GAC : Der Graphic Adventure Creator (CPC Amstrad International)GAC : The Graphic Adventure CreatorGenesis vs. Graphic Adventure CreatorGAC
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Two adventure writing programs do battle on the shop shelves, Tony Kendle adjudicates

Until recently 'adventure creators'and 'The Quill'have been synonymous terms, which is really as shortsighted as calling all computer games PONG. Although Gilsoft implemented the original idea it was inevitable that improvements would appear and there have just been two new second generation adventure creators released for the CPC computers, Genesis from CRL and Incentive Software's more prosaicly named Graphic Adventure Creator.
Even a relative novice can program a simple adventure, the trick is making them fast, and squeezing the most out of the memory. Adventure creators do this for you, and let you concentrate your imagination on making the plot worth playing.

Theoretically they attract people who are talented 'script-writers'but have little programming experience. Unfortunately the Quill demonstrated that equal scope exists for abysmal storylines to be churned out at a frightful rate. However sufficient professional quality exceptions showed that as the utilities improve in power and versatility it will become masochistic not to use one, like writing your own word processor before typing a letter. All leading adventure writers, from Level 9 to Scott Adams, already have skeleton systems of their own into which they insert the plot for each game. The ideal home utility would be no more than a friendly version of such. It should be powerful, simple and efficient in its data storage. How well do GAC and Genesis shape up?


As standards advance Quilled adventures have begun to look rather tired. Certain features are becoming increasingly important in selling programs, most notably graphics and sophisticated language parsing, it is important for the adventure creators to keep up with these developments. Graphics in particular are the mainstay of almost all hit releases. Both new programs include a graphics designer in the price, a considerable improvement on the expensive Quill and Illustrator combination. Genesis comes in three parts, one for graphics, one for text and one to join the resulting files into a finished adventure. This means you can't test both halves together. More importantly the process involves four tape changes, there is no disc option and the adventure is saved with a special loader meaning that you can't transfer it or make backups without going through the whole palaver again. GAC is nicer in that it offers a disc option, is entirely self contained and yet there does not seem to be a restriction in the room available for data since ultimately a 40K length game can be produced.

Unlike Screen Designer both store graphics as a series of routines used to redraw them at appropriate points in the game, not as binary data. Thus a simple picture can fit into a fraction of 1K as opposed to 16K. You have to wait longer for the picture to re-appear, and there is a trade off between the memory used and the detail you put into the drawing but even so Incentive say a good picture is possible in 200 bytes, and a masterpiece in 0.5K.
GAC uses the top half of the screen for pictures. They are constructed from a small series of options, you can draw lines, ellipses, rectangles, dots, fast fill and of course delete the last command. Once defined everything redraws quickly. You are restricted to mode 1 giving four colours but a stippling option combines these to produce ten shades.

Ellipse and Rectangle work on a rubber banding principle, they can be stretched horizontally or vertically to make a range of shapes. These options also produce either vertical or horizontal lines if they are only 1 pixel wide. More complex shapes are constructed from plotted points and lines but these use up memory at a faster rate.

As you draw something the necessary graphics commands to recreate it are stored automatically. You are given editing facilities that let you step backwards or forwards through the picture making insertions or corrections. It's easy to use but any blunders or dithering around you do on screen is recreated every time. Erasing wrong moves is therefore important to make the drawing as efficient as possible. However there can be more positive effects to the system used. Incentive suggest that a simple form of animation, such as moving shadows, can be produced by using repetetive colour fills.

Defined pictures can be merged into later ones with almost no extra cost in memory so a library of basic shapes can be designed and combined to produce each new screen, a technique used in many commercial releases. The result is a composite image showing all of the lines and some of the fills may therefore work in unexpected ways. A more powerful system would be to 'overprint' the existing picture, obscuring anything beneath, but difficult to implement.

Genesis also has rubber banding graphics routines, box, line, curve, fill etc. Editing facilities are not as good as in GAC and it is slower but there are some extra virtuoso touches. There is no stippling facility but you can include User Defined Graphic characters. Up to twenty possible graphic windows can be defined, and two possible text windows. Again two pictures can be superimposed on screen and defined windows can overlap so that small pictures can be combined into larger ones. It also allows you to change the picture display AFTER a command has been typed so the graphics reflect the text action. Even more impressive is that screen modes can be mixed, allowing 16 colour low res graphics to be mixed with 80 column text for example but the effect tends to flicker during sound output or picture drawing.

If you still don't like the results GAC lets you toggle between text only or text and pictures during play. Genesis has a control key combination for skipping the picture being drawn.

Sound is an underexploited area of adventures and it would be no surprise if it was left out of both programs. Look for the Arnold adventure series from Nemesis to see how effective sound effects can be. Top marks therefore to CRL for including it in Genesis. Envelope shaping is provided as well as a routine that programs certain keys to produce musical notes. An entire three channel soundtrack can be created.

Language parsing, the ability of the game to understand the player's commands, is typically restricted to a primitive Verb-Noun structure in adventures e.g. "Take Sword". GAC excells here, it understands large sentences, adverbs, conjunctions and even the generic noun 'it'. An example would be "Take the sword and go north and quickly stick it in the dragon". Not bad. I hope people make proper use of this when writing and playing the games, although I find it hard to break the verb-noun habit.

Genesis is more basic in its parsing abilities but it is better than the Quill in that up to two command nouns can be handled at once. "Hit wall with head" is the colourful example they use.

Short demo adventures come with each program. 'In Like Minsk' from CRL is surprisingly poor graphically but full of inventive and funny text, whilst 'Ransom' from Incentive has no plot to speak off but excellent graphics which probably goes to prove something.


Despite all the menus and extra features that you may not want to use, a well written machine code utility may allow more room for data than a normal Basic program.

GAC gives you just over 25000 bytes to write the game but this can be divided how you want between pictures and text. Automatic text compression means that a 200 location adventure is possible. In fact Incentive are currently converting their hit Spectrum adventure 'Mountains Of Kef using GAC and the compression has reduced the game to a fraction of its original size, leaving ample room for graphics.

When saved as a program that runs independant of the GAC itself, the data file expands to a maximum size of about 41K since some of the main program routines are saved with it.

Genesis leaves 25700 bytes free for text and the program logic and about 10000 bytes for pictures and sound. Of course the latter cannot be utilised in a text only adventure. Text compression is possible by defining 'subroutine messages'that are inserted into longer text. You are however limited to 250 messages in total which includes descriptions, clues and so on. This may prove restrictive in some game designs even without using them up on sub-messages.

Neither program uses the extra memory of the 6128 but I suppose that this does at least guarantee a wider audience for the resulting game.

Ease of use 

Both utilities use a kind of programming language with specialised syntax and reserved keywords to control what happens when you type in a command. They rely on the fact that all adventures work in similar ways. At the heart are logic routines which handle the operation of the game and the data for permissable verbs, room and object descriptions. This logic runs along the lines of "if location = 1 then print room description 1, if input command is 'north' then let location = 2" and so on. The content of the message and description text is completely irrelevent and isn't even considered by the computer, or the author sometimes.

Both utilities provide counters and status markers to control things such as the amount carriable or the length of time a lamp remains alight.
For sheer ease of use nothing to date can lay a finger to GAC. Everything is made simple by menus and prompts it is all easily editable. Once you have defined your adventure on paper all you do is enter the recognised nouns, verbs, messages, descriptions etc. and the connections between the rooms. All of these are numbered and synonyms are handled by giving them the same number.

Everything then hinges on what are called high and low priority conditions entered in a Basic-like language. The difference is that the former take effect as soon as you enter a room, the latter only after you have entered a command. An example is given later.

If GAC is like Basic then Genesis is like 'C' or one of the other less friendly languages. It looks like something a commercial programmer would have written for their own use. It can perhaps be made to hum, but for most people is simply baffling. Again you begin by entering the verbs, nouns, messages and so on and again there is a purpose built logic handling language but Genesis seems to be far less neatly conceived than GAC, albeit more flexible, and is provided with an almost deliberately obscure choice of syntax and keywords. Similarly the manual supplied with GAC is chatty and easy to follow, the Genesis prose soon has people sighing, rubbing their heads and mumbling about 'object sequences'and 'action operators'.
Consider these two examples taken from the manuals, both designed to print the description of the current location.



The former creates a loop that tests every object in turn looking at the flags for where it can be found. The latter has a nice straightforward keyword that anticipates one of the most common actions you will want to program into your adventure.
It may be an extreme example but the essential difference holds true to a large extent, and to Genesis's great disadvantage. The point is that GAC is so easy to grasp and so fluent to use that within minutes of loading you feel the urge to sit and write something.

The choice between the two ultimately depends on what you need. Each has strengths and weaknesses and both are able to produce highly professional end results. Genesis is cheaper and provides more powerful graphics with sound, but only GAC really meets the objective of being 'a programming aid for non- programmers'.

Tony Kendle, ACU #8602

★ YEAR: 1985


» Der  Graphic  Adventure  Creator    GERMANDATE: 2013-09-03
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Manuels d'utilisation & docs:
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» Graphic  Adventure  Creator    ENGLISH    MANUALDATE: 2014-05-05
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L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent  du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko.