Advanced Lighting Tutorial

Cse459 Preproduction for Digital Animation

Lighting Concepts for Environments

Guidelines for Day Lighting

Daytime scenes should generally be low in contrast, with nice soft illumination in shadowed areas. There are three basic lights that you should include when thinking about lighting a day time scene; a light that will represent light directly shining down from the sun (Key), a more diffuse type of light that will represent ambient “sky light” (Basically a Fill), and finally there should be some indirect light that is being reflected or bounced off/around various objects in the scene.

For the key light or sun light, the best types of lights are directional or spot, generally some sort of yellow in color. Both directionals and spots have their advantages. Directional lights are great because they cast nice parallel rays of light and subsequently parallel shadows. This mimics reality because if you look outside on a sunny day, you will see that since the sun itself is so far away, the shadows that are casted appear directly parallel and do not diverge as they get further away from the object as you would normally get with a spotlight that illuminates with light rays that radiate outwards from a central point. However, if you set up a spot light with a strong intensity that is far enough away from the object with a narrow enough cone angle, you can get the same effect as a directional light, plus some extra control.

The sky or fill light can essentially be a copy of your key light, but with about half or a quarter the intensity, and a blue color to neutralize the yellow color of the sun. The stronger the fill light, the more evenly the scene will be lit for a more “cartoony” look. To start off with, you can usually place this light 90 degrees away from the position of the key to provide a nice even fill.

The last type of lights should be the “finishing touches”. Look at your scene rendered with both the key and the fill, and see what areas need some bounced light to make the scene more believable. These can generally be spot lights, but you can experiment with point lights too! You might also want to think about which objects are reflecting any lights. In real life lights bounce off of everything around them. Lights also pick up color from the objects they bounce off of. For example if you are lighting a scene with a red wall and white floor and the key light is hitting the red wall, you might add a red spot light that points from the wall to the floor to simulate how that light would bounce in real life. Here is also a good place to play with the decay setting in your controls to get realistic fall-off with distance.

Keep in mind also that the overall tint of the final render may require that you play with the color and intensity of the key and fill. If your scene is being shot at sunset or late afternoon, an orangish tint might be desirable, while a blueish tint would be more appropriate for dusk or an overcast day.

Day Scene - Notice how in this photograph, the color of the sky (blue) is illuminating the shadows. There is that nice soft illumination going on in the shadowed area of the door and chimney that gives this scene low contrast. Also notice how the blue shadows balance out the yellow tint of the source light to give the scene a sense of balance. Additionally, the usage of the shadow of the tree is no accident; this scene would have been pretty boring had that shadow not broken up the lit side of the building. The shadow creates a source of interest and adds natural variation to the light in the scene.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reflected Light- Light will carry color from one object to another. Notice how the light coming in through the window picks up the brownish color of the venetian blinds and casts it on the white wall.

 

 

 

 

 

 

 

 

 

 

Guidelines for Night Lighting

The same general principles that apply to lighting a day time scene also apply to a night time scene. Its best to start with the same three light system, with moonlight replacing sunlight, but similar sky or fill lights and more indirect lights. However, one important thing to keep in mind is that moonlight is much dimmer than sunlight, so be sure to adjust the brightness accordingly.

Be careful when approaching the overall look of a night time render; naturally you may tend to think that a night time scene is really dark, but instead of making the image darker, try adding more contrast. Use weaker fill lights in relation to the fill lights, and if there are a lot of shadows in your scene, make sure not to leave them black! Use subtle cool colored indirect lights to give your shadows extra depth; it is best not to change the actual shadow color from pure black. Setting the shadow color to anything other than black brightens the shadow, because it is letting light partially leak through an opaque object, which can often create an unrealistic looking scene. This is due to having a shadow that is visibly lighter than the unlit side of the object (the side facing away from the light.) For example, if you have a blue tint to your shadow, but no blue light appears on the unlit side of the object, the shadow seems detached from the object.

Night Scene - This photo is a great example of night lighting. Its definitely not a dark image; instead, the shadowed areas are simply darker. You will notice rain or wet ground surfaces in a lot of films and photographs shot at night; this is due to the fact that water reflects light, adding more illumination to the scene. The fill lights here are much more subtle and create the high contrast look desirable for nighttime scenes. In general street lights/manmade lights will often appear very warm compared to the blue tones of natural light, especially at night.

 

Shadows

There are two types of shadows that can be calculated by Maya; depth map shadows and raytraced shadows. Both have their advantages and disadvantages. The best thing to keep in mind is that depth map shadows are very quick and efficient to render but need tweaking to look the way you want them to, while raytraced shadows look great but take up a lot more memory and render time.

If you are using depth map shadows, make sure that they are powers of 2 (512, 1024, 2048, 4069). The second thing to consider with depth map shadows is correctly framing the object you want to cast a shadow (if you are using a spotlight); if you have a huge  angle with a lot of empty space around the object, you will start to notice artifacting and other inaccuracies in your shadow because the samples of the depth map are spread too far apart and wasted in all the empty space. Try pulling the spotlight out and narrowing the cone angle for a tighter fit around the object. If you have a huge scene with a lot of objects that would be hard to frame within a narrow coned spotlight, try using several different lights to replace one big light (little variations in your lights will seem natural anyways), consider doing a separate shadow pass, or a shadows only light (discussed below).

 

 

Sometimes you will want to cheat or fake a shadow where normally there wouldn’t be one, or you want to have more control over the shape and position of a shadow in relation to an object. This is where negative lights and shadows only lights will really come in handy. Negative lights are any light with the intensity set at a negative number so that instead of emitting positive lights (brightness), they are emitting negative light (darkness). These can be great for darkening areas like corners of rooms, underneath furniture, etc etc. Volume lights are especially awesome for negative lights, because it affects everything equally in a set radius, so you can evenly darken everything in a selected region. Shadows only lights are lights with the light color set to black and the shadow color set to white (opposite of default settings), and the intensity turned to negative. These are extremely handy when you wish to add a shadow to a scene without adding any extra light into it. Personally, these are my tools of choice for adding contact shadows if occlusion is not being used, or sometimes even along with occlusion.

Light Linking

Linking lights is EXTREMELY helpful when you start lighting a scene, because you can specifically control exactly what light illuminates what object. There are two ways to do this; either by using the light linker, or manually by selecting the light, then selecting the object you want illuminated, and clicking on the “create light links” button in the lighting/shading menu. Make sure you have “illuminate by default” clicked off in your light options. Similarly you can break light links by clicking on that option.

As you start adding more and more lights it can get confusing exactly how every light in your scene is affecting the scene. You might think one light is doing one thing but its actually doing something else. There are two good ways to figure out what your lights are really doing. You can hide all of the lights in the scene except for one and render. Then you will be able to see exactly what that one single light is doing. You could also check to see what a few lights are doing at a time by setting their colors to different saturated colors.

Cool Gizmos and Gadgets

Gobos

As some of you have already experienced with the fruit bowl assignment, gobos (or cookies) can lend some great visual variation in your scene. They can break up a light or project a pattern, such as leaves on a forest floor to simulate light filtering through the canopy. You can choose to approach this traditionally, with an actual object in front of the light, or you can map an image into the light’s color channel which will achieve the same effect with less mess.

Barn Doors

There is a barn door option on spotlights which will allow you to crop light horizontally or vertically, limiting the coverage of that light to less than its natural cone angle (great for light coming through windows!). To view the barn doors, click the Show Manipulator Tool button from the toolbox to see the light’s manipulator (or press the hotkey t.

Light Fog

Light fog can add really neat atmospheric effects into a scene, and can also simulate dust, steam etc etc for whatever purposes you need. This option can be found under the light effects controls in a spotlight. Clicking the checkerboard to the right of the Light Fog option will create a new shape node lightFog1, a new blue cone that will appear in your viewport. Make sure that you adjust the size and scale of this blue cone, because fog will only appear within the interior region of the cone. By scaling the spotlight itself, the cone will scale along with it because it is a child of the spotlight’s transform node. To avoid hard edges, I generally like to have the cone of the fog extend beneath the ground plane so that its all nice soft fog, since the cap of the cone cuts off very abruptly. Now you can play with the intensity and spread of the fog to achieve a look you like. A high Fog Spread value produces fog with uniform brightness shooting out from the cone of the light, where a low Fog Spread value produces fog which is brighter at the center of the spot light beam and foggier at the end. Fog intensity just controls the brightness of the fog, with brighter fog having a higher value. You can also map images into the color and density channels found under the lightFog1 node to produce a less evenly gradated fog.

Environmental Fog

Environmental fog simulates the effect of fine particles in the air (for example, fog, smoke, dust). To set this up, go to your render settings, click the Maya Software tab, and then scroll down to open up Render Options. This is where you create Environment Fog (we will be using Simple Fog); a new node will pop up, envFogMaterial, and will have two major attribute settings you will want to play with. Color just changes the color of the fog itself, so you can simulate smog (brown) etc. There is also a control for Saturation Distance, which measures the distance from the camera at which environmental fog becomes fully saturated (that is, its color value reaches the color setting).Saturation Distance affects how much objects within or behind the fog are obscured, so the higher the number setting, the more the fog will obscure the objects. Some other useful controls are Blend Range, which measures the vertical distance over which environmental fog gradually fades from full density to zero density, the Min and Max Height, which measures the minimum and maximum height from the origin within which the fog exists, and Use Layer, which you can use to assign a texture to the Layer attribute to create variation in the density and color of your fog.

Distance Fog - Objects far away from the camera will appear much less in focus, and this effect of distance can be helped along by adding environment fog. In this photo, we see that the fog gets thicker the further it extends into the background. The blue tint to the fog also helps create the illusion of distance; generally, warmer colors will appear to pop out in the foreground, and cooler objects will recede into the background. Try looking at two identical objects side by side, one blue and one red, and you will see how the red object seems in front of the blue one!

 

 

 

 

 

 

Setting up Render Globals

In the "Common" tab:

Under "Image Size":

Under the "Maya Software" tab:

BEFORE SENDING YOUR RENDER TO THE FARM, TEST A FEW FRAMES IN MAYA! Just to make sure your lighting is working and stuff looks right.