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The XL Engine is and will remain free, donations are purely optional but greatly appreciated.

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Archive for February 2013

Motivation

In the past I talked about the terrain system as seen in the current release of DaggerXL. For the Beta, the terrain on older hardware will be done in a similar way, though with the enhancements as shown in the last video – improved coastlines, animated water, proper ground texture usage, etc.. In this post I will be talking about the system I hinted at in the Continuing and OpenGL Support post – “This renderer will feature view distances of greater then 100km as well as the highest quality rendering.”

So you might be wondering, why bother extending the rendering distance so far when emulating an old game like this? To answer that we’ll have to think about more modern Elder Scrolls games – Morrowind, Oblivion, Skyrim. The view distances in those games aren’t much bigger then the current version of DaggerXL, smaller in some cases. Yet the terrain has more variety and interesting features. Why is that? To put it simply, these games – like many games – are like themeparks, packing all the interesting locations together and removing or drastically reducing the space in-between. In just a few hundred meters you can see entire biomes, an arduous climb up the tallest mountain takes minutes rather then hours or days. This allows these games to pack a lot of interest and variety into a relatively small view distance. Unfortunately this can also result in obvious absurdity if the designers aren’t careful – like tripping over ancient hidden ruins constantly in Oblivion.

Daggerfall uses a realistic scale for terrain which has many benefits such as making the world feel much larger and more authentic. Unfortunately it trades the “themepark” feel for an environment that feels homogeneous and boring. One of the reasons is that the interesting features are spread over a much larger scale – so the proper thing to do is extend the view to realistic distances as well, this way one can appreciate the large scale vistas currently hidden in the fog. It is obvious why this couldn’t be done when Daggerfall came out on DOS and of course the amount of the view distance can be extended on older hardware is limited – though still a significant improvement. But with modern hardware there is no good reason that we can’t extend the view distance to realistic levels now.

 

Beyond the Map

But wait! What happens when you look over the edge of the Daggerfall map? With the previous DaggerXL view distances, stretching the height map and adding in procedural details was enough to be convincing – which I actually implemented, see the Terrain Beyond the Map Borders post. However when using realistic view distances this obviously doesn’t work and looks downright silly. I considered other options, such as shrouding the edges in thick fog – which is something that is oftentimes done to artistically hide the edges of a limited map

(example Zelda map from http://www.zeldacapital.com – note this has no relation to this project, just a nice picture to illustrate the idea, though I am a big Zelda fan too)

 

However this would still result in really odd visuals and give the impression that the Daggerfall area is shrouded and cutoff from the rest of Tamriel – which was not Bethesda’s original intent. So I decided on a new approach, with the help of suggestions from some others.

 

Tamriel

So what is beyond the edges of the Daggerfall map? The rest of Tamriel of course. :D  So what I’ve decided to do is to put together a heightmap of Tamriel – at the same scale as Daggerfall – and fit it to the Daggerfall data. Below is a screenshot of that map, though still unfinished –

[img removed]

The actual height map is over 5000 pixels in width, where each pixel is the same size as the pixels in Daggerfall’s 1000×500 heightmap. Daggerfall is inserted into the correct place, with the rest of the world rotated and scaled to fit. I consider the Daggerfall data to be ‘correct’ since this is for DaggerXL after all, so the Daggerfall data will still be pulled from the original data files, I inserted it into this map so I can fit the map to it rather then the other way around. There are several issues with this map still, I have to fix up coastlines and the Black Marsh area and fit the map to a 500×500 pixel grid, so that Daggerfall takes up exactly 2 grid cells. If you can see off the edge, it’ll wrap to the other side – same for swimming, flying or sailing across an edge. This way only 9 heightmap cells need to be in memory at once in order to render the world. Of course, for now, only the area from Daggerfall will have locations. However part of the intent of this is that you guys will have the rest of Tamriel already available when the modding tools come online. Don’t like parts of the heightmap – you can edit the file and distribute it. If you guys, as a community, come up with the definitive heightmap and it works with the existing Daggerfall data – then I’ll replace this map with that one in the future DaggerXL releases.

That said wait until you get the final heightmap before doing anything with it. It will have to conform to the grid, which this one does not yet. Also there is a seperate map, not shown here, that contains data such as the proper terrain textures to use.

 

In Part 2, which should come out next week, I’ll show the terrain system in action and talk about how it actually works under the hood.

In the last post, I talked a little about how OpenGL support is going to work and about extending the support to include Fixed Function and even software rendering (though that will come online a little later). In this post I will start a little about the architecture of the XL Engine and how supporting different games has been implemented.

The main XL_Engine executable contains the core engine, it contains all the platform specific code, OpenGL and other core systems (sound system, scripting engine, networking layer, etc.).

The engine also contains an “Archive” system, which transparently allows file handling code to lookup and read files from many Archive file formats – such as GOB, LAB, BSA, ART and so on. Then for files that perform specific functions – say image/texture files or level/location/chunk data – the system can transparently load the appropriate data and have it converted internally to the correct format based on the current settings and type. For example, when using the Software renderer 8 bit images are kept in that format but are converted to 32 bit as needed, based on the current palette and color map, for the OpenGL renderer. Currently the file format data is all internal but it is also possible to write Dynamic Library based plugins, similar to the way different games are supported (DLL/so).

Game code is implemented as plugins,  each game consists of a game library (DLL/so), script files and any game specific assets (in the case of games like DaggerXL – these assets are things like icons, title screen, etc.). In addition there is a small text file that describes the game so that it can be added to the list of games in the launcher. The engine has a dynamic library handler that supports Windows, Linux and OS X – there is very little code difference between systems and it is all handled by the Plugin system built into the engine. So for game and plugin code, the engine is used to handle all the OS and engine work – including things like input, file handling, script engine and so forth – allowing the game code to be platform agnostic. Obviously the same is true for all the scripts written as well.

Game plugins register various callbacks with the engine – so that they can receive input, start up game flow and UI scripts, handle pre and post render events, update and handle other events. The game will setup console functions (and potentially variables) and script functions, create entities and register game specific “logics.” Logics are self-contained functional elements, written in code or script, that make objects do things. As an example, a “Door” logic will cause a door to open or close when it receives and activation message. An entity is controlled by one or more of these logics, which are either assigned by the game code itself, through scripts or from the level data. Entities are handled by the core engine but Logics allow them to be controlled from game code, scripts and even shared logics built into the engine.

Anyway, this description just scratches the surface – there is plenty more to talk about in future posts, such as threading model, resource loading, virtual processes allowing for multiple plugins to run simultaneously (such as the editor and one or more games), networking model, script based game flow, script based UI and more. Stay tuned for future posts. :)

First I apologize for making a promise that I couldn’t keep. However I still believe Beta is within the original time frame I estimated but other things got in the way, as usual. Anyway, enough about that.

The goal is still the same, the next release will be the Beta release for DaggerXL. Everything is up and running again and I’ve started to get back to the project, which is coming along fairly well. The next release will still be the Beta – which means NPCs, quests, dialog, shopping, spells, guilds and so forth. Later I’ll talk about progress on the game and such but first I’ll talk a bit about support plans.

The Linux version will not be coming out with the Beta. While the engine supports Linux now, my new computer does not… Well its a long story but suffice it to say that I have issues to work out before development on the Linux version can continue. This is something I’m planning on doing but I’m not going to delay the next release any more then I already have because of it.

I’m shelving the software renderer for the next release and am going to focus on the OpenGL side of things for this release to save a little time. The software renderer will become available with the following release instead so it won’t be shelved for long. However, for those with older systems, I will still be supported fixed function hardware with a reduced feature set. Below I’ll list the major OpenGL versions that will be supported:

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* OpengGL 1.2 - simple renderer with single textures and basic OpenGL fog. In terms of lighting this will be the least faithful renderer compared to the “vanilla” game – but there is only so much that can be done without shaders or multi-texture support. Only the first terrain LOD will be available, limiting the view distance to the same range as supported by the software renderer (see the last video to get an idea how far that is). You’ll be able to decrease the view distance to get performance on really old systems. This mode should support GPUs all the way back to the GeForce 256, released in 1999. Intel Integrated graphics should be fully supported from 1999 on (as well as other integrated chipsets that support OpenGL).

* OpenGL 1.5 - this is basically the same as the above but adding support for multi-texture and Vertex Buffer Objects. This will allow for faster rendering and slightly better lighting but will otherwise be the same as above. GPUs made in 2003 or newer should be able to use this mode.

* OpenGL 2.1 - this adds shader support, which will allow the lighting and fogging to look close to the original. Effects like Bloom will be available as well. Cards from 2005 and newer should support this mode. [for NVidia owners: GeForce 6000 series or newer]

* OpenGL 3.1 - this will be the “fully featured” renderer. This renderer will feature view distances of greater then 100km as well as the highest quality rendering. GPUs made in 2007/2008 and later (depending on brand) should support this mode. So if you have a discrete GPU and bought your computer in the last couple of years, you should be able to enjoy the game with maximum quality. [for NVidia owners: GeForce 8000 series or newer]

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If you have any concerns or questions about support for your GPU or computer, please let me know. Unfortunately I cannot guarantee performance on really old systems but I can at least make sure the XL Engine runs and have settings you can turn down to help eek out the performance you need. :) In previous builds many people had performance issues in areas with lots of lights or foliage – that should no longer be the case with the Beta.

 

The XL Engine is and will remain free, donations are purely optional but greatly appreciated.