Preface

All units of measurement are in meters.

X axis (black)

The X axis is colored black in the picture. The range is from -2 to +2, where +2 is as close to the front screen as you can get. -2 is as far away from the front screen as you can get.

Y axis (blue)

The Y axis is colored blue in the picture. The range is from -2 to +2 where +2 is at the utter right side and -2 is to the left.

Z axis (red)

The Z axis is colored red in the picture. The range is from 0 to +3. 0 is as close to the ground as you can get.

Frames per second in Delta3D

I really wonder why this isn’t implemented in either Delta3D or OpenSceneGraph. Surely, I’m not the first guy who wishes to see how well my applications run on a particular system.

I eventually found a good forum post over at OpenSceneGraph describing what you need to do.

Frustum

I don’t think they like me. Or maybe I don’t like them. Possibly both. I see this as the last step in integrating the dt-cluster application with the existing CAVE-environment.

Maybe a brief explanation is needed. The head tracking system keeps track of your head’s position (!), and the trick is to then re-calculate the view frustum and update it.

So, with a huge amount of help from my professor and a bit of stubbornness, maybe I will manage.

Bugs, our best friends

I was able to squash one nasty bug that had bothered me for ages. Whenever joystick support was turned on, the result was a Blue Screen of Death. It was particularly hard to debug as all the information was lost due to an almost immediate restart.

After what felt like forever, I was able to narrow it down to one particular area (joystick support) and then the exact line of code. I still don’t know exactly what was wrong or why, but at least I found a work-around.

Added functionality

After not having to reboot the system every five minutes, implementing new features were suddenly much easier. I was able to add both initial support for the head tracking system and the 3D stereo separation. Of course, there are offsets in both cases that I have to identify to get it to work properly, but I am optimistic.

Unfortunately, it is the wrong kind of support that is offered per default.

dtInputISense.dll versus ISense.dll

InterSense provides two different .dll’s. The first one, dtInputISense.dll, provides joystick emulation for the head tracking system. When installed, it acts as a joystick; when you move your (in this case) head forward, the game will move forward.

This is probably quite adequate in most circumstances, but not in ours. We need the isense.dll, which is not provided in the Delta3D package, so we are forced to add it as a dependency.

The one used in the dt-cluster project is: InterSense DLL Version 4.08 (32-bit/x86 Windows).

Slashdot posted an article that the Unreal Engine 3 is now free to use. Could this be interesting for our project?

“Just a week after Unity announced its engine is now available for free to indie users, Epic Games has revealed a free version of its popular Unreal Engine technology. Called the Unreal Development Kit (UDK), it is a free edition of UE3 that allows community, modder and indie users more access to the engine’s features and is available for all. Epic said game developers, students, hobbyists, researchers, creators of 3D visualizations and simulations plus digital filmmakers can all take advantage of the UDK for non-commercial use. The UDK site also offers detailed product features, technical documentation, commercial licensing terms and support resources.”

Quoted from Slashdot.

Differences

With the free license, you do not get access to the C++ source code. Epic Games also state that UDK ships with “most of the same code and tool integrations as the commercial version”.

Another thing that is worth pointing out is that if you intend to use the UDK for any commercial purpose, it is no longer free of charge.

Benefits

Unreal Engine 3 is considered to be a current generation game engine (Q4 2009). It has also been used in a variety of high profile games:

• Unreal Tournament 3
• Gears of War
• Gears of War 2
• Mortal Kombat vs. DC Universe

Skeletal Animation

UDK supports Skeletal Animation.

Parallel rendering

UDK has extensive networking support, which probably would allow you to implement a distributed rendering cluster.

3D Studio Max

The UDK kit includes ActorX, which is Unreal Engine 3’s mesh and animation exporter ActorX for 3D Studio Max, Maya, and XSI.

It supports the following versions of 3D Studio Max

3ds Max 2010 (32-bit)
3ds Max 2010 (64-bit)
3ds Max 2009 (32-bit)
3ds Max 2009 (64-bit)
3ds Max 2008 (32-bit)
3ds Max 2008 (64-bit)
3ds Max 9 (32-bit)
3ds Max 9 (64-bit)
3ds Max 8
3ds Max 7
3ds Max 6, CStudio 4.2
3ds Max 5.0,5.1, CStudio 3.4 & 4.0
3ds Max 4.2, CStudio 3.2
3ds Max 4, CStudio 3.x
3ds Max 3.1, CStudio 2.2
3ds Max 3.1, CStudio 3.0 ( update 1.99h )
3ds Max 3.1, CStudio 3.0

Documentation

There seems to be extensive documentation which is maintained by Epic Games and it is located here.

Background

My tutor had previously written a clustering client-server application that utilizes GNE to talk to the nodes. It works well under version 2.2.0. After some frustrating hours, it now works under 2.4.0-RC2 aswell.

The underlying reason was that Delta3D’s scene graph, OpenSceneGraph, had changed. More specifically, the OSGViewer::View class.

• Delta3D 2.2.0 uses OpenSceneGraph 2.6.1 (documentation)
• Delta3D 2.3.0 uses OpenSceneGraph 2.8.0 (documentation)
• Delta3D 2.4.0 uses OpenSceneGraph 2.8.2 (documentation)

What has been tested

The test consists of one server application and four client applications. The test was conducted on one PC, and the server-client communication was via the static loopback address of 127.0.0.1.

A test has also been conducted where a server runs one application and one client runs another. The two computers are connected together via an Ethernet LAN. The test turned out successfully.

What needs further testing

Setting it up in a CAVE-like environment and evaluating its performance.

Source code

The source code is hosted by Google Code and made available under the MIT License.

What do I need?

Before I start, I think it makes sense to state what needs I have.

The primary goal is to bring an open source visualization solution to a CAVE-like environment located in Lund, Sweden. This is because our current system doesn’t allow us to visualize human beings, which we want to accomplish with Skeletal animation.

The visualization solution must be able to provide support for

• A variety of input controllers
• Head tracking
• Stereoscopic rendering
• Windows XP
• Clustering / Parallel rendering via Ethernet
• Skeletal animation
• Audio
• Physics & collision detection

3D rendering engine

Definition

A 3D rendering engine’s main purpose is to provide a general solution for graphics rendering by giving the programmer an abstraction layer to the underlying system libraries, e.g. OpenGL, Direct3D.

Pros

Freedom. You can choose whatever other libraries you want, and you can restrict them to contain only the ones that you need.

Cons

You yourself have to make every different part of your ad-hoc game engine work. That could mean that you spend a lot of time just making the different subsystems talk to each other.

Game engine

Definition

A game engine consists of all the things you need to build a game. That is, most notably, a 3D rendering engine, sound, networking, AI, collision, physics etc.

Pros

When everything is bundled together like they are in a game engine, it makes the job easier for me, the developer. I can therefore spend my time with coding the actual application.

Cons

By design, you are more restricted using a game engine. If you want to make your own life easy, you more or less have to stick with the various tools that are in that particular game engine.

Discussion

There seems to be less trouble involved with picking a game engine over a 3D rendering engine. You get all the libraries you will need and in the best of worlds: it just works.

However, I have been eyeing a 3D rendering engine that seems to be quite capable. That said, it might be interesting to try and see how long it takes to get various subsystems integrated.

Ogre seems to grow more and more on me the more I look into it.

Parallel rendering

Parallel rendering in Ogre3D has been known to work in a cluster of PC:s. There is even an extensive guide on the wiki on how to set up a cluster using Ogre3D, Chromium and DMX.

Head tracking

Ogre3D has a howto on how to set up head tracking with a wWii remote, just as Johnny Lee did.

Interoperability

This could be a potential problem. The virtual reality software that we run right now, E-ON Studio, runs om Windows XP. It would therefore be practical if the open source solution that is to be implemented would co-exist on that particular operating system. However, most documentation seem to be aimed at the Linux environment. This applies to the Parallel rendering example in particular, as it uses DMX X servers, which are not available in a Windows environment.

Granted, there are builds for Windows XP. However, doubt remain as to whether I in Windows can do e.g. parallel rendering.

Downside

Ogre3D is not a game engine. It is only a scene graph so if you want audio, physics etc (like we do) you would have to include those libraries yourself. This could lead to that you put way too much effort in just getting all the different pieces of the “game engine” to work with each other. Time that you could have spent developing.

How it was done

The CaveUT project solved the problem of rendering different screens by utilizing UT2004’s spectator mode. The game allows a maximum of 32 players, and as such your maximum number of view nodes are limited to 32.

More information can be found here.

Licensing

UT2004’s game engine, Unreal Engine, is not licensed under open source. However, there seems to be a free, educational license called Unreal Engine 2 Runtime: Demo Version. If that is enough for our needs is unclear. Further research is needed.

Usage

ioquake3 is released under the GPLv2 license, and a number of games have been released using this engine. A more detailed list which also includes products using the proprietary license is located here.

Additional comments

id’s next iteration of their game engine, tech 4, is expected to be released under the GPL license in 2010.

Skeletal animation

ioquake3 doesn’t have skeletal animation in its true sense. Instead, it relies on MD3 meshes. The animations contained in an MD3-file are vertex based.

This can be seen as a draw-back compared to skeletal animation, and is worth pointing out.

Benefits

ioquake3 along with id’s tech 3 have proven to be a reliable, high-performance game engine.

Bottom line

ioquake3 lacks support for Skeletal Animation. Therefore, it is not suitable for our work, although it has some very nice benefits.