Computer-aided visualization can at its simplest mean two-dimensional picture modifying with the aid of such software as PhotoShop or Fractal Design Painter for example. Generally, though, visualization entails a three-dimensional model which frees the object under observation from the restrictions of a given viewpoint.

The 3D model of the Central Terminal was created with AutoCAD and 3D-Studio software. The basic data included normal plan drawings, sections, elevations and detail drawings made with either CAD programmes or by hand.

This model was chiefly adopted as a working model for the viewing or critically important details in the design at the level of accuracy corresponding to a CAD drawing. The existing 3D model can be applied as a design tool even by users relatively unfamiliar with the finer workings of the program. In practice, the only requirement is that the user knows how to move the camera to desired point in the model for virtual viewing. The choice of target for observation as well as viewpoint is no longer limited to single one, since their computing can be left for the local network. The computing capacity which may be available in the net can thus be exploited, or the task can be left for night time.

Compared with conventional model viewing, the only restricting factor with the computerized model so far is its slowness, while on the pro side there are accuracy and the possibility of viewing in actual scale. 3D models can be divided roughly into four different categories according to the time and level of sophistication required: working, promotional, marketing and animated models.

The main point about a 3D working model is the facility it offers for the manupulation and revision needed in the design projects. In practice, the actual model is a composite of several individually created parts, which are then brought into the master model as separate objects. Depending on the use the working model is meant for, the image rendering can be performed even with relatively simple material and lighting conditions.

The promotional model should depict the finished building with the greatest possible detail already at the design stage. The updating of the model in a project of this size is quite time-consuming, since the designing proceeds at a different pace in different areas. Even the slightest of changes, for example in the placement of a partition wall, can cause changes in the 3D model not only to the partition itself but also to the definition of floor finishing materials, suspended ceiling structures and potential wall finishing materials. With large-scale interior models, the problems of lighting often have to be resolved at the level of an individual object, which means that any major changes to the parts can result in the readjustment of the entire lighting balance. Therefore it is advisable to consider carefully how often the model is altered or supplemented. On the other hand, if the model is not adjusted according to the changes in design, its value as a designing tool is clearly diminished.

The surface materials and lighting conditions of the promotional model should correspond as accurately as possible to the final product, even if the actual lighting and colour design were still waiting to be finished. In modelling, the creation of finishing material together with lighting design can easily take up a third of the entire time spent on the visualization process.

The model intended for marketing purposes is further complemented with the trimmings required in each individual project, such as adverts, actual furnishings, etc.

The animated model of a large target is structurally the most demanding, since continuous optimizing is necessary to bring down the computing time and the post-processing of images is limited to the fine-tuning of the colour properties by means of video editing software.

The computer animation is a composite of individual images whose size and number per second depend on the application purposes of the animation. Simple animation designed for viewing on screen only can consist, for example, of AVI, FLC or MPG type files the size of some 320 x 200 to 640 x 480 pixels. To achieve a reasonable likeness of movement, the minimum of 15 images per second is required. In a professional animation suited for video recording the image size must be 768 x 576 pixels and the image rate 25 per second (PAL system).

The image computation must further involve so-called Field rendering, which utilizes the image merging currently used in state-of-the-art video technology. The result is a very smooth and easy-flowing illusion of movement as the images are synchronized with the monitor's image updating.

The promotional animation for Phase 1 of the Central Terminal was made in 1995. The technical requirements were set on a par with the quality of a BetaCam video image.

The animation project was taken up already at the first stages of the modelling work but was somewhat pushed aside as the size of the model began to grow out of proportion, thus increasing the rendering times to a level quite unmanageable for the purposes of animation computation. The size of the model had by then already exceeded 800,000 3D faces.

The rendering of a single image with PAL resolution using a then state-of-the-art microcomputer took over a hour, exclusive of Field rendering at that. As the object was to create an animation lasting 6-7 minutes, in other words consisting of 9,000 - 10,000 images, the designers were faced with a severe case of optimizing and compromises.

In the end, they managed to bring down the rendering time to just over 15 minutes on average: the computing involved, though, cound take up the simultaneous use of a total of twenty Pentium microcomputers in three different locations with local networks. The resulting images were recorded on MotionJpeg format using a PAR card (Personal Animation Recorder) on a computer hard disk.

The size of the animated sequences, with the aid of Mjpeg compression utility, was some 1.2 gigabytes. The first editing session was performed in a video studio using digital techniques, and all subsequent editing was done entirely on PCs, with Adobe Premiere 4.0a software.

For the visualization of Phase 2, the software employed will be the 3D-Studio Max, together with the older Classic version. This older version is highly suitable for general viewing of a 3D working model since it does not require very sophisticated hardwate; whereas the qualities of the Max version are needed for photorealistic modelling of the ever-growing model and the creation of animated sequences.

It has to be noted that the animation of Central Terminal was done during 1992 - 1995 and the technology described in this practise represents technology at that time. Since 1995 this technology has improved.