3D CONSTRUCTION KIT

4. INTRODUCTION TO FREESCAPE

The 3D CONSTRUCTION KIT uses an enhanced version of the FREESCAPE system. The system allows you to represent a virtual world that you can move around and interact with. This world is represented in three dimensions, known as X, Y and Z.

• X is equivalent to left and right.
• Y is equivalent to up and down.
• Z is equivalent to near and far.

Movement around the world is achieved by using the icons in the editor (refer to later sections), or by using the keys listed in the appendix. Pressing the CONTROL key on Amstrad or Commodore, or SYMBOL SHIFT on Spectrum, whilst moving or turning speeds up the action.

AREAS

The world is divided into regions known as 'AREAS'. Each area is like a box and has a set size of 8192 (X) 4096 (Y) 8192 (Z) units. These units are an arbitrary form of measurement which could easily be thought of as being millimetres, centimetres or metres. One unit is the smallest distance that you can move through.

X, Y & Z

A co-ordinate of X=0 Y=0 Z=0 (View: 0000,0000,0000) represents the nearest bottom, left hand corner of an area.
The world is seen from a single viewpoint which occupies one unit, looking in different directions. The direction is represented by three angles:

• X rotation represents looking up or down (pitch)
• Y rotation represents looking left or right (yaw)
• Z rotation represents looking sideways (tilting your head) (roll)

These rotations are measured in degrees and 360 degrees means that you have turned full circle. Rotations are limited to multiples of 5 degree steps. Rotations of X=O Y=O Z=O (ROT: 000,000,000) means that you are looking straight ahead. Changing the Y rotation by 180 (ROT: 000,180,000) by doing a U-turn, means that you are looking directly behind you. Changing the X rotation to 90 (ROT: 090,000,000) means that you are looking straight down. An X rotation of 270 (ROT: 270,000,000) means that you are looking straight up.

There can be up to 254 different AREAS defined by the user. An AREA can be used to represent a room of a house or an "outdoor" region. You can not travel beyond the boundary of an area.

AREAS have no geographical relation to each other, but are tied together by ENTRANCES. An ENTRANCE has a position and view direction. The user can then be placed at an ENTRANCE position in a specific AREA by some form of trigger (ie. walking into a door. This could effectively "move" the viewer from a hall (one AREA) into a room (another AREA).

OBJECTS

Objects can be placed into an area to make the environment. These are solid and, as such, cannot be passed through when moving. Objects can have different sizes in X, Y and Z directions. Object position and size are measured in a different co-ordinate system to the 3D world. One unit in Object co-ordinates is equal to 64 units in the 3D world system. ie. an Object with a size of 1 unit takes up 64 units in the 3D world. Objects must be placed at 64 world unit boundaries, i.e. it is not possible to place an object at co-ordinate 32 in world units.

There are several basic object types ("PRIMITIVES") which can be re-sized and combined to make larger, more complicated objects such as buildings, trees etc.
The primitive objects consist of:

• Cuboids
  3 Dimensional boxes where the sides can be stretched and shrunk in 3 directions (X, Y and Z).


• Pyramids
  FREESCAPE pyramids are similar to conventional pyramids but are truncated at the top. (They are initially flat on the top). A FREESCAPE pyramid, like the cube, can be stretched and shrunk in 3 directions, but can have its sides pushed in to form a true pyramid or pushed out to form a cuboid. The pyramid can be rotated so that its base is on any of its six sides.


• Rectangles
  Flat (2 dimensional) boxes whose sides can be stretched and shrunk in three directions at any time.


• Lines
  Two points in 3D space joined together form a line. These two points may be moved in three directions.


• Triangles
  Three points in 3D space form a triangle. These points may be moved in three directions.


• Quadrilaterals
  Four points in 3D space form a quadrilateral. This can be non-rectangular. These points may be moved in three directions.


• Pentagons
  As triangles but with five points


• Hexagons
  As triangles but with six points.


• Sensors
  Single 3D points which can be moved in three directions. Sensors have the ability to detect your presence within a defined distance and even to fire at you! These are described in greater detail later on.

Objects such as pyramids and triangles, which do not occupy a whole cube of space, act like solid cubes when moving around the 3D world. For example, it is not possible to stand on the slope of a pyramid. This cube is known as the object's BOUNDING CUBE.

When editing points within these objects, the points are stored as a fraction of the total object size. This fraction is represented as a number between 0 and 63, where 0 means that the point is at one side (minimum) of the cube and 63 means it is at the opposite side (maximum). Each point has a different scale in each of the three directions (X,Y and Z) to show its position with the object's BOUNDING CUBE.

For example: to make a pyramid with the apex (the pointed top) in the middle of the face of the BOUNDING CUBE, the apex would have X and Z values of 32 and a Y value of 63.

OBJECT ATTRIBUTES

Objects can exist in three states: VISIBLE, INVISIBLE or DESTROYED:

• VISIBLE:
  The object is present in the world as a solid form.


• INVISIBLE:
  The object is not present in the world but can be brought into the world by being made visible.


• DESTROYED:
  Once an object is destroyed it is invisible and cannot be made visible again (until the world is reset).

OBJECT COLOURS (SHADES)

Each side of an object can have a different shade. A shade is made up of a mixture of the colours available on the computer used.

The first shade (number 0) has a special property in that it is not drawn. This can be used to improve the speed of drawing the 3D world when used on object sides which are never seen, such as the under side of a house or the back of a door which is placed against a wall.

By painting all of the sides of an object with shade 0 it is possible to have an object which cannot be seen but which is solid and cannot be moved through. Note: In this case the object's attribute will be set to VISIBLE even though it cannot be seen. This can be used to produce invisible barriers or invisible triggers on floors.

GLOBALS

In order to conserve memory, common objects may be stored in a reserved area known as the GLOBALS AREA (AREA 255). These objects can be placed in any area by using the GLOBAL option in the editor. For example, a floor that would be duplicated in other areas could be defined once as an object in the GLOBALS AREA and displayed in each area that would have the same floor. However, an object that is used globally will only appear at the same co-ordinate position as it was defined in. So a tree defined in the corner of the GLOBALS AREA can only appear in the same corner of the AREAS it appears in.

INTERACTION WITH OBJECTS

Events or reactions can be caused by interacting with objects within the environment. Objects may be triggered to respond to being shot, activated (touched/pressed/manipulated), collided with or walked on.

In order to shoot or activate an object, a 'sight' mode is selected (by pressing the SPACE BAR) whereupon a cross-hair appears and is controlled using the normal movement keys or joystick. After targetting an object, the fire button or 0 key, when pressed, will then shoot at that object. To activate a targetted object the "A" key is pressed. However, an object will only be "activated" if the object is within a predefined distance known as the ACTIVE RANGE.

SENSORS

A SENSOR is a special type of object that will detect your presence if you are within a set distance from it. This allows reactions to occur when approaching an object. A Sensor can also be set to respond by firing back at you at a given rate.

CONDITIONS - THE FREESCAPE COMMAND LANGUAGE (FCL)

In order to interact with objects, checks and actions have to be defined in the form of short programs called CONDITIONS.

CONDITIONS are written using instructions which make up the FREESCAPE COMMAND LANGUAGE (FCL). FCL has a very simple but powerful set of commands which allow you to manipulate and respond to any occurances.

There is also a bank of memory which can be used by the user to store and view information relating to the environment and events. Each memory cell is called a VARIABLE. A VARIABLE can store a value between 0 and 255. There are 128 of these memory cells and are numbered 0 - 127. The first 112 (0-111) are free for the user to use for storage, whilst the last 16 (112-127) are defined and used by the system but can be viewed by the user and acted upon, if desired.

There are various categories of instructions in FCL and they are as follows:

• VARIABLE MANIPULATION
  This set of instructions act upon values stored in the VARIABLE memory cells. These include commands to add to and subtract values from VARIABLES, comparisons of values and setting a value.


• OBJECT MANIPULATION
  This set of instructions can alter the attributes of a specified object. There are instructions to visiblise, invisiblise, destroy and swap the visibility of objects.


• VEHICLE COMMANDS
  This set of instructions affect the type of movement you have within the environment. They allow you to set movement to crawling, walking, running and flying. A command is also available to move the user to a specified ENTRANCE in a specified AREA.


• CONDITIONAL INSTRUCTIONS
  This set of instructions allow the execution of segments of programs depending on the outcome of specific checks, such as: If a particular object is shot, if a particular object is collided with, if a SENSOR has sensed you etc.


• MISCELLANEOUS COMMANDS
  This set of instructions deal with functions such as printing text messages, setting colours, playing sounds and setting the TIMER. The TIMER is a device that can be set to trigger a set of conditions at a defined regular interval of time.

CONDITION ROUTINES

Condition Routines (the short programs written in FCL), are stored as lists. Each list is given a number for identification. There are three types of groups of conditional lists. They are:

• GENERAL CONDITIONS


• LOCAL CONDITIONS


• PROCEDURES

General Conditions

These are a set of conditional lists (programs) which are executed all the time. Conditions used in this form are useful for checking for "End Game" situations, maintaining counters, and general overseeing of the whole environment. The first CONDITION in this set is only executed when the environment is reset. This allows you to initialise any variables or events at the start.

Local Conditions

These are a set of conditional lists which are also executed all the time. However, there is a set of local conditions for each AREA. Only the set of conditions associated with the current area will be executed. LOCAL CONDITIONS are useful for checking and acting upon collisions with objects in the current AREA, Sensor handling, or any other occurances that are AREA specific.

Procedures

These are a special set of conditional lists that are only executed at the request of another condition. Their main use is to replace frequently used functions by conditions, only being written once, thus preserving memory. They can also be used to extend the length of a condition list if a condition exceeds the maximum number of lines allowed.

INSTRUMENTS

An Instrument is a device which displays information to the user. Instruments are not visible whilst in the editor, but are visible on the TEST screen or in a Stand-Alone environment. There are two types of Instrument: BARS and NUMERICAL.

• BAR
  Instruments are used to display the value held in a variable as a bar of a length in pixels (dots) equal to that value. They are always one character wide and can either be horizontal or vertical.


• NUMERICAL
  Instruments are used to display the value held in a variable as a decimal figure. They can be set to display to a length of 1 to 5 characters. To display four or five characters, two variables are used to hold the value (see section on "HOW TO USE VARIABLES" and "MORE ABOUT VARIABLES" in the manual).
  

MESSAGES

Messages are a way of communicating to the user by way of printing text to the screen. They are only visible on the TEST screen or in a "Stand-Alone" environment - messages are stored in a list; each item in that list being a single line of text. Each message can be printed to the screen by referring to its message number and its position at which it should be placed. This allows frequently used messages to be stored once.

LIMITATIONS TO FREESCAPE

As FREESCAPE uses extremely complex mathematical algorithms to represent the 3D world on a 2D screen, there are a few basic limitations to what you can do:

• Objects should not overlap. The bounding cube of one object should not occupy the same 3D space as any other. This is especially true when you have GLOBAL OBJECTS or objects which are made visible which overlap with normal objects.


• The number of visible objects in any one AREA is limited due to memory restrictions. Excess objects are not drawn. The maximum number of objects depends on the computer you are using.

THE 3D KIT PROGRAMS

On 48K/64K machines such as the Spectrum 48K, CPC464, CPC664, CPC464+ or Commodore 64, the Kit is split up into three programs:

• The ENVIRONMENT Editor
  This allows you to edit Objects, Areas, Entrances and Colours.


• The CONDITION Editor
  This allows you to edit the Conditions, Instruments, Messages and to test the world without the Editor screen.


• The FREESCAPE COMPILER
  This allows you to combine your 3D world together with your own border to create a Stand-Alone program which can run without the Kit.

DATA can be loaded and saved to and from each program to create the complete world.

On 128K machines such as Spectrum 128K, +2, +2A, +3, CPC6128 or CPC6128+ (excluding Commodore 128), the Environment Editor and the Condition Editor are combined and more memory is available to create larger worlds.