| ★ APPLICATIONS ★ AIDE A LA CREATION DE JEUX ★ SPRITES ALIVE ★ |
| SPRITES ALIVE (CPC Infos) | SPRITES ALIVE (Amstrad Computer User) |
A box of delights Fancy generating your own sprites without messing around with machine code? We review a package that could let your imagination run wild.
UnHaving looked through the various demonstrations and glanced through the manual, I must 'say that I am impressed. Sprites Alive allows 64 on-screen sprites, animation and sequencing from stored images, pixel smooth motion, collision detection. It also adds 70 RSX commands to Basic, a sprite designer program and a comprehensive manual. All of this for just £19.95 - it has to be a bargain. The system is based around a set of RSX commands which, when loaded into memory, provide control over sprites, sounds, graphics and keyboard/joystick access. The package provides very sophisticated control over the sprites and quite complex programs can be created in a relatively small number of program statements. The biggest problem with the package lies in its sophistication as it is quite hard to figure out how to get started before reading the manual - I know that I should have done this first but I prefer to play around a little to begin with, just to see how easy the package is to use. Fortunately there are six demonstration programs supplied on the disc providing pre-written routines and pre-drawn sprites that can be messed about with to get used to the large number of commands. The basic operation of the system uses up to sixty-four drawings, any or each of which can be assigned to a sprite. This means that a number of sprites can use the same definition or drawing, giving a great saving in memory. The drawings themselves can be created on screen (modes 0 and 1 only) and then copied into memory as a sprite definition, or drawn with the supplied sprite designer and loaded from disc. There is an oddity here in that although there is a command to load the sprite designer drawings automatically into memory there is none to save them to disc. Attaching the sprites to drawings is quite simple, as is assigning direction and speed. Once these basic parameters have been set up, all the sprites can be set in motion either individually or with the overall command MOVE ALL. This means that a Basic loop with a |MOVEALL command in it is all that is needed to get everything moving. There can be up to sixty-four sprites on the screen at any one time -though things get a little slow with this many - and of these there are two main types: joystick or keyboard-controlled and standard sprites. The first are controlled directly by the movement of the joystick or by keypresses on the keyboard. You can select which directions and which keys to use, and also the speed at which the sprite moves. Thus, there is an easy way of providing the user with a playing sprite (e.g. a bat or a spaceship) without any special routines for reading the joystick or keyboard. This is a theme that runs through the whole package; commands are designed to take the work out of programming.
Collisions are automatic and of three types: stop, disappear and bounce. Depending on how it was set up, the sprite stops, disappears, or bounces when it hits another sprite. No program intervention is required, though more basic functions are supplied to let the user know which sprites collided. Again, the package is comprehensive in that although there are many complex commands, the basics are still available: the joystick and keyboard can be read, for example, as well as being used for auto-control of sprites. There are sixty-two standard sprites, each of which measures up to 32x32 pixels. Each can be given a direction and speed, a collision attribute, a box to limit its movement, and an attribute defining what it does when it hits the edge of the screen. There are also a number of 'feedback' commands that allow information about the sprites to be fed back to the user program. The position, direction and collision status can be read for each sprite as well as miscellaneous system attributes such as the amount of free memory. As well as simple moving sprites, there are a set of commands that allow animation sequences to be created. The drawings to be used in the definition are linked to the sprite and then cycled through when the sprite is moved. In addition, the sequence of drawings used is dependent on the direction of the sprite. This makes animating objects such as walking people, flying dragons and spinning spaceships, very easy. Yet another built-in facility is a set of commands to automate the firing of missiles. Once the various parameters have been defined, a missile can be fired simply by issuing a |SHOOT command for the sprite wishing to fire. Missiles automatically disappear when they reach the side of the screen and stop, giving a collision report, when they hit another sprite. The provision of specialised commands for missiles takes yet another chore away from game writing; this seems to be the main aim of the package. Not satisfied with providing a comprehensive sprite management system, the author has also included a useful set of commands for other functions. Drawings can be placed on the screen in non-sprite form to provide scenery; sprites can be exploded; there is a frame synchronisation command; checks can be made to see whether sprites are stuck together; and screen pixels can be tested and set. Sound effects can be set up and attached to sprites so that when missiles are fired, sprites exploded, or bounces occur, the sound will be initiated. The provision of nodes is a rather unusual facility. These allow mazes to be created that constrain the sprite positions within them. A sprite can be moving in a certain direction and hit upon a node. The definition of the node will then tell the sprite supervisor what direction the sprite can take. The example given is a Pacman-type game where the nodes are the junctions: the ghosts wander around the maze changing direction when they hit a junction - defined as nodes. As nodes are fairly difficult to set up, there is a node designer program supplied on disc that helps out. Once defined, the node set can be loaded into the game. Sprites moving around the maze can be set to pursue the joystick or keyboard sprite or flee from it; it seems to be tailor-made for creating a Pacman-type game. Sprites Alive is aimed at the user who can program in Basic but who does not want to get dirty hands messing about with all that horrible machine code. It removes all the hard work and makes using sprites very, very easy. ACU #9001 |
|  |
