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# A. Glossary

This is a short glossary of terminology used throughout the documentation as well as in discussions of 3D graphics.

3D Renderer

  The 3D renderer plugin in Crystal Space is responsible for rendering 3D objects (polygons) on the canvas. We have several renderers but the two most common are the software and OpenGL renderers.

3D Sprite

  A 3D Sprite in Crystal Space is a mesh object based on a triangle mesh. It is often used for actors. The word ``Sprite'` may be confusing because a 3D Sprite is really a full 3D object. 3D Sprites support frame based animation. The SPRCAL3D mesh object also supports skeletal animation through the Cal3d library.

Ambient (lighting)

  Ambient lighting is a constant amount of lighting that is added to all other lighting.

Camera Space

  Before viewing objects and rooms are transformed from world to camera space. This means that the position of the camera is set at (0,0,0); the positive z direction points away from the eyes, the y direction is up and the x direction is right.

Canvas

  A canvas is a plugin which is responsible for managing a window for Crystal Space. On operating systems that don't support windows the canvas will represent the screen. The 3D renderer will use a canvas to render on.

Detail Texture

  A detail texture is a texture that is blended on top of another texture so that the texture gets more detail. Crystal Space supports this by allowing several detail layers on top of the base texture in a material.

Event Queue

  Crystal Space is an event-driven framework. So a Crystal Space application will also be event driven. The event queue manages the event system and sends events to listeners. Every module or plugin that implements `iEventHandler` can register itself with the event queue so it gets notified when certain events happen. See also with `csInitializer::CreateEventQueue()` or `csInitializer::CreateEnvironment()`.

Haze Mesh Object

  A haze mesh object is a bit like volumetric light. It represents a 3D volume on which a texture is applied in a fuzzy way.

Light-Map Space

  Two-dimensional (l,m) coordinate-system corresponding to some point on a light-map. Light-map space is closely related to texture space.

Lumel

  A lumel is a pixel on a lightmap. A lumel corresponds with one light value (red, green, blue) and represents the lighting values of a block of texels on the original texture. Usually this block is 16x16 big.

Material

  A material represents how some object or polygon looks. In the most common case a material is just a texture. But a material can contain additional information like detail textures (textures that are blended on top of the base texture). In future materials will be able to do much more.

Mesh Factory

  A mesh factory is an object from which you can create mesh objects. See section Mesh Object Plug-In System.

Mesh Object

  A mesh object represents geometry in Crystal Space. The Crystal Space engine is very modular. The engine itself does not know how to render. It only knows about mesh objects. Every mesh object is responsible for rendering what it represents (using the 3D renderer). Crystal Space supports several mesh objects: things, 3D sprites, 2D sprites, particle systems, haze, terrain engine, ...

Object Registry

  The object registry (represented by the `iObjectRegistry` interface is the central repository for all objects in Crystal Space. Everything in Crystal Space will use the object registry to get the pointer to the objects it is interested in. See also:

  `csInitializer::CreateObjectRegistry()`
  `csInitializer::CreateEnvironment()`

Object Space

  Every object or room is defined with its own local 3D coordinate system typically centered around (0,0,0).

Particle System

  A particle system is another kind of mesh object. Crystal Space supports several particle systems (snow, rain, fire, explosion, emit, ...).

Plugin

  A plugin is a number of classes that can be loaded dynamically into a running Crystal Space application. A plugin is represented by a dynamic library in a format suitable for the host operating system. On Unix like systems this is a ``.so'` file and on Windows systems this is a ``.dll'` file.

Plugin Manager

  The plugin manager is responsible for loading and unloading plugins. A plugin is a shared library of functions that can be loaded dynamically into a running Crystal Space application. On Unix a plugin has the ``.so'` extension and on Windows the ``.dll'` extension is used. Almost everything in the Crystal Space framework is itself a plugin. So the plugin manager is an important object. See also `csInitializer::CreatePluginManager()` or `csInitializer::CreateEnvironment()`.

Portal

  A Portal is one of the polygons of a thing mesh object which will not be texture mapped (unless it has a semi-transparent texture). Instead another sector (visible through that portal) will be drawn. A portal may even point back into the sector in which it is contained. This is useful for portals which act as mirrors. A more general form of a mirror is a space warping portal. This way a portal can go to any place in the world.

Procedural Texture

  A procedural texture is a special texture that has a 3D renderer associated with it. This means that you can change the image on the procedural texture by drawing on it. Since the procedural texture has a full 3D renderer associated with it you can even use the 3D engine to render on a texture. Procedural textures can be used on all objects in Crystal Space that can use textures.

Region

  A region in Crystal Space is a collection of objects (textures, materials, mesh objects, mesh factories, sectors, sequences, triggers, shared variables, collections, ...). Regions are not a geometrical concept. It is possible to define a region which contains all wall geometry and a region which contains all moving geometry. Usually though, regions represent some area in the world. You can use regions to dynamically load/unload parts of the world. This is useful if you have really big worlds that don't fit in memory at once.

Reporter

  The reporter is a plugin in Crystal Space that listens to messages. It supports the notion of errors, warnings, and notification messages. All components in Crystal Space use the reporter to report about unusual situations. An application can be aware of the reporter in two ways: it can either query the messages at regular intervals or else it can install a reporter listener. There is also a standard reporter listener plugin in Crystal Space which will use the console to output notification messages and use other means to report errors.

Reporter Listener

  A reporter listener in general is an entity that can register itself with a reporter to listen to message that arrive on that reporter. There is also a standard reporter listener plugin that you can use so you don't need to write your own reporter listener.

SCF

  The shared class facility. A mechanism for managing plugin modules and treating objects in a uniform manner. Also manages reference counting. See section Shared Class Facility (SCF).

Screen Space

  Two-dimensional coordinate-system corresponding to physical screen coordinates. Screen space is perspective corrected camera space.

Sector

  A sector is simply a container of geometry. It contains several mesh objects which will represent the geometry of the sector. A common mesh object is the thing mesh object which is usually used to put walls around a sector (that way the sector represents a room). Other mesh objects like 3d sprites can be used for actors.

Texel

  A texel is a pixel on a texture. For example, an 128x128 texture has 128x128 texels. On screen this may result in more or fewer pixels depending on how far away the object is on which the texture is used and also on how the texture is scaled on the object.

Texture Space

  Two-dimensional (u,v) coordinate-system corresponding to some point on a texture. Texture space is given by a transformation matrix and vector going from object space to texture space.

Thing Mesh Object

  A mesh object which is often used to represent walls of a sector but can in general be used to represent many more kinds of objects.

Virtual Clock

  Most Crystal Space applications will be time-based. The virtual clock supports the notion of CURRENT TIME and ELAPSED TIME. It is called a virtual clock because it doesn't necessarily have to correspond with real time. A game can be paused for example. Note that a well-behaved game should always take elapsed time (between two frames) into consideration for calculating what could have happened in that time. This is important especially for physics calculations and also for speed of moving objects. You want an object moving at some speed to move with the same speed on a system with low framerates compared to a system with high framerates. See also `csInitializer::CreateVirtualClock()` or `csInitializer::CreateEnvironment()`.

World Space

  Three-dimensional coordinate-system corresponding to the world in which all objects live. Mesh objects are mapped from object space to world space via a matrix transformation.

VFS

  The virtual file system. A mechanism for unifying filesystem access between various platforms. Using this a Crystal Space application can read and write transparently from ZIP archives. See section Virtual File System (VFS).

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