Building a pseudo-3d game using SilverTile

27. juli 2010

I needed a break from my Zelda remake and decided to try something completely different. Being a fan of the Dungeon Master and Eye of the Beholder games I decided to build a 3d-engine for that kind of game.

 

A scene from Dungeon Master - tasty monsters!

The principle is simple - you only allow the player to turn 90 degrees and the entire world is built up of square blocks. When the player moves he always moves one square at a time. This means that we don't need 3d models of everything, 2d sprites are enough. All we need is to draw everything from all four sides and we are done! We get the 3d effect by drawing the objects furthest away before those that are closer.

Creating the effect in SilverTile

Doing this in SilverTile turned out to be quite easy. SilverTile already supports layering of sprites, it supports sprites of any size at any location and it supports transparent pixels. The major job was to decide where to place each sprite. We have three images for walls on each z-level supported by the game - front facing, left and right.

 

Wall tiles: Left, front facing, right

The screenshot below shows a screenshot from the game engine. The wall on the left is made up by three images stiched together, the floor and roof are static pictures.

A screenshot from the game engine running in Silverlight

The figure below shows and overhead view of the rendered scene. The red squares are walls and the green are floor.

The wall layout rendered in the screen shot

I have built a prototype game that runs in both Silverlight and on Windows Phone 7. The game lets you explare a randomly generated maze and is controlled by using the arrow keys on Silverlight and touch gestures on WP7.

The game runs on Windows Phone 7 as well as on Silverlight

You can try the Silverlight verison here. Contact me if you are interested in the source code. The game uses an unreleased version of Silvertile and the source code is quite messy (a real prototype!), so I won't post it here. :-)

 

Update (27. september 2010):

I decided to use my code and build a simple dungeon exploration game and submit it to the Norwegian Windows Phone 7 developer contest. I got a designer buddy (@hiemil) to make a pretty user interface, and I borrowed Ralf Hinrichsens custom DMJava graphics to draw the dungeon and the monsters. The end result was a much prettier game than what you can see on the screens here. Watch a short gameplay video here:

 

 

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New version of the sample application is ready.

8. april 2010

Edit:

I found a few nasty bugs in this version, so I uploaded a new one. This version also has even more monsters to hunt, so have fun!

 

Try it here!

The game is only available in Silverlight 4 at the moment.

 

New monsters!

Any comments?

Bugs?

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SilverTile needs your help!

9. mars 2010

A few days ago I discovered a very interesting project. Ryan Corradini has a project named Canvassa that is a HTML5/Canvas based Zelda clone. He does more or less the same thing I do with SilverTile but his approach is quite different. His blog is quite interesting and especially the posts about reverse engineering the game map based on a huge picture was very interesting.

Canvassa

 

Inspired by Ryans posts I wrote a simple C# program that would parse the entire map for The Legend of Zelda (I found the map here) and spit out tile images and Xaml code that SilverTile could utilize. (More on this in a later post - it was quite fun actually!)

The entire game world - click the image for the full 4096 pixel wide version

 

With this in place I think SilverTile is ready to be tested by a broader audience than me and a couple of friends. So that is where you dear reader come in.

I need you to test out two versions of SilverTile, one running under Silverlight 4 beta and one running under Silverlight 3. If you only have Silverlight 3 installed then just run that one. :-) What I am after is feedback on wheter I need to optimize the game engine or not. In its current state the engine is full of naive implementations that could probably be easily optimized, but I don't want to spend unnecessary time on it. I am also interested in getting feedback on the game engine itself. Does it work? Is it playable? What should I change?

Monsters! This is what awaits you if you move left from the start area

 

Once the game is running you can control your character using the arrow keys. Move to the open edges on the screen to visit other areas of the game world. If you move to the left you will face hordes of enemies and if you move up you will face a few enemies. All other areas are empty, and you cannot fight the monsters at the moment. If you die just reload the page to start again.

What I want you to do is the following:

  • First move around the screen and see if you can control the player sprite properly.
  • Then move up to the next area and see if the monsters run around more or less randomly. If you run into a monster your life (the hearts) should decrease.
  • Then move back down and to the left. Here you will meet a huge number of monsters. Watch the monster counter and let me know how many monsters there are when the game starts to feel sluggish. Aslo watch the frame rate counter in the bottom of your browser window. It should be around 38-40. How long can you survive before the monsters eat you?
  • Finally explore the map a little and see how this works. Does the game engine crash or behave strangely?

 

When you are done testing I want you to leave a comment to let me know what kind of computer you are running and what your results were. I am particularily interested in hearing how many monsters the game engine could handle and if you experience anything strange. Which operating system and browser you are using is also interesting.

Click here for the Silverlight 4 version and here for the Silerlight 3 version.

Thanks in advance for helping!

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SilverTile: Working on the game

22. februar 2010

It's time for another project update.

I just uploaded a new version of the SilverTile sample application. The new version has four areas that you can move between freely and lots of monsters you can hunt. The monsters have different AI, the blue ones will try to hunt you while the red ones will move randomly.

Lots of dangerous monsters!

Since my last update I have added some features to the game engine:

  • A simple keyboard input handler
  • Improved area transitions
  • Improved collision detection
  • Layering of sprites (z-index)
  • Improvements to the monster spawning process

All the changes I have done are based on the needs of my sample game. A more structured keyboard input was needed as the complexity of the game grew.

Area transitions needed to be directional so that you can transition into a tile with an area transition back without being stuck in an endless loop.

I found some bugs in the collision detection algorithm that I fixed (Yay for TDD!), but my implementation is really naive. I would be grateful if anyone could help with a better algorithm. :-)

Layering of sprites was something I really wanted the engine to have, but I didn't need it until I was to render the players sword. The sword is drawn underneath the player sprite when the attack animation starts, and I needed to make sure the sword wasn't draw on top of the player.

The monster spawning process was modified so that monsters can be spawned immediately when a level is loaded. The classic The Legend of Zelda spawns enemies this way, so I need to support it.

All game levels were drawn using the editor application I wrote. The application is really simple, but it allows me to draw the game levels and export them as Xaml easily, so I am happy with it.

Whats next

With a more complete game engine I think it is time to build a better user interface for the game. I have added hit points to the player, but I need to display them as hearts as in the classic Zelda.

I also need to build more game levels and start adding items to the game. Monsters should drop coins that you can use to buy stuff.

And then I need to add text rendering and an intro screen and a game over screen!

... So there is still lots of work to do.

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SilverTile: Another progress report

17. desember 2009

It's time I posted another progress report.

Since my last progress report I have implemented most of the features from my feature list. I'm not entirely happy about the Xaml support for level design, and I am still missing the support for per-pixel collision detection, but the game engine works well enough that I have implemented a VERY simple game using it. 

The game, available here, lets you control your character on a field throwing swords at some monsters. You get points for how many monsters you kill and if you are touched by a monster you die. 

Hunting monsters

Hunting monsters

As simple as it is the game demonstrates the features needed for a proper game:

  • We have collision detection - both between moving sprites (character, monster, sword) and between sprites and background (you cannot walk across mountains). 
  • We have animation support and an animated sprite can have many animations that we can choose.
  • The game area and all game assets are defined in Xaml. 
  • Graphics are reused between sprites. This means that two identical monsters share the same bitmaps in memory.

The engine is still missing some features. The most obvious one is the pixel perfect collision detection. This is a simple feature to add, but I fear that it will be a real performance killer so I postpone it until I really need it. Apart from that I feel that the framework surrounding game setup needs some work.

The current implementation lets you define one or many GameAreaGrid objects. The GameAreaGrid lets you place one rectangular sprite in each cell. You then tell the Viewport to load the grid and it will be setup as the background area of your game. To change maps you tell the viewport to load another GameAreaGrid object.

While this works well enough I would like it to be even simpler to use.

The idea is to add support for area transitions to cells in the GameAreaGrid so that when the player enters one of these we automatically loads the new grid and places the player at the new location. This should allow us to setup an entire game world using only Xaml. I'm not entirely sure what would be the best way to define an area transition but I think it would be nice to add an AreaTransitions collection property to the GameAreaGrid where each object in the collection described a transition that would be performed when the player enters a given cell. A transition would be from a cell (grid row and column) to a new cell in another GameAreaGrid. The reference to the GameAreaGrid would be a regular object reference that could be modeled as a binding to a StaticResource in Xaml. This still gives us the option of designing the GameAreaGrid in Xaml or in code if we prefer. 

I would also like to allow random placement of enemies in a GameAreaGrid. Either completely random or by identifying cells where mosnters can spawn. The types of monsters, the number of monsters and how often they spawn would also have to be specified.

So that will be my plan for the week until christmas. Implementing more support for game mechanics, paving the way for a complete game engine :-)

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SilverTile: Old-school gaming on a modern platform - progress report

8. desember 2009

It's time for a progress report.

The last week I have been adding basic features to SilverTile. The first feature was to add basic rendering support. My first attempt used Array-copy functions to copy pixel data from the sprite to the viewport. This worked well, but it did not support alpha blending (transparency) of pixel data. To improve this I added some code from the Silverlight Games 101 blog that allowed rendering of bitmap data from one WriteableBitmap to another. I modified the code somewhat to support rendering of data from any IRenderable and then I had the rendering support I needed.

The intial architecture of SilverTile defined each sprite object as having its own pixel data. This is fine as long as you have only a few sprites or if each sprite have an unique appearance, but in most cases you will have many sprites using the same image. One example is the walls of a game area. I model each wall segment as an unique sprite, but each is built up of the same image. So instead of having each sprite have its own pixel data I refactored out the pixel data into a Frame object that could be reused between sprites. This also lay the ground for animation support later.

Zelda walking

Link walking!

To set up a game area I want to support two modes. One mode should be building game areas in code by using the AddBackgroundSprite() method of the Viewport class. This lets you add one sprite at a time at the desired location. While building the game area in code works well, I wanted to support using Xaml to describe the game area and the graphical resources used by a game. Since Silverlight only allows classes that inherit from UIElement to be named (given the x:Name and x:key attributes) in Xaml I had a choice of either letting the Sprite classes derive from UIElement or using a separate set of classes to describe the game area. I cholse the latter option and built a set of classes that can be instansiated in Xaml and that describes a game area, a game tile and a frame. I then added a SetGameArea helper method to the viewport that reads the GameArea data and performs the setup.

Finally I added support for animated sprites. An animation is a list of IFrame objects in combination with a frame rate. Each time the Update method of the animated sprite is called, we check if the elapsed time is greater than the time a frame should last and if it is we switch frames to the next frame. When we reach the last frame in the animation we go back to the first frame again. Although I will need for sprites to support multiple animations (like walk left and walk right), this is a good starting point.

On top of all this I have written tests for everything. This really helped me when refactoring the code to use IFrame and the bitmap blitting.

If you have the Silverlight 4 beta installed you can watch a live demo here: http://rag.no/st/silvertile.html. (Try clicking on the game area!) Or you can download the source code here: http://silvertile.codeplex.com/

 

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SilverTile: Old-school gaming on a modern platform (part 2)

3. desember 2009

I will try to keep SilverTile simple with just the features needed to get my game running.

At the very least SilverTile will support the following:

  • Rendering to a surface (WriteableBitmap)
    • I think this is the fastest way to render pixel graphics in Silverlight (done)
  • Support both tiles for background / terrain, and moveable sprites
    • Sprites should support animation (done)
    • Sprites should support transparent pixels (done)
  • XAML for game level setup
    • Support using XAML to setup the game levels/maps (done)
    • SUpport using XAML to define sprites and animated sprites (done)
  • Collision detection
    • Tiles should support bounding-box collision detection (done)
    • Sprites should support bounding-box collision detection (done) and possibly per-pixel collision detection (not yet)
  • Input control
    • Keyboard input should be handled in a structured way
  • Game infrastructure support
    • Support for transitions between levels/maps defined in XAML (done)

In addition I think SilverTile needs a way to handle the game and a game session as an entity, but that can wait until later. This is implemented in the SilverTileGameWorld class.

Any comments? Did I forget anything essential? I will update this page with any new features and with some progress information as soon as I have anything to report.

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SilverTile: Old-school gaming on a modern platform (part 1 of many)

30. november 2009

This is the start of my developer diary for SilverTile. The diary is mainly for my own use both as a reference and as a way to document my progress. Hopefully I will end up with a useable solution one day.

Silvertile? What is it?

The last few months I've been experimenting with Silverlight programming. I've written all kinds of database-driven applications and have experimented with various different programming models. While this has been rewarding and I've learned much, it hasn't excactly been coding for fun.

For a while I participated in the development of Smeedee, a project monitor for agile projects, and that was fun - but lately I've been playing with my own project again. As all good nerds know, writing a game is the most entertaining way you can learn a new programming language or platform. So that is what I've been doing. Being a fan of old-school games I decided to write a remake of a real classic – the original Zelda for the NES-platform. The game itself is simple, but it is fun to play and writing a remake should be a fun challenge.

Zelda

Good old Zelda - coming to Silverlight?


Writing games is a fun excercise itself, but it gets even more fun if you end up with something that can be reused later. That is the reason I am writing about SilverTile and not SilverlightZelda - I am writing a reuseable library for old-school games. :-) The library itself will be quite simple, but I plan to include XAML support for graphics and level design.

Can I use it? Does it work?

I have created a project for SilverTile on Codeplex, but the source code there is more or less unusable. I have been using it as a test bench for the architecture and design of the library and I don't think anyone will be able to use it. As soon as I have some usable code I will upload it to the project.

So then. I'll get back to the coding. Hopefully I will have more to show soon. :-)

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