George's XNA Programming

According to the XNA team at Microsoft, we will see an update of XNA Game Studio Express somewhere in April of this year. Looks like the members of the XNA team have seriously taken into consideration the feedback coming from XNA Game Studio Express users. I assume that there are quite many improvements. From the most important improvements (at least from my perspective), I would mention the following:

1. Full support for Windows Vista. (Cool, I can now upgrade to Vista as I was reluctant to do so because of XNA Game Studio Express).

2. Bitmap font support (at the moment, as you might be aware XNA does not support bitmap fonts, so we have to resort to our own implementation or third party solutions like Nuclex fonts).

3. Math API improvements. No specifics on what is improved but...

4. BasicEffect will support per-pixel lighting, which is fantastic.

5. Support for volume textures (Texture3D).

6. Ability to read Vertex and Index buffers from Model types.

7. Sharing games with other developers will be extremely easy. It will be possible to package games in a single file (which can be downloaded or sent via e-mail).

Well, this list is not complete. You may wish to check out the post at the XNA Team Blog for a more detailed list, though I believe even that list does not fully describe all the updates that we will see shortly.

Here comes an updated version of XNASlots.

As you can see from the screen-shot, the game now displays stake, winning and balance information.

It is now possible to specify stake and selected lines and when the slot is spun, correct amount is deducted from the user balance.

You can hit 1, 3, 5, 7, 9 keys on the keyboard to select lines and the Spacebar is used to increase bet.

Maximum bet is $10. This is defined in a new constant named MAX_STAKE.

I use Nuclex fonts to display texts in the game. You can find more information about Nuclex fonts in one of my previous posts.

There are a couple of cosmetic changes to the code. For example, the keyboard input is moved to a new method UpdateInput.

We now deduct user balance after each spin and the Spin method has been amended to reflect this as well.

SelectLines and IncreaseStake are two new functions. As you may guess from the names, the former method select lines and the later increases user stake.

The Draw method has been updated to draw texts on the screen.

The LoadGraphicsContent has been changed to load a font.

The background image has been changed as well. I decided to put the stake, winning, balance panel on the main background.

In the next part, we will add the winning table and more cool stuff.

Download the Source Code

Download Compiled Version

While looking at my blog's statistics, I noticed that I get many visitors searching for slot game implemented in XNA. I decided to dedicate a number of posts to building a simple slot game in Microsoft XNA. I will start from a very simple demo game and ultimately grow the project to a full-featured slot game.

We will be developing a multi-line video slots game. More specifically, our slot game will have 5 columns and 3 visible lines as shown on the game screen-shot.

In this type of slots, there are 9 playing lines and a user can choose which lines he/she wants to play.

The heart of the game is a class, which I have named Reel. This class is in charge of rendering and animating the slot symbols on the screen.

In the image on the left, you can see the texture that we will be using for our slot game. The actual texture is a 800 x 1920 pixel image, which contains 12 rows and 5 columns. Each column corresponds to a single reel and each row corresponds to a stop or position (i.e. the symbol) on the reel. The texture width and height are multiples of 4 and thus we can use the XNA compression to reduce the file size of the texture. The nice looking symbols are taken from Microsoft's Office Clips Online web site.

Our reel will be using a virtual stop table. I will be describing the virtual table in an upcoming part but for now let's concentrate on the visual side of the game.

Each symbol corresponds to a stop on the reel. Let's agree that we call Stop 1 such a position of the reel when the lowest symbol on a column is located at the bottom line.

For example, if we take the first column, its Stop 1 corresponds to a position where the bottom 3 symbols (pineapple, coconut, berry) are visible on the screen. Stop 2 is when watermelon, pineapple and coconut are visible and so on. Thus, Stop 12 will be when the coconut, berry and cherry are visible on the screen. Please look at the illustration below to make sure that you have a correct understanding. 

You can download the source code and play with it. I have also put a compiled version for you to test. Run the application and hit the S key on the keyboard to spin.

Our Reel class is extremely flexible. If you wanted to make a single line slots game, all you had to do is to change the REEL_LINES constant value from 3 to 1.

In the next part we will add some labels on the screen so that we display different information (lines selected, balance, winnings) to the user.

Download the Source Code

Download Compiled Version

Collision detection is probably one of the trickiest things in game development. A major problem associated with collision detection is that as the number of objects increases for which you need to check whether they collide or not, performance of the game drops. With a couple of sprites you may not even notice any performance issues, but when the number of sprites becomes relatively high (a machine gun is a good example) performance may seriously suffer. Things get worse when you need to detect collision between animated sprites.

The aim of this post is to give you a number of links where you can find how other folks implement collision detection. A general approach is a two-stage process. The first stage is to check for potential collisions using a bounding box. If the first stage reveals a potential collision, the next stage is to perform a pixel level collision detection.

Gary Kacmarcik has collision detection implemented in his XNAExtras. A good feature of Gary's method is that you can set if you need a pixel level detection or if the bounding box detection is enough. You can read more at http://blogs.msdn.com/garykac/archive/2006/09/24/769335.aspx.

Another destination that I can recommend is an article by Michael Morton, which can be found here: http://www.ziggyware.com/readarticle.php?article_id=48. I would also recommend reading another, more advanced article by Michael, where he expands his method to rotated sprites. It can be found here: http://www.ziggyware.com/readarticle.php?article_id=52

Chris Taylor's article is also very good and provides enough theory in a short but easy to understand manner: http://dotnetjunkies.com/WebLog/chris.taylor/archive/2006/09/30/148798.aspx.

Many industries (and I would dare to say, the whole history) develop in cycles. Game development is no exception. In the beginning (for some people this may be DOS era, for some even earlier, mainframe era) games were extremely simple and boring and were developed by individual programmers. Then games became more interesting with nicer animation and effect but still game development was more of a hobby. Gradually (and this has not happened overnight) game development became teamwork and ultimately the craft of companies which over time turned into large corporations.

Looking realistically, today it is (nearly) impossible for an individual to develop a successful commercial game. Yes true, you may come up with an excellent game concept but turning that into an actual game is virtually impossible. Even for small teams it is extremely difficult next to impossible to compete with large game development houses.

With the introduction of XNA, Microsoft is making an attempt to give individuals (but more realistically to small teams of 3-5 people) a chance to create games that may become commercially successful. This hypothesis is further strengthened by the fact that a game developed with XNA runs both on PC and on XBOX (and maybe on Linux in a near future).

But we should not forget that actual game development is just a starting point. Once a game is developed it needs marketing and distribution. This is especially true for games targeted to XBOX.

Anyhow, only time can show if time has comes for small teams and individuals to enter the commercial gaming market. Personally, I believe that a new strategic window is opening in the game development and this industry will see considerable change within 5 years from now.