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Vladimir Nabokov

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Letters from Terra - Life in water warmed by sunlight
 
 

     
 
 

     
A demonstration of the power and subtlety of the SVGA graphics einge. Click here to see more about fractals.
 
 
     

Simultaneously, a more sophisticated graphics engine was being constructed from several others examples, with provision for a virtual screen, numerous geometrical routines, page flipping, and PCX loading. A seperate unit, Images, was designed for the loading, storage, and display of Canvas II images. These were then stored on 64000 byte buffers, allocated from the heap, and kept in the same format in whcih they were to be displayed: ie. drawn onto this buffer as if it were another virtual screen. A simple pascal routine could then transfer the image to the real or virtual screen by simultaneously scanning the buffer and the destination. This was still slow, but the increased flexibility of the engine allowed the construction of Faculty, which exhibits some much more sophisiticated imaging techniques, as well as some interesting game engine characteristics. The next important refinement to the engine occured, however, once the images were stored in a continuous stream in the file, allowing them to be blockread into the buffers and facilitating the creation of the image compiler and compressor, vital to reduce the large numbers of images into a single file as is the case in Trooper II. In the new engine, images were stored in a simple linear form in the buffers, which greatly reduced the space taken up (there was no longer 'white space' that could not be filled) and allowed a different combination of images to be loaded for each level, as occcurs in Trooper II, without complex routines to determine the position for iamge loading on the buffer. More complex procedures were then required to draw the images, but refinement of the pascal allowed this process to be speeded up to a point where full screen page-flipping animation was possible, and Trooper II could begin to be constructed. Over 200 images are included in the central image registry for the full game: the engine deduces which are necessary when each level is loaded, includes standard images that a required for all levels, and loads them nose-to-tail into the several graphical buffers reserved either in the conventional, XMS or EMS memory. A special routine was written to rapidly display the scrolling background, and images are invoked simply by their registry numbers when the engine requires they be drawn. I had effectively constructed the graphical template for a sprawling platform game: over a year of work was required to finish the engine, draw and integrate the graphics, tune the AI and write the level editor. Trooper II, with all its source code, is available for download in the Trooper II section of this site. One project still remained, however: the construction of a high resolution, SVGA graphics engine that was at least as powerful as the MCGA one I had already developed. There are many MCGA sprite engines available on the internet, and a few SVGA; even one BGI unit for that purpous; but very few offer the versatility of SVGA imaging that I required. It was obvious that to implement a similar engine, that was capable of entirely automating the five segment switching process that is necessary to access the entire SVGA display, I was going to have to use more power than Pascal afforded. I had already learnt some assembly language, but this was the largest test I put it to.

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Letters from Terra | Updated 15th December 2004 | By Jonathan Ayling