Introduction

With the advent of new 3D games, many discussions started in the community of developers and programmers. These mainly centered on which graphical engine (meaning an environment or technology on which the relevant game is based) is good, what a href="Zaklad.htm#hardware">hardware (HW) is necessary, what resolution and how many colors are enough for the user. The biggest problem was to find a compromise between the engine quality and the HW price, on which it would run at an adequate speed. What would a high quality engine with true color be for if the game didn't run smoothly on the majority of PCs? The first breakthrough 3D game was WOLFSTEIN 3D. It was the first 3D game which ran well also on an already historical PC 286, 1 MB RAM equipped with the Trident graphical card. How was it possible? The answers is as follows: Wolfstein's engine used to the maximum extent all HW, but mainly used a method of calculation which accelerated calculations so that also on this 286/12 MHz it could run with a speed 20 and more images per second.

    The basis of every graphical card is the graphics chip. This has as its task all graphics operations, processing and drawing images. Because the graphics cards Trident (at that time the most frequent type) had no acceleration functions, all required calculations had to be done by the processor. Gradually over time, as processor development progressed, it was necessary to start developing non-professional HW devices enabling also a ordinary PC with a ordinary processor (then it was a Pentium 100 MHz) to achieve good performance in the field of 3D graphics. In developing a 3D accelerator, it was necessary to consider the following features: The card has to comprise all functions of a ordinary VGA card, as well as the 2D GUI accelerator functions (e.g., WIN 95 and more, for example display window shifting through hardware), functions for accelerating 3D graphics and extending video files also with HW support of replaying digitized video in the formats AVI, MPEG 1, and MPEG 2. Besides all this, they had to have available the required 2D power in the standard DOS modes VGA and SVGA. Because it was rather impossible to meet all these requirements at this time, the first cards had only some of the required features.

18.2   Basic attributes of graphic cards

18.2.1  Speed, speed, and speed

   Speed is one of the essential features of every graphic card. The majority of users expect a new generation graphics card with 3D acceleration to render 2D and mainly 3D graphics in amazing detail, but mainly, with high speed. The speed of a game is achieved through a higher number of pictures per second (or higher number of Frames Per Second, FPS). As an example of the importance of speed is the fact that many holders of 386s and slower 486s played Doom with details set on 'low'. Also then at the cost of lower quality graphics. The speed of 2D graphics is given in mega pixels per second. This represents how many pixels a given card can draw .The speed of a 3D engine is normally given in million pixels per second (Mtexels/sec), or in polygons per second. This figure represents the number of polygons that the 3D graphics chip can read and display per second. To use the 3D functions of graphical cards it is necessary that there is also a software application implemented on the HW basis that can utilize all this. For this purpose we have the interfaces: OPEN GL, DIRECT3D , and GLIDE. If a 3D accelerator is missing, then the processor must calculate everything, which means a massive drop in speed and quality.

    An important feature of the speed of graphical card is the frequency per second (FPS), or the number of images per second. Considered as excellent is a speed of 30 or more FPS, where the game is really smooth and rapid, on the other hand about 90% of players are satisfied with a value of about 20 FPS (e.g., 19-25 FPS). The speed of a game from the view of calculation is affected by its 3D geometry, the determining of the position of an object in an area, as well as by the actual rendering of the object on the screen.

18.2.2   Quality

    A professional user nonetheless expects from a graphics card hi-end performance in 2D GUI, at the same time maximum acceleration of 3D graphics with high resolutions (1024*768 and more), together with the maximum hardware support of OpenGL, whereas an ordinary user expects more detailed 3D graphics with a lot of polygons, fully textured, and all this with sufficient speed. A typical example is the graphics chip Permedia 2, which is intended for professional users, whereas for games it is practically unusable. On the other hand there are the graphics chips VOODOO 1,2 and 3,, which are primarily intended for game applications; they have only 16 bits of color and the size of texture is limited to 256*256. The current graphics cards (except the VOODOO chips) can render problem-free graphics in 32-bit color depth (per one pixel) and high resolution (800x600 and more).

18.2.3   Price / performance

    A graphics card must integrate many functions: quality 3D acceleration, support of a maximum amount of HW implemented functions, also 2D GUI acceleration, HW support of video replay, and reliable running under DOS, options of memory extension of the card itself, HW support for replaying MPEG1, 2, and DVD, possible TV-out. In the case that all these functions are to be connected to a low price, it is necessary that the number of integrated circuits in the chip is the smallest possible; the best is if just one circuit can manage all these functions. In general, it can be said that the more powerful a card, the higher its price.

18.2.3   How much RAM it is required for a graphics card ?

It is an unwritten rule: the more RAM the better. However, is extending RAM, which means a new investment, reasonable, and is it worth it? For using a 14-inch SVGA monitor in 2D, it is enough 1-2 MB RAM on the graphics card. However for 3D, the demand for RAM is several times larger. Therefore, it is necessary to count not only with the memory for graphics rendering but also with the z-buffer and for texture storage. On a 4MB 3D card, there is a maximum of 800x600, but if you want to have, in addition, also a 32-bit z-buffer, and the textures of 2048x2048, then you can purchase also a 16 and higher MB graphics card.

If you have a 32 MB card, you can allow double buffered 32-bit rendering in the resolution 1600x1200. With a 128 MB, you can go to still higher resolutions, and still you can have your z-buffer and double buffering. A 8MB card does not enable you to have a 1024x768 with 32-bit.
The free memory is used for storing textures, which are to be processed. It is an advantage if the card can compress textures (e.g.,   Savage, GeForce, and other) by which it uses available memory so that the textures do not have to be stored in the main memory. With a 32 MB card and in the resolution 1024x768x32bit, about 20 MB is free, and in case of the compression 1:8, about 160 MB of textures can be put in this memory, working on the assumption that a game has this amount of textures. It does not always have to be true that the more memory the better the card. The size of the RAM in a graphics card does not determine as a whole the overall performance of the card. On the other hand, for instance the THT with 8 MB of RAM runs rather slower than with 16 MB RAM, but the SAVAGE 4 with 8 MB runs almost the same as with 32 MB RAM, providing that it uses intensively the whole RAM of the graphics card.

Comparison of texturing power through AGP:

  • AGP 4X - 40 fps
  • AGP 2X - 30 fps
  • AGP 1X - 17,5 fps


Tests na :  http://www.mercury.org
 

18.3   Review of performance 3D graphics chips

Overview of the parameters of individual chips