Entities Spawned by QuakeC Code

Thursday, 6th September 2007

After all that time spent trying to work out how the QuakeC VM works I finally have some real-world results. smile.gif

Apart from the obvious boring stuff going on in the background parsing and loading entities go, two functions in particular are of note. The first is a native function, precache_model(string) which loads and caches a model of some description (sprites, Alias models or BSP models). The QuakeC VM I've written raises an event (passing an event containing the name of the model to load), which the XNA project can interpret and use to load a model into a format it's happy with.

Inspiration for the Strogg in Quake 2?

With a suitable event handler and quick-and-dirty model renderer in place, the above models are precached (though they probably shouldn't be drawn at {0, 0, 0}).

The second function of interest is another native one, makestatic(entity). Quake supports three basic types of entity - dynamic entities (referenced by an index, move around and can be interacted with - ammo boxes, monsters and so on), temporary entities (removes itself from the game world automatically - point sprites) and static entities. Static entities are the easiest to handle - once spawned they stay fixed in one position, and can't be accessed (and hence can't be removed). Level decorations such as flaming torches are static. Here's the QuakeC code used to spawn a static small yellow flame:

void() light_flame_small_yellow =
	precache_model ("progs/flame2.mdl");
	setmodel (self, "progs/flame2.mdl");
	FireAmbient ();
	makestatic (self);
That ensures that the model file is precached (and loaded), assigns the model to itself, spawns an ambient sound (via the FireAmbient() QuakeC function) then calls makestatic() which spawns a static entity then deletes the source entity. In my case this triggers an event that can be picked up by the XNA project:

// Handle precache models:
void Progs_PrecacheModelRequested(object sender, Quake.Files.QuakeC.PrecacheFileRequestedEventArgs e) {
	switch (Path.GetExtension(e.Filename)) { 
		case ".mdl":
			if (CachedModels.ContainsKey(e.Filename)) return; // Already cached.
			CachedModels.Add(e.Filename, new Renderer.ModelRenderer(this.Resources.LoadObject<Quake.Files.Model>(e.Filename)));
		case ".bsp":
			if (CachedLevels.ContainsKey(e.Filename)) return; // Already cached.
			CachedLevels.Add(e.Filename, new Renderer.BspRenderer(this.Resources.LoadObject<Quake.Files.Level>(e.Filename)));

// Spawn static entities:
void Progs_SpawnStaticEntity(object sender, Quake.Files.QuakeC.SpawnStaticEntityEventArgs e) {
	// Grab the model name from the entity.
	string Model = e.Entity.Properties["model"].String;

	// Get the requisite renderer:
	Renderer.ModelRenderer Renderer;
	if (!CachedModels.TryGetValue(Model, out Renderer)) throw new InvalidOperationException("Model " + Model + " not cached.");

	// Add the entity's position to the renderer:
	Renderer.EntityPositions.Add(new Renderer.EntityPosition(e.Entity.Properties["origin"].Vector, e.Entity.Properties["angles"].Vector));

The result is a light sprinkling of static entities throughout the level.


As a temporary hack I just iterate over the entities, checking if each one is still active, and if so lumping them with the static entities.


If you look back a few weeks you'd notice that I already had a lot of this done. In the past, however, I was simply using a hard-coded entity name to model table and dumping entities any old how through the level. By parsing and executing progs.dat I don't have to hard-code anything, can animate models correctly, and even have the possibility of running the original game logic.

An example of how useful this is relates to level keys. In some levels you need one or two keys to get to the exit. Rather than use the same keys for each level, or use many different entity classes for keys, the worldspawn entity is assigned a type (Mediaeval, Metal or Base) and the matching key model is set automatically by the key spawning QuakeC function:

/*QUAKED item_key2 (0 .5 .8) (-16 -16 -24) (16 16 32)
GOLD key
In order for keys to work
you MUST set your maps
worldtype to one of the
0: medieval
1: metal
2: base

void() item_key2 =
	if (world.worldtype == 0)
		precache_model ("progs/w_g_key.mdl");
		setmodel (self, "progs/w_g_key.mdl");
		self.netname = "gold key";
	if (world.worldtype == 1)
		precache_model ("progs/m_g_key.mdl");
		setmodel (self, "progs/m_g_key.mdl");
		self.netname = "gold runekey";
	if (world.worldtype == 2)
		precache_model2 ("progs/b_g_key.mdl");
		setmodel (self, "progs/b_g_key.mdl");
		self.netname = "gold keycard";
	self.touch = key_touch;
	self.items = IT_KEY2;
	setsize (self, '-16 -16 -24', '16 16 32');
	StartItem ();
Mediaeval Key
Metal Runekey
Base Keycard

One problem is entities that appear at different skill levels. Generally higher skill levels have more monsters, but there are other level design concerns such as swapping a strong enemy for a weaker one in the easy skill mode. In deathmatch mode entities are also changed - keys are swapped for weapons, for example. At least monsters are kind - their spawn function checks the deathmatch global and they remove themselves automatically, so adding the (C#) line Progs.Globals["deathmatch"].Value.Boolean = true; flushes them out nicely.

Each entity, however, has a simple field attached - spawnflags - that can have bits set to inhibit the entity from spawning at the three different skill levels.


Regrettably, whilst the Quake 1 QuakeC interpreter source code is peppered with references to Quake 2 it would appear that Quake 2 used native code rather than QuakeC to provide gameplay logic, so I've dropped development on the Quake 2 side at the moment.


Monday, 3rd September 2007

This journal hasn't been updated for a while, I know. That doesn't mean that work on the Quake project has dried up - on the contrary, a fair amount of head-way has been made!


The problem is that screenshots like the above are really not very interesting at all. rolleyes.gif

As far as I can tell, Quake's entity data (at runtime) is stored in a different chunk of memory to the memory used for global variables. I've had numerous problems getting the code to work - most of which caused by pointer confusion. Four bytes are generally used for a field (vectors use three singles, so you have 12 bytes), so I've tried multiplying and dividing offsets by four to try and get it all to work.

The basic entity data is stored in the .bsp file. It takes the following form:

"worldtype" "2"
"sounds" "6"
"classname" "worldspawn"
"wad" "gfx/base.wad"
"message" "the Slipgate Complex"
"classname" "info_player_start"
"origin" "480 -352 88"
"angle" "90"
"classname" "light"
"origin" "480 96 168"
"light" "250"

classname describes the type of the entity, and the other key-value pairs are used to adjust the entity's properties. All entities share the same set of fields, which are declared in a special section of the progs.dat file.

For each classname there is a matching QuakeC function. As far as I can tell the trick is to decode an entity then invoke its QuakeC method.

void() light =
	if (!self.targetname)
	{	// inert light

	if (self.style >= 32)
		self.use = light_use;
		if (self.spawnflags & START_OFF)
			lightstyle(self.style, "a");
			lightstyle(self.style, "m");

As you can probably guess, if a light entity is not attached to a particular target it is automatically removed from the world as it serves no useful function (the lightmaps are prerendered, after all). A similar example comes from the monsters which remove themselves if deathmatch is set. The QuakeC code also contains instructions on setting which model file to use for each entity and declares the animation frame sequences, so is pretty important to get working. smile.gif

I have a variety of directories stuffed with images on my website, and (thankfully) I have used a faintly sane naming convention for some of these. I knocked together a PHP script which reads the files from these directories and creates a nifty sort of gallery. It automatically generates thumbnails and is quite fast. As I don't have an internet connection at home it's more practical to be able to just drop files into a directory and have the thing automatically update rather than spend time updating a database.

PHP source code (requires GD).

It's INI file driven. The two files are config.ini:

base_dir=../../ ; Base directory of the site
; I put this in bin/gallery, so need to go up two levels :)

valid_extensions=jpg,gif,png ; Only three that are supported

quality=90 ; Thumbnail JPEG quality

...and galleries.ini:

[VB6 Terrain]
key=te                 ; Used in gallery=xyz parameter
path=projects/te       ; Image location, relative to base_dir
date_format=ddmmyyyyi  ; Filename format, where i = index.

ignore_extensions=jpg     ; Can be used to ignore extensions.

The index in the date format is for files that fall on the same date. Historically I used a single letter (01012003a, 01012003b), currently I use a two-digit integer (2003.01.01.01).

If a text file with the name of the image + ".txt" is found, that is used as a caption. (eg, /images/quake/2003.01.01.01.png and /images/quake/2003.01.01.01.png.txt).

It's not designed to be bullet-proof (and was written very very quickly) but someone might find it a useful base to work on. smile.gif

QuakeC VM

Wednesday, 15th August 2007

I've started serious work on the QuakeC virtual machine.


The bytecode is stored in a single file, progs.dat. It is made up of a number of different sections:

  • Definitions data - an unformatted block of data containing a mixture of floating point values, integers and vectors.
  • Statements - individual instructions, each made up of four short integers. Each statement has an operation code and up to three arguments. These arguments are typically pointers into the definitions data block.
  • Functions - these provide a function name, a source file name, storage requirements for local variables and the address of the first statement.

On top of that are two tables that break down the definitions table into global and field variables (as far as I'm aware this is only used to print "nice" names for variables when debugging, as it just attaches a type and name to each definition) and a string table.

The first few values in the definition data table are used for predefined values, such as function parameters and return value storage.

Now, a slight problem is how to handle these variables. My initial solution was to read and write types strictly as particular types using the definitions table, but this idea got scrapped when I realised that the QuakeC bytecode uses the vector store opcode to copy string pointers, and a vector isn't much use when you need to print a string.

I now use a special VariablePointer class that internally stores the pointer inside the definition data block, and provides properties for reading and writing using the different formats.

/// <summary>Defines a variable.</summary>
public class VariablePointer {

	private readonly uint Offset;

	private readonly QuakeC Source;

	private void SetStreamPos() { this.Source.DefinitionsDataReader.BaseStream.Seek(this.Offset, SeekOrigin.Begin); }

	public VariablePointer(QuakeC source, uint offset) {
		this.Source = source;
		this.Offset = offset;

	#region Read/Write Properties

	/// <summary>Gets or sets a floating-point value.</summary>
	public float Float {
		get { this.SetStreamPos(); return this.Source.DefinitionsDataReader.ReadSingle(); }
		set { this.SetStreamPos(); this.Source.DefinitionsDataWriter.Write(value); }

	/// <summary>Gets or sets an integer value.</summary>
	public int Integer {
		get { this.SetStreamPos(); return this.Source.DefinitionsDataReader.ReadInt32(); }
		set { this.SetStreamPos(); this.Source.DefinitionsDataWriter.Write(value); }

	/// <summary>Gets or sets a vector value.</summary>
	public Vector3 Vector {
		get { this.SetStreamPos(); return new Vector3(this.Source.DefinitionsDataReader.BaseStream); }
		set {


	#region Extended Properties

	public bool Boolean {
		get { return this.Float != 0f; }
		set { this.Float = value ? 1f : 0f; }


	#region Read-Only Properties

	/// <summary>Gets a string value.</summary>
	public string String {
		get { return this.Source.GetString((uint)this.Integer);  }

	public Function Function {
		get { return this.Source.Functions[this.Integer]; }


Not too elegant, but it works!

If the offset for a statement is negative in a function, that means that the function being called is an internally-implemented one. The source code for the test application in the screenshot at the top of this entry is as follows:

float testVal;

void() test = {
	dprint("This is a QuakeC VM test...\n");
	testVal = 100;
	dprint(ftos(testVal * 10));
	while (testVal > 0) {
		testVal = testVal - 1;
	dprint("Lift off!");

Both dprint and ftos are internal functions; I use a simple array of delegates to reference them.

There's a huge amount of work to be done here, especially when it comes to entities (not something I've looked at at all). All I can say is that I'm very thankful that the .qc source code is available and the DOS compiler runs happily under Windows - they're going to be handy for testing.

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