Chargement en cours...

Unreal Design | ModAddict | SG Special Unit
Bienvenue sur Unreal.fr ( Connexion | Inscription - Pourquoi ? )
#unreal.fr Stay Tuned !

# Lighting – Part 3: Special Cases

Mapping
Auteur : Gui (translation: ArcadiaVincennes)
Jeu concerné : Unreal Tournament 2004
Lighting – Part 1: Theory
Lighting – Part 2: Application
Lighting – Part 3: Special Cases
7) Exterior Lighting:
With UT2Kx's introduction of the Terrain tool for modeling the ground, more and more exterior levels were born, hence the necessity to provide level designers with the appropriate tools for this kind of level. Here, the actor we are most concerned with is the Sunlight Actor: this must be placed in the Skybox, and will thus illuminate the level only through the BSP surfaces set to Fake Backdrop. Therefore if you do not see the light after having placed the actor and Built Lighting, then there's a good chance that the problem comes from either the actor being in the wrong location, or the flags on the BSP are set incorrectly.
What's the difference between a normal Light Actor and a Sunlight Actor? The first has a limited range, but lights in 360°. The second has an unlimited range but lights in only one direction: the rays of light it generates are all parallel and, therefore, all its shadows are as well. Just like a StaticSpot, it will need to be pointed in a specific direction. That's all. Even though their differences are small, their results are spectacular and extremely practical. Whereas in Unreal 1 and UT99, the designers had to fight with numerous Light Actors, generally with LE_Cylinder and bDirectional = True, in order to direct them in a specific direction, it is possible now to only use one. The time savings is therefore considerable.
You can, of course, and to some extent it is even expected, use each of these actors according to their specialization. Just because a level has a sky doesn't mean that the light 'falling' on the level must come from a Sunlight Actor. (Yet, now that I think of it, is the light from a sky obliged to 'fall' on a level? Is there a reason other than pure realism to avoid creating a level where the light comes from under the players' feet? I'll let you develop that idea: an inversion, the basis of all sorts of contrasts from a certain point of view, is often a great source of creativity). People who have spent a long time designing with UEngine 1.0 often have a wide palette of techniques at their disposal because they've had to learn how to circumvent the difficulty of the lack of a Sunlight Actor. Rogelio Olguin, alias Desperado#2, gives us a brilliant demonstration of not using the Sunlight Actor in DM-1on1-Desolation:
This level, a completely spectacular and vibrant testimony of a real talent, is entirely lit with the 'old-fashioned' method. In spite of the many views of the imposing Skybox, you will not find any Sunlight Actors here. Why did the author ignore a tool as practical, as precise and as reliable? Because the author, I believe, illustrated his particular gift by preferring to 'draw' the shadows himself rather than allow a machine to do it for him. The Light Actor, which is in the area above the wide picture window, lights in all directions, although not exactly since its property assigns it to a LE_Cylinder. However, the fact that its shadows are not exactly parallel makes it possible to introduce more subtle shadow effects, despite being less mathematically exact compared to that of a Sunlight Actor, in this area. Of course, another reason also relates to the propagation of the windows all around the map: it was impossible for the author to use a Sunlight Actor without avoiding a huge headache. Thus an author who knows what they want in terms of architecture manages to circumvent their lighting problems with a simple solution, the best one of all. It is worth noting that the attitude of Desperado#2 is the opposite of that which I described at the beginning of the tutorial. Namely, that it is necessary to think about the architecture of a level according to its lighting and not the reverse. However, this wasn't the author's first try, and I believe I've already told you that art is not an exact science.
Some tips worth knowing regarding the sun and, in general, light from the sky:
- It goes almost without saying that the position of the sun in the sky varies according to the time of day, the latitude, and the seasons.
- Since the Unreal Engine doesn't manage radiosity, Ambient Lighting is certainly expected in an exterior location, but is not necessarily essential depending on your control of the lighting.
- A simple Corona texture from one of the official texture packages is enough to represent the sun in the Skybox. It's not necessary to model a static mesh for the kind of 'detail' that few players will pay attention to; unless your level is located very close to a star or even on its surface.
- Sunlight is not White. Make it, instead, an off-White, pale Yellow where the Yellow dominates. This is the reason why one resembles a corpse when looking at oneself in the bathroom mirror under a fluorescent light, as they're generally completely White. It is also for this reason that painters worthy of the appellation always work with natural light and not that of a candle or, worse, a flashlight (this problem doesn't really concern you since you normally work with a screen where images are unaffected by ambient light, but it's still good to know if you ever try to express your creativity in another medium).
- Moonlight is almost the same color as sunlight since it is sunlight reflected off the moon and comes down to us; although I will admit it is a hair darker - taking into account the grayish color of the lunar surface. On the other hand, the quantity of light that returns to us is directly proportional to the moon's size: a half-moon will not reflect as much light as that of a full moon, for example. In all cases, however, it can never equal the amount of sunlight, for obvious reasons. Additionally, night environments are often lit by a Blue hue – probably because nights are 'fresher' than days – and it can be a refreshing change to bend realism and to use a lot of Blue to represent lunar light instead of lots of Yellow. But the choice is up to you in the end…
- Light from other planets and from the stars is practically negligible, but if your night is moonless, then it can be permissible to 'distort' the light to avoid having too dark a level.
- With cloudy weather, sunlight tends toward Blue – it darkens. Therefore, and especially so, shadows become more diffuse; a detail often forgotten. If it is an all-encompassing storm, on the other hand, then there is no risk in using a dark Grey.
- Various floating particles, that simple Fog can represent, will probably have an influence on the color of the sun; even tinting the light towards orange and even chestnut. Note that on our planet the color of an oxygen molecule (an azure Blue) affects most of the color of the sky and therefore significantly affects the color of solar light (in space, sunlight is more raw; see recent reports on space exploration for more details). As for extraterrestrial planets, well, it's your choice…
- At dawn and twilight, sunlight tends towards Orange, or straight up Red, much more than Yellow. It will certainly not be as pale as at midday either. The reason is due to the position of the sun in the sky and therefore the thickness of the amount of atmosphere the light must pass through. The more atmosphere, the more the light retains colors until nothing remains but the Reds (once again, these colors vary drastically on other planets according to the base color of the star – there could even be several – and the atmospheric composition of the planet involved). See the following diagram for more detail:
- And while I'm at it, it's the exact opposite for underwater lighting: light tends towards blue the deeper you dive; not because water is blue (it actually has no color at all: when you see the sea or the ocean as blue, you just see the color of the sky reflected on the water's surface), but simply because water has the physical property that absorbs Red…
8) Shadows: Some tricks worth knowing…:
Shadows are fundamental to create certain basic contrasts, therefore you can use them to 'dress' empty areas of your level; the principal advantage of this being that they do not require additional polygons or textures. Thus they are fairly cheap in terms of FPS while also removing potentially annoying flow blockers from the gameplay. It is the inverse of the process presented in the section devoted to the use of the LE_StaticSpot in DM-Oceanic above. Some examples:
Here, in DM-Leviathan, a quarter cylinder static mesh and a simple alpha-masked texture, seen to the right of the screenshot, allows the light from the Light Actor to pass through only in the transparent areas of the texture. This projects shadow effects which give this slightly plain corridor a more interesting aesthetic. Also note the effective use of 'Red Light' in this area…
In DM-DE-Ironic, see how the grid-shaped static mesh which decorates the floor with light projects a network of shadows dressing the floor and walls.
Even if this trick doesn't interest you, it is still necessary to adhere to certain restrictions both technical and artistic:
- The first relates to the 'weight' of Lightmaps. This is often over-estimated in terms of performance; the problem stems from, especially, the size of the total file and the implications thereof (download time, hard drive space, etc…). I thus recommend that you set all the surfaces you are sure will never be seen to Unlit (including Fake Backdrop surfaces).
- The quality of a shadow is inversely proportional to the size of the BSP surface on which it is projected: the larger a surface, the worse the quality of the shadow. Thus, try to keep to smaller BSP surfaces or, if you notice artifacts you don't know how to get rid of on a BSP surface, try reducing the size of the corresponding brush, for example by dividing it into different pieces. Thanks to djsilt, from what forum I no longer know, who helped me figure out this problem and who gave me the answer from which you can all profit now.
- The distinction of a shadow depends on the distance between the caster and the surface on which the shadow projects. You can experiment with this at your own home: place your hand under your desk lamp. You will notice that as you bring it closer to the desk, the more distinct the shadow becomes, whereas as you move your hand away from the desk, the shadow becomes fuzzier. You can simulate this by modifying the properties of the BSP surface's Light Map (in the Pan/Rotate/Scale property box). The closer the surface to the shadow caster, the lower the value will be – usually about 32. But be careful with this, first because of the problem indicated above, and second because sharp shadows are very rare in reality, even though some may find them very pleasant, and finally because 'cutting up' all the walls in the level into multiple BSP surfaces quickly becomes tiresome, and expensive in terms of polycount. It should be noted that the judicious use of Projectors makes it possible to obtain similar results without having to edit the properties of multiple BSP surfaces. For example, in DM-Compressed: on the left, the Projector as seen in the level, and on the right, its corresponding texture – note that the edges become fuzzy in order to simulate the distance of the gird away from the light source.
Changing a Light Map's properties affords us an excellent opportunity to more closely examine the compression algorithms of the images. Contrary to appearances, bitmap images are not 'square', but are simply a line of pixels. In an 800x600 image, for example, the image is a line that is 800 x 600 = 480,000 pixels long. The program used to view the image, when ready to display it, will count 800 pixels out and then will 'cut' the line at the 800th pixel and then continue counting again below the first pixel. It will count another 800 pixels again, and then will 'cut' the line again, drop down one, and start counting again until the last, 480,000th pixel. The render of the final image will consist of 600 lines with 800 pixels in each. If you've worked on very large images that are resource-heavy in the past, you may have noticed that when the image is refreshed after a change, it looked like lines of text propagating word after word. This is, in fact, exactly what occurs, the only difference being that it uses pixels instead of letters.
This 'line' in bitmap images thus allows compression algorithms to be created. A format like .bmp, for example, does not compress: the corresponding file retains the details – thus values of RGB, or CMYB depending on the color spectrum used – of all the pixels that form the image. A format like .jpg, contrarily, 'combines' the pixels that share the same color. If part of the image is white, the line of pixels stored in the file will retain only the color value of the first pixel. It will then declare the rest of the pixels in that line that are the close to the initial color the same color as the first pixel and will ignore the precise values of each individual pixel. An extremely simplified example:
In this case, the compressed format will retain only two pixel colors: White and Black. All the pixels the closely match the first white pixel will be declared identical to the first until the line arrives at the first black pixel. At that point, the change to black will be noted, and then that color will be assigned to all others along the line that are close to the initial black. As an experiment, you can save this image after having turned it 90°, and then save each of the versions of the image, both horizontal and vertical, in a non-compressed format. Compare the file size of each and see the difference.
The creation of custom materials is supposed to account for such advantages. If you create a skin for a static mesh, or a texture for BSP, try to exploit the compression algorithms in order to reduce the file size of the final image. I'm not trying to encourage you to create skins and textures made of horizontal patterns, but sometimes making a simple 90° rotation before saving can save you significant file size, with all the advantages that implies…
9) Various tips and shortcuts:
a) 'Pitch Black' (or completely dark):
This old trick consists of leaving certain portions of the map black in order to allow the spectators' imaginations to populate the darkness with what they want to see. The masters of the Dutch school of claire-obscure are the most well-known practitioners of this. In level design, the advantage is that it can save on details and reduce the resources used (like textures and polygons). The history of the FPS abounds in examples: for example, in the anteroom of the Skaarj queen in Unreal 1, or, more recently, many areas in Quake 4. In UT2K4, a good example can be found in the ceilings of CTF-BridgeOfFate.
And, since inversion is always useful to artists, the central chasm of the same map shows the same method.
While following inversion, which is the base of all contrasts, you can always replace Black with White (while being careful not to dazzle players too much). Thus, we see this in Rogello 'Desperado#2' Olguin's DM-CBP2-TelMecoMEX.
b) Coronas:
These objects are often confused with Lens Flares which one finds in the majority of 3D programs. Coronas are textures of light halos that one can assign in conjunction with a Light Actor to simulate the brightness of the corresponding source. They can add a hard to contest touch of realism, especially for those levels with humid or misty atmospheres, since such halos occur in reality, especially when ambient moisture diffuses the light immediately around the source.
Some specific tricks:
- Their influence on performance is not negligible. One corona per source is more than enough. If you misuse them, you will encounter severe drops in FPS, but you will obtain a touch of realism in return. For this same reason, don't feel obliged to allot a corona to each light source in the level: it's a trick, not an indispensable ingredient.
- Place coronas close to the surface of the light source and at its center. There is nothing more unreal (no pun intended…) than a corona floating in mid-air. Take the time to position the corona appropriately as regards the light source and not leave a gap between them. This kind of mistake is visible more often than one would think during a game… This being said, the use of coronas doesn't stop with light sources (this may be the glow a fusion engine gives off, for example…), thus for other cases it can be, of course, that the corona isn't touching anything at all.
- Coronas are not visible in the Skybox. You will thus not be able to use them to simulate the sun, the stars, or anything else. It will be necessary to place a corona texture on a brush or static mesh so that it's visible in the Skybox. On the other hand, you could use a corona to simulate the sun if it's in the level proper, instead of the Skybox. The result, while being rather spectacular, can sometimes be a little too dazzling. If so, then adjust the size and position of the corona so that the simulated sun gives the impression of being 'infinitely far'. This will not always be possible depending on your level because you'll want to avoid the potential for migraines in a detail that few players will pay attention to because it's a little 'too high'.
- By default, the size of a corona is fixed; i.e. its size on the screen does not vary based on the distance one observes it at. This can be annoying for players depending on the circumstance (they can easily dazzle, see the screenshot from DM-CBP2-TelMecoMEX above). In order to solve this, the developers added certain properties to coronas in UT2Kx: Properties light -> Corona -> MaxCoronaSize and MinCoronaSize which will enable you to 'fix' the size of the coronas to suit you. Having spent a long time in UEd 2.0 learning more about coronas than one would want, believe me, this trick is very practical, but do not misuse it; most of the time the default settings are completely adequate. Don't bang your head against it seeking absolute realism, you won't find it with this version of the Unreal Engine anyways.
c) Fog:
Fog is one function of the Unreal Engine that was greatly improved over its previous UT99 model. If many level designers overdid it on their first UT2K3 levels, it should be admitted that this function has many practical uses, both on the technical side, and on the artistic side. First, it can have a beneficial impact on performance, in that it hides assets from being rendered outside its radius. Second, for the realism it adds; objects become mistier and blend into the fog color as one moves away from them since the thickness of the atmosphere obscures more. Unfortunately, Fog is not always your friend. By removing some of the clarity, it can destroy contrasts and dilute colors, therefore ruining certain effects. Therefore use it intelligently because if a light fog can reinforce an environment's atmosphere it doesn't create it by itself.
Another problem with Fog has to do with the properties of Zones. If you create a Zone with Fog, and create a Zone without Fog next to it, when you pass from one to the other, the Fog will either appear or disappear suddenly. It will always be too visually brutal unless you use the same exact Fog properties throughout your level which can cause problems either early on, or later. You are supposed to be the Master of your project, not its slave; it is not the level that directs you – you control the level. Thus, you will find a very practical property in ZoneInfo Properties -> ZoneLight -> DistanceFogBlendTime. This makes it possible to control the time over which Fog will appear or disappear when entering/exiting a Zone with Fog. Adjust it according to your needs.
You can also use an intermediate Zone where Fog will become less important; kind of like a 'buffer' to a certain extent. This can be used to gradually increase or decrease the Fog between contiguous Zones by slightly adjusting the values in each Zone. However, this can quickly become a headache and will also send you back to using DistanceFogBlendTime usually. It goes without saying that you can, of course, mix these two methods.
Note: Fog present in one Zone will not be visible from other Zones. There is nothing you can do about this as far as I know. If you do come across a solution, don't hesitate to write me.
d) Lighting for Team-Based levels (CTF, DDOM, Br, …):
By now, you may have already understood why Team-Based lighting colors are Red and Blue: they are, quite simply, the opposite colors in the RGB spectrum.
It is rather common to use the dominant Reds for the red team's base, and the dominant Blues for the blue team's base, however, alternatives should be handled with caution. I've often seen levels where these colors are not combined in a very pleasing way. White can accompany Blue well; however, this is not the case with Red. Once faded, Red becomes diluted and functions 'badly' (once again, we return to the principle that Red Lights should only be used in the darkest corners of a level) when Blue is often already considered pale in our minds (a habit which probably comes from seeing the azure blue of the sky…). Therefore, I would recommend that you mix the Red of the corresponding base with Yellow, since Green would produce too strong a contrast, but nevertheless possible if the color chosen is not too strong but sufficiently pale enough to avoid clashing too much.
Additionally, it is not always necessary to use Red and Blue exclusively to color the bases of your Team-Based level. In the past, some designers have tried using different colors, and even played with textures (in particular, a level for UT99 called CTF-Times, the name of the author escapes me, knew how to exploit contrasts in such a way that, I believe, made some impressions). More recently, the multiplayer maps from Quake 4 clearly demonstrate that Orange and Green produce a contrast sufficient enough to replace Red and Blue, respectively. Do not hesitate to explore other possibilities.
You can play within the boundaries of the map theme too. For example, a twilight sun, thus tending toward Red, can use Orange and Red as a base color, whereas the opposite base, placed such that it is back-lit, could be tinted Blue and Green. Conversely, if the level is in orbit around a blue star, invert the situation where the Blue base is directly lit and the Red is placed in half-light.
e) The 'Lruce Bee' technique:
Lruce is an author for whom I have great respect. Not only are his works counted among the most successful in the community, (see DM-Victoria for UT2K3 if you still believe that only custom stuff can personalize a level) but he is also a human who could serve as an example to certain people.
The technique he developed consists of maximizing all the lights in a level (in terms of each Light Actor's Brightness) and then lowering their Brightness values gradually until an adequate lighting level is reached. This technique is the 'reverse' of the normal method – and it's useless at this point to elaborate on what I think of inversion. This makes it possible to avoid overly darkened areas with too-timid lighting despite an author's best intentions.
This unusual technique presents one problem for the beginner level designer: it very easily creates 'greening'. This 'greening' is a defect of the lighting system which occurs when a surface receives too much light. When this occurs, the surface becomes tinted with a particularly unpleasant greenish-yellow hue which has nothing to do with the colors of the Light Actor(s) that light it. Therefore, if this happens, adjust the Brightnesses of the surrounding environment.
Conclusion:
That's about all I can say to you regarding lighting in UEd to the extent of my knowledge. It goes without saying that this tutorial does not contain every possible and conceivable technique available. I just hope that you will have the occasion to retain two or three tricks which will be useful to you some day. If certain details were not very clear to you, or seem to deserve additional explanation, do not hesitate to contact me via pm on this forum, and I will try to make things clearer.
Now, launch UEd and get to work.
Return to mapping tutorials

accueil | plan du site | crédits | historique | contact | 4.2k7 - 2007