|
|
 |
 |
 | | | | |
 |
|||
 |
||||||
          |
 |
 |
||||
|
That's No Moon… Back in the days when our gaming worlds were as flat as the screens on which they were displayed, the problems of creating beautiful and interesting 3D spaces seemed about as remote as the likelihood of Michael Jackson marrying Elvis' daughter. But as we now know, things change, and today's videogame artist has to be ready to build mesmerizing backdrops to suit a whole variety of 3D gameplay. The limits imposed on the artist most often relate to the hardware on which they are intending to run, as well as the software that is being employed to power the visuals. Ranked highly among these limitations are those of polygon count and texture memory. It's true that the number of triangles per second that can now make it to our screen seems to be inexpressible without the prefix "giga-". But as the reality of next-generation hardware confronts the hype, artists, despite the fact that the graphical power we now enjoy has increased exponentially, will continue to demand more. A similar (if slightly less spectacular) increase in texture handling has also taken place. No gamer's PC would dare show its face today without at least 16MB of dedicated RAM on its graphics card, and AGP technology has blessed the desktop machine with plenty of texture storage and retrieval power. Consoles too are getting the texture message. The Dreamcast is showing the way with its excellent compression capabilities, but once again, more is never enough, and compromises still have to be made. In the quest for beauty, when is it better to use polygons? And when textures? First, you need to speak to your programmers. I know that the conflict between code and graphics can take on biblical proportions, but unfortunately there is no substitute for good communication between the two departments. The restrictions of the engine coupled with the demands of your game will tell you, for instance, that in areas where 16,000 undead Samurai are set to attack in unison, you need to keep the background polygon count as low as possible. Your programmers should also give you some idea of any texture constraints you need to be aware of. There are, however, some general points that you may wish to consider, and that is where the "Death Star Principle" comes into play. Yes, I'm sure that you think I'm just forcing a Star Wars analogy in here because I'm a sad child of the 1970s and find it hard to be metaphorical without resorting to Mr. Lucas' monumental work. Well you're right, but bear with me for a moment while I explain. For the purpose of the illustration I'll assume that you're familiar with the Death Star. Throughout Star Wars, we see the exterior of the Death Star from three basic distances: long-range, approaching the surface, and "in the trenches." Looking carefully at the long-range shots of the Death Star, we get the impression that the surface of this immense sphere is some kind of ordered man-made structure. These shots, needless to say, generally use a matte painting and are not simply a highly detailed model seen at a great distance. As we approach surface of the Death Star, we swap to a detailed model of the terrain, which is designed with specific reference to the kind of shots anticipated, including camera distances, camera angles, and the speed at which the ground passes. Inside the trenches, we have yet another level of detail, contingent once again on the requirements of the shots to be filmed. Of course, it would have been a huge waste of time and effort to take the largest of the Death Star models and build in the kind of detail that was ultimately required for the trench run. Primary resources of time and money (as well as common sense) dictated that the detail be placed where it would do the most good, and that as long as the illusion of a credible whole was maintained, the viewer needn't ever be aware of the relatively bare patches in the distance. If we take this idea, and add to it the limited resources of both textures and polygons, the same rationale holds true for computer graphics -- put the detail where it has the most impact. Some general points on textures and triangles: 1.
One of the most important things to remember when building a game environment
is that it is going to be viewed from a player's position most, if not
all, of the time. Details the player is unlikely to see, or get close
to, can be kept to a minimum. If you find yourself building a cathedral-sized
interior with a ceiling that's 200 feet above the player's head, you
will most likely be wasting polygons by modeling stone carvings into
the tops of the supporting pillars. You will also be wasting texture
space if you put a 256x256 texture in a place where the maximum size
it will ever appear on the screen is 32x32.
3. Textures that aim to fake surface features should not as a rule contain too much information about the direction of light. Normally, the eye is inclined to accept that the main light source comes from above, so unless you are working on an area that contains very specific light information, make general textures gently lit from above. The concave/convex example, that you may be familiar with, demonstrates this:
4. Making something look realistic is usually easier with textures than polygons. A cube can be a convincing crate with the right texture, whereas adding an extra 200 polygons will have a strictly limited impact.
Perhaps the biggest challenge to those whose job it is to make games pretty is the creating convincing and attractive landscapes. Interiors are in many ways a walk in the park when compared to the task of producing great visuals for, say, a walk in the park. Why don't Unreal and Quake encourage you to roam freely through hills and valleys instead of jamming all 16 of you into a set of cramped corridors punctuated by the occasional medium-sized room? Is it because the proximity of Nature's beauty would incline the player towards gentle discourse as opposed to guided thermonuclear annihilation? I think not. O.K., gameplay has something to do with it, but I would suggest that keeping a meaty frame rate amidst a reasonable amount of action is a whole lot easier if you're in a confined space that has walls, a floor, and a ceiling, and at most, the odd walkway. You see, the problem with the outside world is that it just doesn't know when to stop. Size matters in computer graphics, and a lot of space means that there's a lot of stuff needed to fill it. It is also fair to say that the great outdoors tends to be full of things that were specifically designed to make their transition into your game world as painful as pair of barbed-wire underpants. You will however, be glad to know that this article is not going to give you step-by-step instructions on how to make a lifelike Canadian elm in as little as 12 polygons, I'm just going to talk about the ground itself. If you can, think back to the heady days of Acclaim's Terminal Velocity, when all it took to impress was a rudimentary 3D landscape with three texture divisions (snow, rock, and vegetation). In the 21st century, we find that our expectations are somewhat higher, so what do we do with all of that ground? First, let's return to the scale dilemma. This is when large areas are either textured to look good at close range, risking a very noticeable repeat in the tiling at a distance, or just the opposite, where the texture looks good from a long range, but is a blurred mess close-up. This problem is most often encountered with exteriors, where nature tends to make its terrain from large areas of rock and grass that stretch off into the distance in all directions. What can we do to maximize the attractiveness of our landscape, without having to create hundreds of cleverly interchangeable textures that may provide variety, but obliterate storage space? One obvious solution is to design your world so that it has no vantage points from which you are able to view miles of terrain, thus cutting down the player's opportunities to see how barren and monotonous your ground really is. This is certainly not feasible for some types of game, but can be perfectly acceptable when used appropriately. However, once this kind of ploy becomes intrusive, it starts to belong in the same category as those fight scenes where the baddies only attack in ones and twos, despite the fact that there are 27 of them ready for combat -- it's just cheating. Nevertheless, clever design is always important, but the more you restrict the player, the less impressive your world will seem, especially if they feel cheated by your artifice. So, if we really must deal with a lot of ground, our first and probably most familiar option is multi-texturing. God bless those that gave us this power. In multi-texturing, we have both a solution to the scale dilemma and a method for providing variety (or apparent variety) to the surface of our terrain without resorting to mass texture bombardment. Overlaying a texture whose scale is set to look good at close range, with another that has a much larger scale, will, if the two are blended properly, give the appearance of a continuously changing texture that is detailed enough to withstand close-range scrutiny and also holds up when viewed from a distance. Add this to a careful transitioning between a few well-chosen textures, the variety of ground cover that can be faked is quite impressive.
It would be remiss of me at this point not to mention procedural textures. While the whole procedural texture thing has begun to make an impression in the game world, unfortunately for those of us who laughingly refer to ourselves as artists, the power of all things procedural lies with the boys and girls at the programmers' end of the evolutionary ladder. It has its supporters and its detractors, but within the constraints of this article, I suppose it is fair to say that if you like the look, talk to those with the power, and see if it's an option. On a smaller but still useful scale, the way in which a texture is applied to a surface can also reduce the obvious tiling effect. Examples A and B both use the same texture, applied to the same strip of geometry.
In example A, the texture is applied so that it maps in line with the edges of the surface. In example B, the mapping is applied diagonally across the surface. In A, the repeat is much more obvious. The eye follows the edges of the geometry, and can easily pick out repeat features in the texture, as they are evenly spaced in the direction of these edges. Using a diagonally mapped texture, we are, in effect, lengthening the texture by aligning it so that any features that can be seen as repeating are spaced out in what appears to be a less regular way. This technique is not particularly complex or clever, but in certain spaces (and, it must be said, only with certain types of texture), it gives us a bit extra with no cost to resources. ________________________________________________________ |
|
|
Features
