Thursday, April 19, 2012

Porting Deadly Dodge Ball

I have been slowly moving away from Flash towards HTML 5 for a while with 12 Months of Doomsday most likely being my last Flash project. It is certainly possible that Flash CS6 will somehow convince me to keep developing for Flash, but Adobe has pissed me off quite a bit the last few months so CS6 would have to have extremely impressive features (or a really cheap upgrade from CS5.5) in order to keep me as a customer. For this reason I decided to port my Friday the 13th project from Flash to HTML 5. If porting from Flash to HTML 5 wasn't enough, I thought it would also be a good opportunity to play around with EaselJS, which is a Flash-like animation library for JavaScript.

The reason I thought about using a third-party (open source) library instead of cleaning up and building on top of my own is simply due to the fact that going forward I am going to have less time to spend on my site as I am going to be focused on developing some mobile games. By using a third-party library, I don't have to worry about the low level graphics code and can focus my limited time creating games. There are a lot of choices available, but I decided to go with EaselJS because it is similar to Flash and is being used by a couple of other projects so it has some chance to stay around.

EaselJS is not vector based, but instead relies on image strips. Flash has a feature that lets you export an animation as a series of image files so I used this feature to create the fireball. This left me with a large number of files that had to be combined into an image strip. Sure, it is possible to load the images by hand into a paint program and assemble the image strip but there must be a tool that does this. A quick search for such a tool lead me to Texture Packer. While this is a paid tool, it does have a free version that simply restricts you to the more essential features. This provides enough capability to create image strips for games. As I happen to write a development blog, the author of the tool was kind enough to give me a key for the full version. With that disclaimer out of the way, I do suggest that if you need to take a number of individual frames of animation and turn them into an image strip that you take a look at this tool.

With the movie clip converted into an image strip it was fairly easy to move the code over to JavaScript.  The big difference was that the stage does not automatically update itself but requires you call an update function. This is not that huge of a deal as there is a built-in timer class that lets you call a tick function which can be used to call the stage update function. Of course, you also have to remember to change getTimer() into Ticker.getTime() and a few other minor differences, but overall the library feels enough like Flash that it was not too difficult to transition to. It is certainly a library that I will be playing around with in the future.

For those of you interested in either of these tools, EaselJS is located at and Texture Packer is located at

Friday, April 6, 2012

Easter Egg Hunt

I am a bit late writing this this week. I normally post my site and this blog on thursday evening as that way I can keep my friday's free. This week I ended up going out on thursday. Last week on Blazing Games, I posted the open source version of my Easter Egg Hunt game where you navigate a 3D maze in order to find a dozen easter eggs. The eggs are randomly generated. The 3D maze was generated using a very old technique known as the painter's algorithm. I was thinking that none of the techniques used in the game are overly noteworthy then I realized that a lot of the techniques in the game, while not useful when you have OpenGL (including ES and WebGL) to work with, may still be relevant if you were limited to a 2D drawing system like the HTML 5 Canvas. HTML 5 developers, at least the ones that are targeting Internet Explorer, may need to  fall back on these old techniques. This is due to MS deciding not to support WebGL.

The egg is simply a palette swapping varient. There are 12 patterns for the eggs, but the two colours that are used to draw the pattern are randomly selected. This is a really old technique that you will see in older video games where the same monster sprite is used repeatedly but given different colours so the same artwork can be used for a large number of monsters. This would be a little tricky to do with the HTML 5 canvas as I don't recall a way of changing an image's palette. I would have to look into this, but if you can't change the palette, you can use the image data to manipulate individual pixels.

The 3D maze uses a technique known as the painters algorithm. Essentially you treat the 3D maze as a series of blocks. You draw the furthest away blocks first, then the nearer blocks, and so on until you are painting the close blocks. The downside to this is you are potentially overdrawing many times. The nice thing about this technique is it is very easy to implement and the results can look very good. Of course, you aren't going to get 360 degrees of smooth scrolling movement, but it is something that can be done on any browser that supports the canvas.

It would be nice if there was a hardware accelerated 3D standard that would work on all browsers, but even if that does happen, it won't be for years. Perhaps for next Easter, I will port the game to HTML 5, though I am hoping I come up with a far better idea for an Easter game before then.