Even when I did not post much last week I was very busy converting all the old XNA 1.0 games to XNA 2.0. I did not only convert all projects (8 games in total, see below), but I also tested them extensively on Windows XP, Vista (32 and 64 bit) and the Xbox 360. Additionally a lot of usability improvements have been implemented in the games, for example the XNA Shooter is now much easier (was almost impossible to even reach 50% of the level) and a lot more fun due better balancing. The XNA Racing Game has now a better physic engine and will not longer let the car fly out of the track or leave ground in loopings. Due the better input control and fixed physics the cars drive now much faster and it is more challenging to complete the tracks in shorter time frames.

Games in this article:

• Chapter1Game
• Xna Pong
• Xna Breakout
• Xna Tetris
• Rocket Commander Xna
• Xna Shooter
• Xna Racing Game
• Dungeon Quest GDC

Please read my previous post about Converting XNA 1.0 games to XNA 2.0 for all technical tips. All the games can also be found on http://XnaProjects.net, but I will also make them easier accessible on this blog soon, which has an update overdue (need to clean up the left and right sides) ^^

Thanks to the great VS2005 support of XNA 2.0 all games have now just one single solution file, which works on Windows and the Xbox 360. The projects can be opened in XNA Game Studio 2.0 and Visual Studio 2005 without having to convert the files over and over again like in the past. The Icons for all games were also improved. Lets take a look at the Icons (.ico files) on Windows:


For the Xbox 360 game icons the .png files (usually named GameThumbnail.png) are used:


Ok, let's take a look at the games and what has changed for them. Most games are pretty much the same as for XNA 1.0, but a lot of smaller bugs were fixed and they have been tested more.

• Chapter1Game: This application is not really a game, but a test project to check out if XNA 2.0 is properly working on both Windows and the Xbox 360. It is from the first chapter of my book "Professional XNA Game Programming". BTW: The second edition of the book is coming out soon, there are 3 more chapters about Multiplayer game programming and a cool new role playing game.
  
  
  • Game Installer: Chapter1GameSetup.exe (210 KB)
  • Source Code and Game Content: Chapter1GameSourceCode.zip (57 KB)
  • Screenshot:
    
    
    
• Xna Pong: Xna Pong is a simple clone of the favorite pong game from 1978. It is just a few hunderd lines of code and should be very easy to understand.
  
  This game is from the book "Professional XNA Game Programming" by Benjamin Nitschke. For more information read chapter 2. (2008-02-10: Now updated to XNA 2.0)
  
  
  • Game Installer: XnaPongSetup.exe (309 KB)
  • Source Code and Game Content: XnaPongSourceCode.zip (258 KB)
  • Screenshot:
    
    
    
• Xna Breakout: XNA Breakout is a simple Breakout/Arcanoid game based on the XNA Pong game from the previous chapter.
  
  It is fully described and covered in Chapter 3 of my book "Professional XNA Game Programming". The code is quite short and should be easy to understand. (2008-02-10: Now updated to XNA 2.0)
  
  
  • Game Installer: XnaBreakoutSetup.exe (383 KB)
  • Source Code and Game Content: XnaBreakoutSourceCode.zip (316 KB)
  • Screenshot:
    
    
    
• Xna Tetris: This is a simple, but highly addictive Tetris game. You can control the blocks with your cursor keys, aswd or a game pad and the game works both on Windows and the Xbox 360. Reaching levels above 5 is really hard. My highest level was 9, try to reach more :) (2008-02-10: Now updated to XNA 2.0)
  
  This game introduces the helper classes (chapter 4 of my book) and makes more use of unit testing and game components in XNA.
  
  
  • Game Installer: XnaTetrisSetup.exe (310 KB)
  • Source Code and Game Content: XnaTetrisSourceCode.zip (277 KB)
  • Screenshot:
    
    
    
• Rocket Commander Xna: XNA port of the famous Rocket Commander game. The game principle stayed the same, but the controls were a little bit simplified to make it more fun on the Xbox 360.
  
  If you want to learn more about the Rocket Commander game, check out its official website www.RocketCommander.com and check out the Video Tutorials on Coding4Fun by MSDN. (2008-02-10: Now updated to XNA 2.0, also supports very big resolutions now and runs faster on the Xbox 360)
  
  
  • Game Installer: RocketCommanderXnaSetup.exe (16.5 MB)
  • Source Code and Game Content: RocketCommanderXnaSourceCode.zip (52.8 MB)
  • Screenshot:
    
    
    
• Xna Shooter: Shoot'n'up game specifically created for my book "Professional XNA Game Programming". It features full HDTV support, runs on Windows and the Xbox 360, 5 weapon types, 5 enemy types, a powerful ship and some power ups. It is quite fun to play and it gets harder and harder the longer you play. Based partly on the Rocket Commander XNA engine, but also features lots of new effects and shaders. (2008-02-10: Now updated to XNA 2.0, also much easier and balanced)
  
  This game and the racing game are the most improved. The game works now much better in high resolutions and on the Xbox 360. But most importantly the game is now much easier, balanced and more fun. Additionally a level percentage is now visible on the bottom and more EMP bombs can be picked up to make it easier at the end of the level.
  
  • Game Installer: XnaShooterSetup.exe (14.9 MB)
  • Source Code and Game Content: XnaShooterSourceCode.zip (32.2 MB)
  • Screenshot:
    
    
    
• Xna Racing Game: XNA Racing Game Starter Kit I wrote for http://creators.xna.com. More information and more downloads can be found on http://XnaRacingGame.com. It runs best on the Xbox 360 in HDTV (1920x1200), but it also runs fine on the PC. (2008-02-10: Now updated to XNA 2.0, driving also improved a lot, better tested on Xbox 360 and fixed some issues).
  
  Following things were improved: Shadow mapping on very big resolutions works now (crashed before), more options for lower quality settings, fixed physics, car now always stays on the road, fixed loopings, cars are much faster now, winning conditions work better now, and fixed several other bugs.
  
  • Game Installer: XnaRacingGameSetup.exe (40.2 MB)
  • Source Code and Game Content: XnaRacingGameSourceCode.zip (95.4 MB)
  • Screenshot:
    
    
    
• Dungeon Quest GDC: And finally the Dungeon Quest XNA Game, which was developed in just 4 days on the GDC 2007 at the XNA Contest. Dungeon Quest GDC is a relatively complex 3D role playing game (at least for just 4 days of work). An early version even supported coop multiplayer on the Xbox 360 via splitscreen. The game was developed by Benjamin Nitschke (abi.exDream.com) and Christoph Rienaecker (WAII). (2008-02-10: Now updated to XNA 2.0). This is NOT the full Dungeon Quest game (see www.DungeonQuestGame.com for that), this is just the GDC version.
  
  Please note that the level was reduced to allow loading on the Xbox 360 (which otherwise crashes with an OutOfMemoryException), the game is not fully playable, only the first part is implemented. You can also press F2 to toggle the Options menu and some minor bugs were fixed. But this game is no longer supported, I will not improve it anymore! Please check out the new Dungeon Quest game from www.DungeonQuestGame.com, which is coming in a month or so.
  
  • Game Installer: DungeonQuestGDCSetup.exe (25.6 MB)
  • Source Code and Game Content: DungeonQuestGDCSourceCode.zip (67.2 MB)
  • Screenshot:
    
    
    

Have fun with all the games :)

When I wrote this (a little bit each day while working on converting the old XNA projects) I was very aware about the disappointment of my blog readers about the fact that I did not blog much in the last couple of months, especially on XNA. I not only got a lot of emails about that, but also quite a lot of questions, especially since XNA 2.0 was released. I made yet another promise to myself to change that and finally blog more, maybe not only when something very interesting pops up, but instead about the everyday issues I run into.

Some Notes about XNA 2.0: More solid, lots of little new features, networking, while it may not be a very complete solution, at least it is now possible on the Xbox 360 and overall I have the feeling even more people are interested in XNA than a year ago. Plus the guys at the XNA Team doing a great job and are constantly improving the XNA Creators Club website for us game programmers and artists :)


Several people had problems using the old XNA 1.0 code of my games and make them work with XNA 2.0, so here is a little help in case you want to convert XNA 1.0 projects to XNA 2.0. You will also notice this if you go to any XNA community site as most samples will still be in XNA 1.0 and not work out of the box in XNA 2.0, and many of those will probably never be changed since they are not longer actively being developed.

For most games almost all of the code can stay unchanged, you just have to poke at a few things that have changed in the framework or were improved. More information about converting projects can be found here (read this first, this article is based on the stuff there). You can also use the Cross-Platform Game Project Converter from XNA 2.0 to add a Xbox 360 project to your existing Windows XNA project without having to create a separate project (it is helpful, but I used pretty much the same trick for all of my XNA 1.0 games anyway).

Let's go through the steps:

1. Either use the XNA project conversion utility (can be found on the XNA Creators Club website) or just create a new XNA 2.0 project in VS 2005.
   
   
2. If you created a new project, drag all source code files into the project and seperate the content files out and put them all in the existing Content directory (only there the content pipeline is activated). If you just converted a project and the content files did not move, move them yourself to the content directory. Gladly all my projects with more than 5 content files had a special content directory anyway, so no need to change anything content-wise for them. If you don't want some of the files to be compiled to .xnb files, you have to change the build action from "compile" to "content" (and then use the "copy to output directory" switch) or to "none" if you want them to be ignored like for .wav files, which are automatically processed by the .xct (XACT) file for you.
   
   
3. Find the line content = new ContentManager(Services); and replace it with Content.RootDirectory = "Content";. If you do that, get rid of the content manager in your game class since you can now use the build-in Content property to access the underlying Game content manager. In case you don't want to do that or if you need an extra variable, replace the above line with content = new ContentManager(Services, "Content");. Both ways will make sure all the content is now loaded from the content directory instead from the main directory of the application. In more complex XNA games you can also change the BaseGameDirectory to the content directory, but then you would also have to move all other resource files to this directory (config files, save games, levels, etc.). It is usually a good idea to separate the compiled (.xnb) content from the content the user can change (config, levels, etc.), so I suggest just redirecting the content directory of the content manager.
   
   
4. Replace the LoadGraphicsContent(bool) method with LoadContent, remove all the if (loadAllContent) commands (was never false anyway, just let the content of the if loop stay) and also remove the call to base.LoadGraphicsContent(bool) (does not do anything like all the Load or Unload methods in the XNA Game class, they are just empty virtual methods). You can also ignore this and the next step since it will only generate depreciated warnings, but I suggest cleaning up your source code whenever an opportunity like this presents itself. I also added some missing region blocks to the code and some comments here and there were they were missing.
   
   
5. Finally delete the UnloadGraphicsContent method unless it did anything beside base.Unload and base.UnloadGraphicsContent. In my XNA games the UnloadGraphicsContent usually looked like this and can be safely removed now (at least if nothing else is in there):

/// <summary>
/// Unload graphic content if the device gets lost.
/// </summary>
/// <param name="unloadAllContent">Unload everything?</param>
protected override void UnloadGraphicsContent(bool unloadAllContent)
{
  if (unloadAllContent == true)
    content.Unload();

  base.UnloadGraphicsContent(unloadAllContent);
} // UnloadGraphicsContent(loadAllContent)



6. In case you load sound and music via the AudioEngine, you have to change the directory to the content directory too, which will not be done automatically for you since you load the .xct file directly in the AudioEngine constructor. Basically just exchange the following code:
   
   

   audioEngine = new AudioEngine("YourSound.xgs");
   waveBank = new WaveBank(audioEngine, "Wave Bank.xwb");
   soundBank = new SoundBank(audioEngine, "Sound Bank.xsb");
   

   with:
   

   audioEngine = new AudioEngine("Content\\YourSound.xgs");
   waveBank = new WaveBank(audioEngine, "Content\\Wave Bank.xwb");
   soundBank = new SoundBank(audioEngine, "Content\\Sound Bank.xsb");

      
   
7. In case you have used the StorageDevice and specifically the ShowStorageDeviceGuide helper method, it is gone now in XNA 2.0. I had it in some helper classes, but never actually used it. In case you want to show a save game dialog (or some network game select dialog for example), please follow the XNA 2.0 help instructions to do this asynchronously now.
   
   
8. In case you use any ResourceUsage enum, replace it with TextureUsage instead or remove it if the issue is not texture related. You can also safely remove any ResourceManagementMode.Automatic parameters, which are not longer supported. Everything is now automatic anyway. Just if you have been using ResourceUsage.RenderTarget you will need to change the Texture2D class to a ResolveTexture2D class in order to archive the same behaviour as before. Some calls to the device (e.g. ResolveBackBuffer) have also changed and require a ResolveTexture2D now. You may also want to check if you have any manual texture management or disposing, which you can remove or simplify.
   
   
9. For simpler games (2D) games you should be done now. More complex games using render targets and other features that have changed in XNA 2.0 will require some more changes, but after you have done them once (or know where to change what) this is also a quick process.

The following only applies to the RocketCommanderXna, XnaShooter and XnaRacingGame engines, but you might find similarities with other XNA games and the converting process:

1. First of all make sure the old XNA 1.1 code gets compileable by going though the changes mentioned above (e.g. replacing ResourceUsage with TextureUsage or BufferUsage) and removing everything that does not exist anymore (like ResourceManagementMode.Automatic). If a method is non-existent in XNA 2.0 like ResolveRenderTarget, comment it out and remember where it happened.
   
   
2. You might go through other issues, but you have to come back to the RenderTarget issue. This took the most time in the converting process for me (probably half of all my issues come by something related to changes with RenderTargets in XNA 2.0). For that reason always make sure that rendering to textures still works while you make changing. I always used the TestCreateRenderToTexture unit test inside the RenderToTexture class to figure things out.
   
   
3. Additionally to making some changes in the BaseGame class (loading content via LoadContent, using the base.Content instead of creating a new content manager, etc.) I also removed all the RenderTarget helper methods and fields from the BaseGame class (SetRenderTarget, ResetRenderTarget, etc.) and moved them into the RenderToTexture class. While this makes the code more clean and restructured by making a few more fields private, if you do not call the new InitializeDepthBufferFormatAndMultisampling of the RenderToTexture class the calls to SetRenderTarget and ResetRenderTarget will not work correctly and will not restore the default depth buffer (which has to be remembered first). If you get the following exception it means the DepthBuffer Device.DepthStencilBuffer was set to null, but is obviously still used. In order to fix that make sure the remDepthBuffer variable is set to a correct value in the InitializeDepthBufferFormatAndMultisampling method!
   


An error has occurred during the Clear operation while trying to clear the depth or stencil buffer, no DepthStencilBuffer surface exists.
System.InvalidOperationException: An error has occurred during the Clear operation while trying to clear the depth or stencil buffer, no DepthStencilBuffer surface exists.
at Microsoft.Xna.Framework.Graphics.GraphicsDevice.Clear(ClearOptions options, Color color, Single depth, Int32 stencil, Rectangle[] regions)
at Microsoft.Xna.Framework.Graphics.GraphicsDevice.Clear(Color color)

   

4. 4. Even if you have now done everything, the app may still crash when you are trying to clear a render target (which usually happens at the start of each pre or post screen shader). The reason for the following error is the multi sampling format, which might be set to the background buffer, but not to the render targets:
   

   
   The active render target and depth stencil surface must have the same pixel size and multisampling type.
   System.InvalidOperationException: The active render target and depth stencil surface must have the same pixel size and multisampling type.
   at Microsoft.Xna.Framework.Graphics.GraphicsDevice.VerifyDepthRenderTargetCompat()
   at Microsoft.Xna.Framework.Graphics.GraphicsDevice.Clear(ClearOptions options, Color color, Single depth, Int32 stencil, Rectangle[] regions)

      
   In order to get rid of this error without changing the RenderToTexture class a lot, you can just comment out the line where multi sampling is activated in BaseGame:
   

   //this.graphics.PreferMultiSampling = true;

There are probably even more things that I forgot while converting the projects (converted 8 games and about 15 projects in total now), but the above list should be helpful. Especially for me because I always forget some of those little things and having this checklist is very helpful.

Tomorrow I will probably test all the XNA 2.0 games on my Xbox 360 and make some final adjustments and then post them all on http://XnaProjects.net (and here).

Yes. My XNA book is finally out and some people even got an early version last week. There is also some discussion going on in the XNA Forums and on the official Wrox forum for the book.

The coolest thing yesterday that my book was on Rank #16 for Computer/Technical books on Amazon.com and on Rank 500 something for all books. Quite impressive if you ask me, hopefully it will continue to stay high and make me filthy rich .. just kidding.

Yesterday I wanted to put all the samples from the book on my blog, but it is already way to overloaded here with screenshots and games, adding another 10 games will not make anything better. Instead I had a crazy idea to create a XNA Community site in one day. It is called XnaProjects.Net. The idea is for everyone to submit their games and links. News are grabbed with Google Blog Search and more features will come in July 2007 when I got more than 5 minutes time in a row.

Anyway, check out this great new website, submit your games and links and check out whats already submitted by me (10 Games so far, yes, thats a lot of XNA games I did in the past few months):

• XNA Pong
• XNA Breakout
• XNA Tetris
• Rocket Commander XNA
• XNA Shooter
• XNA Racing Game
• SimpleRacingGame
• SpeedyRacer
• Dungeon Quest
• Skinning with Collada Models in XNA

You can find source code and game installers for all of these games, including some nice screenshots and a YouTube video for each of them on the XnaProjects.Net website. Check it out:

Sorry for not blogging yesterday. We were working all day on our game here on the GDC 2007 and it was very noisy and distracting here. If you want to watch us work: We are in the Moscone North Lobby and shouldn't be hard to find. Anyway, I will probably just blog at the morning of the next day for each day here.

Our game is called Dungeon Quest and we are absolutely insane because we want to create a Multiplayer Role Playing Game in just 4 days and we haven't even thought of all the distractions here. I will try to give you a screen per day and tell you want we have done so far.

Yesterday we worked purely on the environment, the level and the general game idea and some smaller details. As I said before we started with nothing, I just created a new project and Christoph did just open up 3DS Max and started working, there are no textures or models we have already done. And we both have never worked on a role playing game before.

In the morning we still had a lot of problems getting our computers up and running (3DS Max wasn't starting, I needed lots of plugins and tools, stuff like that). It usually takes a day or more to set up a development machine in our opinion. Probably a week until you got all the important tools installed you forgot in the first day. Anyway, we finally started to build the cave, create new custom collada exporter for that and placed lights. While Christoph was working on the 3D cave I was getting the engine up and running and noticed that there are many things that have to be done:

• Like just rendering some text on the screen,
• Finding a good font for that,
• Creating a bitmap font,
• Also making other UI elements (selected monster, health, level up, etc.)
• Rendering shaders and playing around with point lights
• Working on many other smaller issues like effects, billboards, vertex formats, etc.
• Most unit tests require a good camera and testing the cave level itself was very hard, so I already created the ThridPersonCamera class we going to use for this game.

I started with most classes that are required for that and I also could drop in some Texture/Font code from Rocket Commander XNA, but most of the shader and collada import classes had to be created from scratch. Then we spend all evening and even this morning tweaking the shaders, getting all the lights working, adding fog, figuring out how to do 6 complex light passes in one shader, and so on.

Today we will focus on building the main character, getting some collision detection working and some basic game logic (keys, doors, monster state machines, player behaviour and animations). Hopefully I can provide you with a nicer screenshot tomorrow, just an empty level is pretty boring.

And here are some pictures from yesterday for your enjoyment.

This is the lobby of the Moscone North building at the GDC. The GDC Expo hall is below us and on Monday the Serious Games Summit was here, but we hadn't had any time to even check out who is speaking at the actual GDC. At wednesday I will be at some Collada round table speaking about Collada and issues we had with it so far ^^

There are many art galleries here in San Francisco and the Asian population is also huge. It was not hard to find an Asian Art Gallery.

Here you can see an ad for Microsoft's Vista Operating System directly in front of the big Mac building here (seems a lot of people got one here). There is nothing interesting about a Mac for a game developer IMO.

Alcatraz at day time. I already showed you a picture at night earlier.

A view from my desk at the Hotel over San Francisco. Its still impressive every day you wake up ^^

And some picture of a place I don't know the name of. Usually I would look it up, but I have to go back to work. Cya tomorrow!

Don't ask me how I managed to not post anything this week. My plan was certainly different, but I didn't want to post my problem with this little project too early. To make up with the lack of blog posts this year until now this is going to be a very long and hopefully very useful article

Content

• Video, Screenshot and Downloads
• Introduction and why Collada?
• Class Overview
• Loading collada files
• Problems with the animation data
• Optimizing vertices
• Optimizing the Optimization
• Adjusting the shaders for skinned meshes
• Post screen shaders for the final result
• References and Links

Video, Screenshot and Downloads

First of all, here is a video for the project I'm talking about here:

Screenshot of the same scene (better quality since youtube videos just suck quality wise):

Before you start reading this article I suggest you download the executable and source code first in case you want to try it out directly while reading. The whole project is based on the RocketCommanderXNA engine and just adds the ColladaModel.cs class, which does all the amazing stuff you see in the video The video above shows shadowing from the XNA Shooter engine, which is not yet released and their fore not included in the downloads. The rest of the code is the same, just the shadow map rendering was removed. More details about shadow mapping in XNA can also be found in my book (plug plug plug ^^).

• The source code is about 2.6 MB and contains projects for XNA Game Studio Windows and the Xbox platform, as well as a project for Visual Studio 2005. It was tested on Windows XP and Vista 32 and 64 bit as well as on the Xbox 360.
  SkinningWithColladaModelsInXnaSourceCode.zip (2.6 MB)
• The executable contains the output (32 bit Windows, but runs on 64 bit and Vista too) from the project in case you just want to try it out or do not have XNA Game Studio Express installed yet. You still need the XNA Framework for this program, download it here, if you do not have it installed yet! You also need a Shader Model 2.0 capable graphic card.
  SkinningWithColladaModelsInXnaExecuteable.zip (2.5 MB)
  
  Update 2007-02-26: Fixed time steps, in release mode with more than 200-300 fps the animation was getting too slow. Now works flawless :)
  

Please note that the 3D Goblin Model was created by my friend Christoph Rienaecker (WAII) and if you want to use it, please credit him (see Readme.txt). The source code and collada loading class can be used freely too, but I want some credits too (at least in the source code ^^).

Introduction and why Collada?

OK, let's get started. I talked a lot about the XNA Content Pipeline and its problems on my blog, and in several recent interviews and also in my upcoming XNA book. For projects like Rocket Commander or even the Racing Game it was sometimes a little bit annoying, but I could do everything I needed by loading X files and adding some features to it to fix the tangents, load the correct shader techniques, etc.
However XNA does not support loading animation data or gives you a way to display them. You have to do all that work by yourself. This includes static mesh animations (like it was used in Rocket Commander, I just left it out in Rocket Commander XNA), but also skeletal animation with bones and skinned meshes.

There is a nice project on CodePlex called XNA Animation Component Library, but it only support FBX and ASCII X files (and recently BVH, ASF and AMC formats) and I could not get any of my test models to work with this library. The main thing missing here is good shader support and it also has a lot of problems with complex animated models. Other than that exporting 3D Models as X files is really a pain in the ass, no matter which exporter you use (Panda Exporter for 3dsMax was good a year ago, I still use it, now kiloWatt X file Exporter for 3dsMax is better, and the Microsoft X File Exporter for Max always sucked). Simple models might work, but the more complex 3D models get and the more meshes and animation data is stored in a scene, the more problems you will have. Sometimes it is not possible to reconstruct everything correctly on your importer side.

Anyway, at the very beginning of the Racing Game development there was no content pipeline in XNA (it was Beta 1) and I implemented loading 3D Models with help of the collada file format, which is basically just XML and very easy to read. For that reason it was relatively simple to get some 3D data loaded and displayed in the early XNA versions with help of vertex buffers. There were some problems with shader settings and I had to try many different exporters and ended up with the one from Feeling Software. Back then it had still some problems loading shaders and using the correct techniques, but the recent version (3.0.2) is much better and works like a charm.

After Microsoft had implemented the content pipeline and made it possible to load X and FBX files indirectly by going over the content pipeline I had to remove most of my collada code and re implement the model loading with the new framework. Loading and displaying 3D models was much simpler this way and especially some early unit tests were really simple, but as soon I tried shaders and loading tangents there were a bunch of problems. I reported many bugs back then and it has gotten a lot better, but I still had to fix several issues in the Racing Game and Rocket Commander XNA myself like finding out the correct shader technique and fixing tangent data with help of a custom model processor.

Some things like the level loading in the Racing Game just do not work with X or FBX files because they use splines, which are not exported at all in these formats. Collada came as the rescue again because it is really no big problem for this format. Later versions of the Racing Game removed the collada level loading and introduced a binary format for the levels, but the importer still accepts collada files.

Recently I wanted to test a couple of animated models and use skinning since it can often be more useful than static animations and it usually looks much better, especially for organic 3D models. As I said above I could not get anything working with the XNA Animation Component Library and I especially do not like the way they still use the content pipeline and the project is too complicated for me anyway (I just do not need 6 different file formats, I just want one and it should work perfectly with all the features I need).

After some searching I saw some guy called remi from the collada forum was working on importing collada models too and I posted some thoughts there too (maybe this was a mistake, I got many emails asking me about tips ^^). Here is the thread about that in the collada forum. He has provided a test project with some models and it works nice for static meshes without shader information, but that was not really what I was searching for.

This was a month ago and I had not much time working on any of these issues, but after restarting my blog earlier this week I thought this would be a nice topic to talk about. I'm still pretty busy with Arena Wars Reloaded, but I worked a couple of hours every day on this little test program for the past few days. The rest of this article explains the project and into which problems I ran.

Class Overview

Before we go into the details here is a little class overview of the project. As I said before the Rocket Commander XNA engine was used to get up and running with the project without having to re implement the basics. Most of the classes were already in place and had not to be changed. ColladaModel and SkinnedTangentVertex are the 2 new classes and to help us out with the XML loading of the collada files the XmlHelper class was also brought into the project.

I wrote the ColladaModel file from scratch, but I could reuse some of the static mesh loading code I had done last year. All of the bone and animation loading code was just try and error and I only used the collada specifications as a source of help, but most stuff had to be tested with the unit tests at the end of the class many many times.

The main program just calls the unit tests TestGoblinColladaModelScene or TestShowBones, there is no real game here, its just a test program. The unit test then calls several Standard Engine classes for doing all the post screen processing, rendering the ground plane, etc. More importantly the ColladaModel class itself basically just provides a constructor and a Render method, everything else is private and will be handled automatically for you. Most people might ignore this, but this is always the most important thing about my classes, the use should be as simple as possible and when I look at the projects mentioned above I really ask myself why people sometimes think so complicated.

The internal Bone class inside ColladaModel is used to store all the bones in a flat list, but each entry has a parent and a list old children bones. This way the list can be used both in a simple for loop, but you can also go through it recursively (which is obviously slower and often more complicated). We will talk about the loading process in a minute.

All the mesh data is stored in vertices, which is just a list of SkinnedTangentVertex structs. The SkinnedTangentVertex struct is very much like the standard TangentVertex struct used in Rocket Commander XNA, but it has 2 new members: blendIndices and blendWeights. Both are in the form of Vector3 and their fore can hold 3 values allowing us to interpolate up to 3 bone influences for each vertex in the shader. More is often not required and we have to re normalize all bone weights anyway, so skipping the least important bone weights is not a big deal. My test models use mostly max. 2-3 influences. Please also note that the vertex shader has now a lot more work to do with all that skinning and you should really optimize it as much as possible. Both the number of vertices we have to process is important (we will talk about optimizing that in the optimizing part of this article) and also the number of instructions the vertex shader has, both numbers should be as low as possible. The GPU is really fast processing this data, but if you do not have animated geometry with bones, there is no reason to let it process all that data (which can make the vertex shader 2-3 times longer and slower). The ground of our test scene does not use a skinning shader as an example.

And finally there are some additions to the ShaderEffect class. First of all we got a new shader called "SkinnedNormalMapping", which does the same thing as the normal mapping (or parallax mapping) shader, but it has an array of 80 bone matrices we can use for skinning. These matrices are set with help of the SetBoneMatrices method in the Set Parameter region of ShaderEffect.cs.

Loading collada files

Before we go into the details of the loading process, lets make sure we read the summary of the class first because it clearly states what we can do and can't do with this class. This is just a test project and I wanted to make things as simple as possible for both you as the reader and for my requirements.

   /// <summary>
   /// Collada model. Supports bones and animation for collada (.dae) exported
   /// 3D Models from 3D Studio Max (8 or 9).
   /// This class is just for testing and it will only display one single mesh
   /// with bone and skinning support, the mesh also can only have one single
   /// material. Bones can be either in matrix mode or stored with transform
   /// and rotation values. SkinnedTangentVertex is used to store the vertices.
   /// </summary>
   class ColladaModel : IDisposable

OK, with that said let's go directly into the loading code, which is located in the constructor of this class. All variables used in these class are just for internal use, all you need to know are the vertices and bone lists, which I have already mentioned, and the vertex and index buffers, which are used for rendering. All the rest of the variables are just there to help us loading the collada file (don't worry, there are not many variables anyway and most methods are short too).

    #region Constructor
    /// <summary>
    /// Create a model from a collada file
    /// </summary>
    /// <param name="setName">Set name</param>
    public ColladaModel(string setName)
    {
        // Set name to identify this model and build the filename
        name = setName;
        string filename = Path.Combine(ColladaDirectory,
            StringHelper.ExtractFilename(name, true) + "." +
            ColladaExtension);

        // Load file
        Stream file = File.OpenRead(filename);
        string colladaXml = new StreamReader(file).ReadToEnd();
        XmlNode colladaFile = XmlHelper.LoadXmlFromText(colladaXml);

        // Load material (we only support one)
        LoadMaterial(colladaFile);
        
        // Load bones
        LoadBones(colladaFile);

        // Load mesh (vertices data, combine with bone weights)
        LoadMesh(colladaFile);

        // And finally load bone animation data
        LoadAnimation(colladaFile);

        // Close file, we are done.
        file.Close();
    } // ColladaModel(setFilename)