Build engine

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Build Engine

Looking down in the Duke Nukem 3D level Raw Meat, notice the lines of the walls are perfectly vertical.
Developer: Ken Silverman
Use: Game Engine
Website: http://advsys.net/ken/build.htm

The Build engine is a first-person shooter engine created by Ken Silverman for 3D Realms. Like Doom, the Build engine represents its world on a two-dimensional grid using closed 2D shapes called sectors, and uses simple flat objects called sprites to populate the world geometry with objects. It is generally considered to be a 2.5D engine as the basic world geometry is two-dimensional with an added height component as each sector may have a different ceiling and floor height, and the ceiling and floor may be angled along one line of the sector. The engine renders the world in a way that looks three-dimensional. However the sizing for perspective only depends on the horizontal distance (most noticeable as the fact that wall vertices are always straight vertical lines on screen). This can cause noticeable distortion when looking up and down and so most Build games restrict this to a fairly limited range of angles.

Contents

[edit] Technical features

[edit] Sectors

The Build engine allowed for more complex and flexible worlds than Doom by virtue of its representation of the world information. Sectors could be manipulated in real-time; their shape, heights, and slope angles being completely variable, without requiring recalculation of rendering information. This allowed games to have destructible environments, such as those seen in Blood.

Developers of games based on the engine used reserved sprites, often called sector effectors, that when given special tags (numbers with defined meanings), would allow the level designer to make a dynamic world that appeared to be 3D. Similar tag information could be given to the sector walls and floor area to give a sector special characteristics. For example, a particular sector effector may let a player fall through the floor if he walked over it and teleport him to another sector. In practice, this could be used to create the effect of falling down a hole to a bigger room or creating a body of water that could be jumped into to explore underwater. A sector could be given a tag that made it behave like a simple elevator or lift. Sectors could overlap one another provided they could not be seen at the same time (if two overlapping sectors were seen at the same time a corrupted display resulted). This allowed the designers to create, for instance, air ducts that appeared to extend across the top of another room (however doing so could be tricky for designers due to the 2D viewpoint used for much of the editing process). More interestingly, this allowed the designer to create worlds that would be physically impossible (e.g. a door way of a small building could lead into a network of rooms that was larger than the building itself). While all these things made the game appear to be 3D, it wouldn't be until later first-person shooters, like Quake, that the engine actually stored the world geometry as true 3D information.

[edit] Voxels

Later versions of Ken's Build engine allowed game selected art tiles to be replaced by 3D objects made of voxels. This feature appeared too late to be used in Duke Nukem 3D but was seen in several of the later Build engine games. Blood uses voxels for weapon and ammo pickups, powerups, and occasionally eye-candy (such as the tombstones in the Cradle to Grave level). Shadow Warrior makes even more advanced use of the technology, with voxels that can be placed on walls (all of the game's switches and buttons are voxels) and even a rudimentary 3D enemy mode that can be toggled via the F5 key, and replaces all of the game's enemy sprites with voxels. This is extremely buggy, and seems to be little more than an unfinished test mode.

For several years Ken has been working on a modern engine based entirely on voxels, known as Voxlap.

[edit] Room over room

Several Build engine games used a trick involving rendering multiple times to draw two sectors that were joined floor to ceiling. As building the sectors over top of each other was not really feasible due to limitations of the editor, the sectors could either be moved at map load time (which made calculations during the game simpler), or left where they were. The two best known games to use this trick were Shadow Warrior (which moved the sectors at map load time) and Blood (which did not). This trick was not a feature of the Build engine but rather a trick that was discovered by game developers.

[edit] Build engine games

Duke Nukem 3D is the most famous Build engine game.
Duke Nukem 3D is the most famous Build engine game.

Though the Build engine achieved most of its fame as a result of powering the classic first person shooter Duke Nukem 3D, it was used for many other games.

[edit] Source release and further developments

On June 20, 2000 (according to his website) Ken released the Build engine source code.

[edit] The early days

Version 2.0 (the first and only official binary release) of Matt Saettler's Eduke (a project to improve duke nukem 3D for modders) was sent to 3D Realms for packaging (both Duke nukem 3D and EDuke were still closed source at this point) only just after the release of the build source and hence stuck with the build libraries that 3D realms had used in the original duke.

With the 2.1 private Betas Matt worked towards integrating kens build source into the duke source but the project fizzled out before producing anything more than some very buggy private betas. A few total conversion teams for Build games decided to work from Ken's Build code directly and an enhanced version of the Build editor known as mapster was also developed.

It was claimed at the time by many on the 3D Realms forums that it would be impossible to port Build to a multitasking OS as it needed a large contiguous block of memory that wouldn't be available in a multi tasking environment. This statement doesn't hold up to scrutiny as all modern operating systems use virtual memory which allows apps to get contiguous logical memory without using contiguous physical memory but nonetheless remained widely believed for quite some time.

[edit] The Duke Nukem 3D source release

On April 1, 2003 3D Realms released the source code to Duke Nukem 3D after years of saying it would never happen. Not long afterwards both Icculus and JonoF had ports made. It was now possible to play Duke Nukem 3D well on the NT line of Windows (including Windows 2000/XP) and interest in the ports soared.

[edit] The icculus.org port

Ryan C. Gordon (icculus) with the help of others made the first port of the engine using SDL. The port was first to Linux, then to Cygwin and finally to a native Windows build using the Watcom C++ compiler, which was the compiler used for the original DOS build (despite being compiled with Watcom C++, Build is plain C). There was some talk of Matt Saettler using this to port Eduke to Windows but nothing came of it.

[edit] The JonoF port

A second port was made to Windows and later Linux by Jonathon Fowler (JonoF). Unlike the icculus port, this used DirectDraw rather than SDL on Windows and was generally faster. However it didn't have network game support until much later and when network support finally did arrive for a long time it only worked with two players.

[edit] Polymost

Looking down in the Duke Nukem 3D level Raw Meat in polymost mode, the true 3D perspective is apparent. Note that the corners of the walls are no longer exactly vertical.
Looking down in the Duke Nukem 3D level Raw Meat in polymost mode, the true 3D perspective is apparent. Note that the corners of the walls are no longer exactly vertical.

The task of updating the Build engine to a true 3D renderer was taken on by the author of the engine. In the release notes for JFDuke3D, Silverman writes:

When 3D Realms released the Duke Nukem 3D source code, I thought somebody would do a OpenGL or Direct3D port. Well, after a few months passed, I saw no sign of somebody working on a true hardware-accelerated port of Build, just people saying it wasn't possible. Eventually, I realized the only way this was going to happen was for me to do it myself.

The Polymost renderer allows for 3D hardware accelerated graphics using OpenGL. It also introduced "hightile," a feature that made it possible to replace the game's original textures with high-resolution replacements in a variety of formats.

Polymost has been utilized in Jonathon Fowler's JFBuild, JFDuke3D, JFSW, and ports derived from their codebases.

[edit] Other ports

Source for Eduke 2.0 was released but it took a while due to the fact that some people had problems compiling the archived source. This was merged with the JonoF port of Duke Nukem 3D, and many features from 2.1 and various other eduke branches were added by TerminX to make Eduke32. wineduke has since died off leaving Eduke32 the only Eduke port still in development.

Source for the last private beta of Eduke 2.1 (which never made it to a release version) was also released soon after the EDuke 2.0 source. There was a port of this based on the ICCULUS code known as wineduke, but those working on it became frustrated with bugs still in the pre-Alpha 2.1 source.

Eduke contained the code from Nam and WW2 GI so these could probably be made to work with it without too much effort, but there do not seem to be any projects that do so currently. There has also been the Transfusion project which aimed to re-create Blood in the DarkPlaces engine, but as of 2006, this is far from complete.

The Shadow Warrior source was released on April 1, 2005. And JonoF released a port of it on April 2, 2005. However, he admitted that he had access to the Shadow Warrior source about a week before its release.

The source code of Witchaven, Witchaven II, Tekwar and Corridor 8 are also released. The legal status of these releases is however somewhat unclear.

[edit] External links

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