REVIEWS COURTESY OF ZXSR

RD Digital Tracer
RD Laboratories
1983
Crash Issue 6, Jul 1984   page(s) 102

MAKING AN IMPRESSION

Faced with the problem of copying an existing drawing, pattern or map on to the Spectrum TV screen, there would be little hope of a fast and simple job. Drawing grids, listing coordinates, rescaling and inputting either via suitable software or via light pen could simply take hours. Unless of course an RD DIGITAL TRACER were at hand.

CONSTRUCTION

The tracer consists of a double jointed arm with a hair cross sight at its end. The knee joints contain potentiometers which detect in combination with the supplied software the exact location of the hair cross in reference to the tracers base. The tracer interface unit does not inspire confidence, in fact the enclosure is constructed out of a standard cassette box and certainly doesn't reflect the high cost of the unit. Nevertheless the tracer performed immaculately throughout the test and proved reliable.

INSTLLATION

The tracer can reach a maximum tracing area of 300 x 300mm using automatic scaling, but the nominal area is 256 x 176mm for normal draw mode. The base is fitted in position with a damp or with the double-sided adhesive strip supplied. A template is provided for positioning the tracing sheet grid in the correct location. The interface of the tracer is plugged into the back of the Spectrum (with the power supply disconnected!) or into the extension port of the printer edge connection. The software cassette DT2 is loaded and the system is ready.

SOFTWARE

The cassette contains five programs:

DRAW: All general purpose draw features including outline paint and copy.

SCALE: The drawing is transferred to screen scaled up or down, reversed left to right and upside down and repositioned.

RETRACE: Stores a string of drawing commands and coordinates for later retracing. In practical terms this means that it stores an outline drawing which can be recalled repetitively.

GRAPHICS: Sets up an array of user defined graphics

COMP: Comp 48 includes all four above progams. Comp 16 includes DRAW, SCALE and RETRACE. RETRACE, SCALE and GRAPHICS must be run from within DRAW and must therefore be merged with DRAW.

The DRAW program prompts entry of background and paper colour and a flashing cross wire cursor displays the current position of the trace head. If the trace head is moved out of the tracing area, a warning BEEP will sound. A large or small or invisible cursor may be selected. Border, paper and ink colour changes, screen clearing, display of colour character grid, line erasing within character square, etc, facilitate the production of the drawing. Drawing can be accomplished either in normal mode by holding down key W (pen down) or in continuous mode (toggle key C). Pressing key E will create thick lines, while key Q plots single points.

Special drawing functions are provided including straight line, quarter, half and full circle, rectangle and right angles. All these facilities permit rapid production of complex outline drawings. For area filling four different functions are available:

key g: paints solids

key F hatches (alternate horizontal lines)

key D hatches (every third line)

(Sym) M: Toggles shading limits (shading to edge)

Text may be printed using key P for normal, key M for inverse and key V for flash after positioning the cursor at the desired print position. The screen display may be copied on the printer or saved on cassette at any time and recalled at a later date from within the DRAW programme for further modification.

SCALE

When operating the tracer with DRAW the drawing on the tracing sheet is transferred with a fixed nominal scale of 1mm to 1 pxel. With the program SCALE the display image may be moved up and down, left and right, scaled up and down, reversed left to right and turned upside down or any combination of these. Automatic scaling can be achieved by:

Figure entry mode: by inputting the coordinates of the desired rectangle on the screen. Upon completion the cursor will move only within the confines of this rectangle when moving the tracing arm across the entire nominal tracing area.

Drawn entry mode: The four coordinates are input automatically by the screen cursor. By indicating the lower left and upper right position with the screen cursor, the required area rectangle will be displayed temporarily or permanently.

Single point entry: inputing a scale factor and positioning the trace head at a reference point on the drawing to be traced. The x and y coordinates may be read and input.

RETRACE

The program RETRACE stores consecutive points from the tracer, the x and y coordinates and the key pressed being stored in a string array. The program allows to trace many outlines, stores at different points in the array and to recall any one in particular commencing the retrace at the appropriate sample number. Up to 5,000 samples may be stored on a 48K Spectrum or 500 With a 16K memory.

GRAPHICS

DRAW enables text to be printed normal inverse and flashing including standard graphic symbols or UDGs. With GRAPHICS a new character set may be generated and saved to tape for later use. The current character set is displayed. Entering the letter to be changed the 8 x 8 dot matrix is displayed and the character may be redesigned with the use of keys 1 and 0. If an error is made while generating a line of the character it is possible to return to the beginning of that line.

The programs SCALE, RETRACE and GRAPHICS must be merged with DRAW to operate. However the composite program may be loaded, which contains all the above mentioned facilities. The programmer may use individual routines from the utility program and merge them with his own.

Furthermore he may add additional subroutines to be called by non-assigned keys and customise the program to suit his requirements. All this can be done in Basic and should not prove too difficult. A complete listing is provided for this purpose.

CONCLUSION

The RD DIGITAL TRACER runs rings round the usual drawing utilities with and without light pens. The tracing arm is definitely more easy and accurate to use than a light pen. However its application lies not in sketching and freehand drawing, but is limited to the copying or tracing of existing drawings. The extra features of SCALE, RETRACE and GRAPHICS increases the efficiency of the system and makes it the most versatile tracing utensil on the market. The only drawback is the price of £55.50 which makes it a rather expensive Spectrum add-on, and limits its application to the serious or well off Spectrum owner.


REVIEW BY: Franco Frey

Transcript by Chris Bourne

Your Computer Issue 1, Jan 1983   page(s) 46,47

How often have you wanted to input a picture or a design straight into your home computer? Simon Beesley evaluates two products for the BBC and Sinclair machines which claim to allow you to do just that.

The RD Digital Tracer enables pictures to be drawn or copied to the Spectrum's screen. It consists of a mechanical arm which is hinged at the base and the middle and can be mounted on a drawing board. At each joint of the arm there is an angular transducer. Signals sent by the transducers are digitised by an interface board, plugged into the rear of the Spectrum. The board has a connection to take a ZX Printer or Microdrive.

The kit also includes a software cassette, an instruction booklet, a tracing sheet and a template for aligning the tracer with the tracing sheet.

DRAWING PROGRAM

Once you have loaded a drawing program you can transfer a picture to the screen by moving the head of the tracing arm.

Probably the most important question to answer is how easy is it to transfer an outline to the screen accurately. The tracer picks up movements within an area 30cm, by 20cm. Since the Spectrum's resolution is 255 pixels by 175 this gives just over a millimetre per pixel. The arm certainly responds to movements this small, but achieving an exact screen copy depends more on how much fine control the arm's action allows.

As with a joystick, the problem is to strike a balance between too much give and too much resistance: few people can manage to control a joystick steadily if it moves too freely, and, on the other hand, too stiff an action is equally likely to result in jerkiness.

The RD Tracer scores quite highly in this department. Although the action is fairly free you can steady its movement by putting pressure on a pencil inserted in the tracing head.

Four programs are included on the software cassette, which can be used alone or merged together. The main drawing program provides a number of plotting options and also allows you to use Spectrum Basic's plotting functions. Single-letter entries allow you to plot individual points or draw a continuous line, change the background or foreground colour, delete lines and print text. Among the other options is a facility for filling in or shading the area enclosing the tracer. The position of the tracer on the screen can be indicated by a small or large crosswire.

You can draw a circle using the Spectrum's Circle command and define the centre and radius through the tracer position. The Spectrum's facility for saving the screen to tape is also available.

THE PLOTTING MODES

These and other plotting modes enable you to copy a picture to the screen as closely as the Spectrum's resolution and colour range permits. But putting a detailed colour picture on the screen could be a lengthy process. The programs are written in Basic and some of the routines are rather slow.

For example, keyboard entries are not detected instantly and filling an enclosed area can make demands on your patience. Bursts of rapid sketching are too much for the tracer to copy faithfully.

This is a software, not a hardware, problem. To be fair, the routines RD Laboratories supplies are adequate but machine-code versions would make the tracer much more effective.

The software cassette also contains a program which prints the x and y co-ordinates of the tracer at the top of the screen as it moves and allows the origin and scale of the plotting co-ordinates to be changed. The third program provides a blind-drawing facility; points can be inputted at greater speed than normal and are then drawn at a slower speed.

Lastly, there is a program to design characters which does not make use of the tracer and which is given free to the buyer.

While the tracer has an obvious use in schools and could perhaps even find a place in an office, RD Laboratories say that they have taken at least 50 percent of their orders from home users.

At a price of £49.95, inclusive of VAT and postage, this is the first such device to be produced which is suitable for low-cost micros.

It will also work with the ZX-81 and two short programs are included for this purpose but the ZX-81's limited screen resolution gives it only a limited application.

SOFTWARE SUPPORT

RD Laboratories intends to support the tracer with more general-purpose and specialised software packages. Details from 5 Kennedy Road, Dane End, Ware, Hertfordshire SG12 0LU. Telephone: 0920-84380.

CONCLUSIONS

Both devices allow a picture to copied to the screen accurately, if rather slowly.

The Spectrum Tracer's price and light-weight construction make it suitable for the hobbyist and for use in schools.

Software for the Tracer is adequate but could be greatly improved upon.

The BBC Graphics Tablet has a more solid design which affords a greater degree of fine control. With appropriate software it could find a wider application, outside the confines of the home and classroom.

The program supplied with the BBC Tablet is barely satisfactory and scarcely justifies its relatively high cost.


REVIEW BY: Simon Beesley

Transcript by Chris Bourne

ZX Computing Issue 6, Apr 1983   page(s) 31

ADDING ON YOUR SPECTRUM

Our review team take a brief look at some of the hardware add-ons fir the ZX Spectrum.

Now that the ZX Spectrum has well and truly established itself on the micro market, it is amply supported by a wealth of hardware add-ons. Most of these peripheral devices have been manufactured by the people who supported the ZX81, but just as the Spectrum has attracted new users with its prowess, so too has it attracted a new following from the add-on manufacturers.

In this brief guide, we have not tried to cover all the devices currently available on the market but rather give you a flavour of the technology you can add on to your Spectrum. As joysticks are an obvious favourite, these have been covered in some detail whereas RAM packs are fairly standard and so have only been briefly touched on. Also included in this section area number of quite specialised add-ons like sound units and a digital tracer.

If you own a Spectrum, you will no doubt have begun to realise the potential you hold in your hands. Over the next few pages you will hopefully see further applications for you and your computer to explore.

The device from RD Laboratories must be singled out as special if only for its cheap price - this sort of technology has normally only been available for up-market computers.

The Digital Tracer comes complete with an instruction booklet, a tracing sheet and a template which is used for alignment. The cassette supplied with the package includes four programs which can be used individually or MERGEd and used together. Using the programs you can plot individual points, draw lines, alter the background and foreground colours, shading areas enclosed by the tracer, printing and editing of text on screen. Thus, you could, using the Digital Tracer, transfer a picture or diagram to the screen, further develop it using the editing facilities, and then SAVE the screen to tape.

In practice, however, the digital tracer is a little tricky to use. As you draw using the tracer, a crosshair target comes up on the screen, and by skillful manipulation, very accurate drawing can be accomplished. However, when you start trying to fill in areas of the screen, or adding fine detail to your drawing, it does get a bit awkward. Since the software is written in BASIC, rather than machine code, it would seem fair to lay the blame for any of the tracer's shortcomings at the software's door.

Other programs on the cassette include a co-ordinates program which can be used to move an origin and x and y coordinates around the screen. Another program allows you to draw at a fast speed with the tracer, with the computer plotting the points at a slower rate. And the last program is used to define user characters, but is not intended for use with the tracer.

All in all, a useful device which faithfully reproduces the drawing action on screen. The Digital Tracer is available at £49.95. For more details on this product contact RD Laboratories, Unit 20, Court Road Industrial Estate, Cum Barn, Gwent NP44 3AS.


Transcript by Chris Bourne

ZX Computing Issue 22, Dec 1985   page(s) 41

GRAPHICS '85

A comprehensive review of the state of the art by Colin Christmas.

As we see this old year out and welcome the new one in, it's a better time than most to stand back and take stock. Looking back land leaving the prophecies and predictions to others! It must surely be agreed that for Spectrum users with an eye on Graphics it has been a most exciting year. I can't speak for other departments but for me, it has been Christmas every issue.

In this issue I want to do something special take a look at the goodies that have come our way. Our way? Who are We? We are the Graphics Grabbers, Artwork Addicts, Design Doodlers. For us the screen is a window on a world of colour, images, line, shape, pattern, design, texture, light and shade. And like a window it opens out into an exciting new visual world. For business, for profit, for learning for discovering or for pleasure. From the weekend dabbler or doodler to the serious professional, from the games enthusiast to the educational user, from beginner to experienced programmer and right across the age range, you will find Spectrum owners who are hooked on graphics.

It's fairly formidable task - covering the range of Graphics Hardware and Software now available lo Spectrum owners but let's get started.

LIGHTPENS

I've had most success to date, with the package from Dk'tronics. The pen itself is rather like a biro or felt tip pen. It is attached by a wire to a control interface which of course comes with the package. The interface is plugged into the back of the Spectrum. A program on cassette is included.

The glass screen of your monitor is the working area and drawing surface, so some consideration has to be given as to whether this is the way you want to work. Then there are practical aspects such as the distance of your screen from your keyboard, and the fact that you have to work on a perpendicular 'face'. The height of the screen is therefore important if you do not want to suffer from muscle fatigue in your drawing arm.

Lightpens give you a physical contact and interaction with your drawing surface if that is important. Calibrating the pen each time may prove a chore, but after that it's plainsailing - within the limitations of the power of the program. Again it's a good way of getting started or the very basics of graphics, of getting into the picture as it were. Sensibly introduced in the classroom it could be useful aid and introduction for children in an educational context. It is limited though in its potential for advanced or complex screen designs. Graphics Tablets give you similar physical point of con tact with your drawing-surface. This time it is horizontal and again a 'pen' is used. There's a review of the Saga Graphics Pad in this issue. So when you are ready look it up. They certainly take you further than the lightpen. But then you pay a lot more for the facilities they offer.

Now for something almost completely different, the Sinclair LOGO pack. Another excellent starter, but as I have hinted, quite different.

This pack has very obvious educational applications and for very young children. The founding father of the LOGO language intended it as a language for children which would develop logical thinking, introduce young minds to computer programming and have very definite terms of reference for the teaching and development of mathematical concepts. Drawing is achieved by moving a small graphics 'turtle' - a triangle - around the screen. This is done by sending through the computer commands known as Primitive Procedures (mostly single words and abbreviations of those words). Your sense of direction needs to be accurate and formulated mathematically. Once you have established procedures for drawing, say, a square, this group of procedures can be assigned a single word or name which LOGO will then understand as a command to repeat the whole set of procedures.

The emphasis or bias is fundamentally mathematical, arithmetical or geometric. You do not just learn to draw a square, you also learn what makes a square what it is and from there the difference bet ween a square and a rectangle or a parallelogram.

It is a language itself, apart from BASIC. Hence learning to use it is learning to program a computer in another language. The graphic aspect being displayed on the screen is part of the incentive and motivation for progressing with the new language.

Two fairly weighty and comprehensive books or manuals are part of the pack. The first book deals exclusively with Turtle Graphics and is an absorbing and refreshingly different kind of programming experience. The second book acts as a reference manual for Sinclair LOGO, The growth, use and development of LOGO by Spectrum owners, especially in schools will, I think, be affected by the cost factor.

When DREAM SOFTWARE released Computer Aided Designer, my own children had not had their Spectrum for long. They, like me were exploring the full graphics potential of the machine when C.A.D. turned up and kept us enthralled for days. Now, still an old favourite, I would recommend it as another in the 'Starter' category. With very obvious educational values and as a springboard for more ambitious projects later in Design.

The manual is simple and very straightforward - alphabetically leading you through the twenty seven commands available in the program. Some forty custom shaped graphics, UDGs can be designed. By giving precise measurements most geometric shapes can be drawn, filled and so on. It remains impressive after all this time, and the potential for drawing in 3D is considerable.

Similarly, another old favourite, VU-3D from PSION.
This has the added and appeal of enabling the viewer to move around the object in 3D. Graphics and Design, pure and simple. High resolution colour and an incredible understanding of perspectives are real bonuses with this program.

Future designers in the Aircraft or for that matter almost any other industry, may have started young with something like C.A.D. or VU-3D.

I doubt if they would have been able to afford the RD Digital Tracer, from RD Laboratories. This is closer to an instrument than anything else I've come across in graphics and design hardware and software for the Spectrum.

It comes in two versions, the Standard and the Professional. Both are fairly highly technical and sophisticated tools. The Tracer consists of a short fixed arm and pivot from which extends a drawing arm hinged at the centre with another floating pivot which moves across your drawing surface area.

The arm is connected to the computer by a length of cable via an interface plugged into the rear port of the Spectrum. A cardboard template and transparent grid overlay are included for calibration purposes, the tracer is a precision instrument. The software cassette contains five programs. The usual options are offered in the first, plotting single points, construction of basic geometric figures, filling, hatching, change of ink, border, paper colour, adding text, UDGs and so on.

The display image can be moved up, down, and from side to side, scaled up and down, and reversed. Multiple screen images including images at different scales and at different positions can be achieved. By adding other BASIC routines and software, the Tracer's capabilities can be extended into the field of statistical analysis. This immediately puts the Tracer into a specialist Graphics and Display category. Although the Tracer can be used with the ZX81 and 16K Spectrum, its full potential can only really be developed on the 48K and then only by competent programmers. It's a versatile instrument for the specialist.

It's the season of Good will and all that, so why not give a last mention for all whose speciality is Games Designing. It's been around for a while, but standing the test of time in lots of ways. I'm referring of course to the High level User Friendly Realtime Games Designer from Melbourne House. Or as it is more commonly known, HURG.

Still a powerful program and a very good manual. How did they do it in those all time greats like Pacman, Donkey Kong and Space invaders? H.U.R.G. will tell you how.

It's a pretty good list of graphics goodies and that other seasonal expression comes to mind. 'There's something here for everyone.' You have no excuse for not knowing how and from whom in Spectrum Graphics, just how to enjoy the graphics power behind those buttons.


REVIEW BY: Colin Christmas

Transcript by Chris Bourne

All information in this page is provided by ZXSR instead of ZXDB