Amiga Computing - Commodore Is Awesome

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GRAPHICS nyone interested in 3D modelling has, at some point, seen a model so well made it makes them stop and admire the creator's handiwork. Whether it be dinosaurs, animated human faces, or cars with smooth, flowing lines, there are plenty of examples around that make you think 'how did they do Mar Often, the answer is that they used a 3D digitiser to 'scan' a physical object and import its vital statistics to a ray tracing package, where the model is tidied up before textures and other effects are added. Indeed, much of the drudge work in modelling can be done by electronic sidekicks if you have the sort of production budgets enjoyed by Industnal Light and Magic. In high-end digitisers used by movie companies, a scanning laser beam builds up a picture of an object's surface in minute detail before passing the data to a Silicon Graphics machine for interpretation. The 3D artist can build a model in plastic or any other substance, or have it built by the traditional model makers who brought us the Star Wars designs, then digitise it to cut out most of the time-consuming job of translating the model to computer graphics. PRICE DROP For a long time now, small companies and enthusiasts have been unable to use this sort of technology, but a growing number of American manufacturers are releasing smaller, less expensive digitisers which are now coming down in price - enough for them to be a realistic option. One such unit is the Immersion Personal Digitiser which, though still not cheap, is a powerful tool for any modeller. Laser scanning would be tar too expensive, so the personal digitiser makes use of a jointed arm (much like a robot arm) with a stylus on the end. This sits on a bread-board-sized base and is connected to the Amiga via a control box and serial cable. Build quality is as good as you'd expect from a device costing this much. The arm itself is made of tough, thick plastic with a solid brass stylus. and the base board is half an inch thick with rubber feet to stop it sliding around. To avoid any plug difficulties on either side of the Atlantic, the control box uses a standard kettle lead connection, and all necessary cabling Eand for 'lour bum Why not just use splines, or the Forms editor in Imagine? I mean, it's not easy to create organic shapes, but it can be done. Why spend money on a digitiser? Apart from obvious benefits in terms of cutting design and modelling time, 3D digitisers make it much easier to create a complete model with one continuous skin. Until Amiga packages utilise the 'smart skin' techniques found in some Silicon Graphics software, even fairly simple objects such as a human head are difficult to produce without bolting two or more objects together, Three rough models created using the dig/tiger. Note tha t the human face uses more 5amplos then the other two, and is therefore much more eccurate 1• (including a custom serial cable) is supplied_ The units Vedisketch software is installed in no time and uses ARexx macros to enable the digitiser to be controlled directly from Lightwave's Modeller. There are several control macros, but the most important - Get Point - simply passes a position request to the digitiser's control unit which replies with a three dimensional co-ordinate. A point is then created on screen to correspond to the arm's position when the macro was invoked. Hardly any delay is involved in the process. so digitising a long series of points is a simple matter of moving the stylus to a new location with one hand and hitting the relevant function key with the other. The manual suggests using F10 for the Get Points macro, but you can set this system up any way you like Several macros are supplied to ensure agreement between the arm and Lightwave's internal 3D world. Set Origin, for example, can be used to select any point within the arm's reach and treat that point as Modellers equivalent of co-ordinate 0,0,0. and the Set Orientation macro ensures that your digitising table is oriented in the same way as the N the Wjoin will usually show, and there's nothing more realism-killing I than a dirty great line where, for example, M the shoulder joins the arm. Putting bones Into an object N like this will produce decent animated effects, but i with one continuous object the effect is far more Using tmagine'a Forms e ditor So cre a te orga nic sha pe s is convincing. one a nswe r, but it ca n be a ve ry time-consuming proce ss V 4 M Amiga Computing MAY 1995 I g 1 e nog • • t • Even relatively sample shapes, like this pipe bowl, cart be digitised lamter than you could model them from scratch Modeller environment. The latter becom very important because you have an °tail which is too big or awkward to digitise in o piece. By creating a simple triangle Modeller and aligning it with another that y create using the digitiser, users can arm that the centre of the digitiser's universe always in the same Lightwave position. With this common frame of reference, is much easier to ensure that two parts al larger object can be glued together agi once they've been digitised. I say much easier, but the process still is what you'd call a walk in the park. Probal the biggest limitation of digitisers such as II one is that they have problems with large oddly-shaped subjects. At full stretch, the tip of Me stylus will rea about 55cm from the base of the arm. t when you have to loop the arm up and ON an object, this reach comes down to atx 3 1 For objects such as a thigh bone (uSeC 3one of the pre-supplied examples), this me cdigitising in two or more sections and rresulting hassles when the hnished modo a glued together in Lightwave. o For smaller objects, the arm is easily et r ble of digitising a complete object. anc \ l e s s
JOAO! , VklW pipe wad nom obj in ngle bat y ou ensur verse e i ence, trts of r again still isn't 'robably as this large of ill reach irm, b ut .nd o abou t used mean and the nodel ly cape - and its IIMpitiohng • too* wnook is easy ter the lhownorsion When having a go ot obiects such as dillolhoor, but tricky for the user_ This ono doosn't this cat head, projections like the with deo levee *nowt] sample sphnes for a cletailect model ears can make life more diffi cult accuracy is impressive. When the stylus is neid to the subject's surface at a reasonable angle, errors are in the order of about half a n -no to reach a difficult spot with the stylus that a;cents can start to fly around a little. l If the angle between the stylus and the lobject is less than about 45 degrees, your i tkatised points sometimes appear in unpredictable places, though this can be rectified m with a quick move operation. Keep the arm e mthin its more comfortable limits and it hardly t aver misses the target. r The arm uses sensors at each joint similar eto those used in robotics, and these sensors . need only keep a very careful eye on the Iangle at which the arm is being rotated. With ttas information, and knowledge of the arm's 'physical dimensions, working out the three s dimensional position of the stylus tip is a orelatively simple maths puzzle. nTRUE SIZE l The firmware on board the control box uses y real world measurements, so if you are digitis- w ing a model of a Spitfire which is only 15cm h icing you'll have to scale it up to its proper vir- etual size later on. This should be seen as an n advantage rather than a disadvantage, ythough, as it ensures the hardware Side of the oequation always knows what it's doing and, umore importantly. where. ' Once all lines have been digitised, you rshould be able to use Modellers Skin feature to e create a continuous surface across the rsplines, or the Patch option if you want more control e - though this is a trickier method The finished a model's quality and accuracy are affected l more by the user's skill at iudging where to take sample points and how many l samples to take, rather than the y accuracy of the arm. s This is the tricky bit, and t requires a fair r e t c h - amount of patience and practice. The use of plasticine (again, a small amount of this is supplied) or tape to stick a subject firmly to the digitising table is highly recommended, and any time spent marking off the grid and thinking about the best way to digitise each object pays great dividends, Be warned that you'll need a steady hand to get the most from Immersion - the arm moves very freely on its joints and can't be positioned 'hands off,' There's an optional foot pedal which can be used to leave both hands free when sampling points, but I found that stomping on this usually caused my hands to wobble at exactly the wrong moment, Apart from these considerations, there's very little to worry about when using Immersion, and only those with absolutely no dexterity will have any real problems. You'd have to be a dedicated and wealthy enthusiast to splash out on a peripheral such MAY 1995 The supplied macros ifIr kide several to hoip with alignment, but it's sliti very tricky when digitising an object In two part., then joining it Stole liennedii I110lf5 at — IMME151011 Per511l51 bligiti5er - and find5 317 PHOEINilE — 5110d-tilt to modelling heauen - as this. but tor many small companies and self-employed 3D artists the Immersion Personal Digitiser is a high quality, accurate tool which would quickly repay the investment through offering increased flexibility and cutting down on modelling time. It's just a pity we're going to have to send it back. py5 Es T 1 GRAPHICS Lightwave 30 software s yp The bottom line B E5 Fp ec T om i rn 11 . 1 ;d Product: - Personal Digitiser Imm Price: 1'1,5994-VAT (prices evarry ascco rrArg to a n y software or Amplements included) ion Supplier: Raytech BBS Phone, - Ease of use 8 0 1 Implementation 9 8 6 Value for money 8 Overall 2 8 8 3 2 0 0 0 II 1 -
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