The Texture Mapper

The procedure of texture mapping has always seemed to me most attractive because of its obvious complexity, its arcane sense of mystery and the fact that to produce one requires incredible patience and a little knowledge of the correct method of constructing 3D engines. I have experimented with simple textures from the beginning: even my first effort, using BGI graphics, gave the polygons a semblance of texture by shading them using the standard BGI routines. Later I started to endeavour to give the polygons the vague appearance of a given image, whilst maintaining the speed of my polygon code by only writing in optimised assembler. Soon after this point, however, I realised that chance experimentation was futile: a methodical approach was required for true texture mapping, and no subtle shortcuts would give the sense of tangible solidity that genuine texture mapping gives. Again, I began to systematically considering the process of texture mapping; and it is this process which I am going to attempt to document here, as well as producing a record of my eventual success. It should be noted that I have absolutely zero knowledge of the correct, conventional or accepted method of texture mapping; and there is no guarantee that my method is the fastest or the best optimised. I devised it purely on my own intuitive reasoning, and an ordered approach to the problem; and on the terms on which I designed it, the texture mapper now functions. Hence, first for consideration is the problem itself; what is texture mapping, and how can it be symbolically represented in a 3D engine? Texture mapping is, as far as I understand it, the mapping of an image, usually of fixed size to aid optimisation, onto a mobile polygon that can be plotted as part of a 3D engine. If it works correctly, the texture itself should appear to move and scale in 3D realistically, and hence allow far more life-like objects to be represented in the engine. The polygons must be completely mutable, to ensure their flexibility withing the engine; and in addition, the texture should be associated with the edges of the polygon as if it were a 3D object; that is, the edges of the texture remain in contact with the same edges of the polygon, however the polygon is rotated or manipulated.