article that this effect is based on.

The following picture does not do it justice, but it shows off 4 images, layered accordingly.

I had this little problem lurking around at the back of my mind. I wanted a simple way of specifying where our hero starts in the level. Up to now I had just been dropping him in the top left of the level (position 10,10).

Not any more. I’m using the Tiled editor’s “group” layer, as you can see.

There’s that “ACTORGROUP” layer, that holds the location of the Hero, and later on will tell G2DP where to create the NPCs. Notice the little orange box labelled “Player”.

That gives us easy hero placement.

I have decided that the maps created in Tiled, and used in G2DP, require three layers. That is a requirement. One layer named “PLATFORMS”, one layer named “FOREGROUND”, and one layer named, you guessed it, “BACKGROUND”.

You do not necessarily have to put any tiles in the foreground or the background. The map renderer just looks for it, and I think it’s a good property for a two-dimensional platform map to have. Like a bald guy with “hair colour” on his drivers license.

The “background” of the Tiled map relates to just the individual tiles that the hero does not come in contact with. Therefore, “backdrop” refers to the screen’s background. I’m not trying to step on any toes, but that seems less confusing for me.

Today started out with the intention of coding a backdrop layer manager, but the plan quickly diverted to fixing the hero’s “wiggle walk”. What is a wiggle walk, I hear you ask? Ever see a kid playing with paper cut-outs glued to a popsicle stick? That’s what I’m calling a wiggle walk. I’m foregoing any player walking animations for a (more charming?) rotation of the hero’s image. I can’t make it work in print, so you’ll have to see for yourself soon enough.

And in case I piqued any interest about the “backdrop layer manager”, it’s just a system of rendering layers of images in such a way that an illusion of depth is added to the background. It simulates the same sensation as when you are driving down a country road and, off in the distance, you see a barn slowly travel across your field of view. But along the side of the road, fence posts zoom by at the speed of the car.

There was a nice article and demonstration in Flash that I found a while back. I can’t find it, though.

I’ll leave you with a nice screenshot of what is the beginning of the backdrop layer manager.

Earlier this week, I ran into a problem with the hero getting stuck between tiles. Now, he didn’t fall between them, he just simply stopped moving as if he were colliding with a wall. This was no good, as he was simply walking along a flat surface. This may be a small limitation of the Phys2d engine, but I am certainly not complaining. The solution was actually pretty simple.

Rather than create n number of bodies for n number of tiles, I scan the world and create one long, stretched body for the entire span of adjacent platform tiles. This does not cut down the number of bodies to the bare minimum, as I have a feeling I may be able to subtract the platform tiles from a much larger body, and then invert the values when the scan is done. Still, counting the number of bodies above, the static bodies, the ones that never move, I see 18. That’s certainly a lot fewer than even the number of tiles used in only the first 5 lines of the map.

Now the hero has flat surfaces to walk on and the number of bodies to keep in memory have been reduced.

Source code snippet/solution found here on the Slick forums.