# how lighting works **general notes from different places. needs to be organized and processed. until then, here are the rough notes…** --- - [ ] Increase Ray Depth in Arnold Render settings. Explain why. --- ## LIGHTING TIPS FROM ALAN CHAN i) Ambient light down to at most 5%, 0% is best. This way you’re starting with an absolute clean slate. ii) Understand what each type of light does, how it lights the scene. iii) USE FALLOFF ON EVERY LIGHT until you learn how to break the rules. iv) You are lighting for mood, not for the audience to see the amazing detail and time that you put into your modeling. You are painting with light. You control what the audience sees and does not see (including the vertical and the horizontal). Once you get accustomed to it, you should also be able to determine the detail you need on any particular object in the shot, and therefore adjust your modeling accordingly. v) Shadows are as important as highlights. This means not only the position and thickness of the shadow but its quality as well - raytraced hardedges, or shadowmapped softedge etc.etc. vi) MOST IMPORTANT: LEARN TO LIGHT IN THE REAL WORLD. This information will benefit you to no end when lighting in CGI. If you don’t have access to equipment, check to see if your town or city has a cable local access program that you can join to learn lighting. Alan Chan—Digital Domain _Alan Chan is known for his work on The Lord of the Rings: The Two Towers (2002), Titanic (1997) and Harry Potter and the Sorcerer's Stone (2001) among many others._ [Alan Chan Credentials on IMDB](http://www.imdb.com/name/nm0150782/?ref_=fn_nm_nm_4) --- ## LIGHT AND SHADOW IN THE REAL WORLD In the real world, when light shines on a surface, the parts of the surface facing toward the light source appear illuminated, and the parts of the surface facing away from the light source appear dark. If one object is located between a second object and the light source, the first object casts a shadow onto the second object. In this lesson, you will learn about the different light types available in Maya that allow you to simulate natural and artificial lighting effects. ### ABSORPTION, REFLECTION, AND REFRACTION OF LIGHT The color of the objects we see in the natural world is a result of the way objects interact with light. When a light wave strikes an object, it can be absorbed, reflected, or refracted by the object. All objects have a degree of reflection and absorption. Note: In the natural world, light can also be transmitted by an object. That is, light can pass through an object with no effect (an x-ray, for example). These types of light, however, are not represented in Autodesk Maya because they have no visual effect. ### Absorption.  Light stops at the object and does not reflect or refract. Objects appear dark or opaque. Example: wood. ### Reflection on a smooth surface.  Light bounces off the surface of a material at an angle equal to the angle of the incoming light wave. Example: mirrors or glass. ### Reflection on a rough surface (also called Scatter).  Light waves bounce off at many of angles because the surface is uneven. Example: the earth (that’s why the sky is blue). ### Refraction  Light goes through the object and bends at an angle. Example: diamond (greater angle) or water (lesser angle) ### DIFFUSE, SPECULAR, AND GLOSSY REFLECTION Reflection is divided into three types: diffuse, specular, and glossy. ### Diffuse reflection.  Diffuse surfaces reflect (scatter) light in many angles. Diffuse reflection accounts for more of the color than any other type of distribution because most objects are opaque and reflect light diffusely. ### Glossy reflection.  Glossy surfaces are actually specular surfaces with micro surfaces at angles to surface plane. These micro surfaces reflect light not only specularly but also diffusely (at angles very close to the specular transmission), giving the surface a glossy appearance. ### Specular reflection.  Specular surfaces reflect light at the same as the angle at which the light strikes the surface. Specular reflection gives objects a glossy or mirror-like appearance. ### Diffuse refraction.  Diffuse refraction scatters light in many angles. #### Glossy refraction.  Glossy surfaces are actually specular surfaces with micro surfaces at angles to surface plane. These micro surfaces refract light not only specularly but also diffusely (at angles very close to the specular transmission), giving the surface a glossy appearance. Specular refraction.  Specular surfaces reflect light at the same as the angle at which the light strikes the surface. --- ### MAKING IT LOOK REAL The first thing you need to think about when trying to light something realistically is that this is not the real world. While there may be only one light in the real world (or two or three) you will need to add many more in the CG world. Unless you have an enormous amount of time & money you are going to have to learn how to fake reality (global illumination makes it look real in exchange for very, very long render times). You can establish the mood of a lit scene by carefully choosing a light’s color, position and shadow quality. Many lighting scenarios encountered in everyday life have specific looks that we are subconsciously familiar with. Additional lighting scenarios have been stylistically established by motion pictures, television, and video games. We will be working with a single room and will try to emulate a warm sunset, a bright day, a moonlight night OR a scary horror set. A couple of useful web sites on lighting: [http://accad.osu.edu/~fkalal/752_sp07/project1.html](http://accad.osu.edu/~fkalal/752_sp07/project1.html) [http://www.cambridgeincolour.com/tutorials/natural-light-photography.htm](http://www.cambridgeincolour.com/tutorials/natural-light-photography.htm) Some place you might start are: Shadows offer clues to the nature of the light source. For example, if a row of windows is shadowed and the shadows are hard edged and parallel, the source is direct sunlight. If the shadows are fairly distinct but are skewed, the source is an artificial light fairly close by. If the shadows are soft and diffuse , the source either is very broad or consists wholly of reflected light. If you are lighting a scene that has a particular time of day or specific interior location, make sure your shadows match accordingly.  Color can also give clues to the nature of a light source. Natural sunlight has a blue cast when seen during the day. This is due to shorter wavelengths of light being more efficiently scattered by atmospheric molecules than longer wavelengths. As such, the human eye responds to these shorter wavelengths and the brain interprets the color as blue. In contrast, sunsets and sunrises appear more reddish because longer wavelengths have survived the trip through the atmosphere while the shorter wavelengths have been scattered away. As for artificial light sources, incandescent bulbs (soon going the way of the dinosaur) produce reddish or yellowish light. Other bulbs, such as fluorescent and tungsten, may have green or blue casts. Because of the switch to fluorescent bulbs manufacturers have been making “natural” light bulbs, bulbs that imitate the light from an incandescent bulb. On a more technical level, light color is indicated by specific color temperatures measured in kelvins. If you are lighting a scene that has specific light sources, such as a wall sconce, skylights, or even candles, make sure your light colors are correct. Continue researching color and light information, inspiration, and imagery. One way to practice naturalistic lighting is to reverse-engineer photographs. That is select a photo and try to determine what the light sources are at the time the photograph was taken. This sunlit scene for example.  Based on the shadow of the girl’s chin on her neck and the slight rim on her right shoulder, it’s apparent that sunlight is arriving from the screen left and from behind. The light is not strong, however. This could be due to an overcast day or the fact that nearby buildings are reducing the total amount of sunlight. Shadows on the screen right wall and window also indicate that bushes or other foliage may be reducing the light. A strong fill arrives from the photographer’s position. Based on the light color and diffuse quality of the shadows, it’s apparent that this light is reflected sunlight. The concrete, the white wall and the etched glass window make excellent reflectors. In fact, the window is contributing a small amount of light to the edge of her left cheek, which fails to become overly dark. If you were recreating this photograph you would actually have to create lights to mimic the contributions of all that reflected light. Exercise Part Two—concerning lights. Something hopefully fairly simple with colored lights. Open partTwo.ma and pretend that this object is sitting on a window sill. Light coming from the left is coming from a window and it is a cloudy but bright day. Light coming from the right is coming from an incandescent bulb in a table lamp. The intensity of both of these lights are about equal. You can give a light a _**negative**_ intensity so that it **_removes_** light from a scene. The slider won’t let you do this you must type in the value into the Intensity field. You can tell lights to cast or not cast shadows—you have to set this one light at a time.  Or you can say that an object can or cannot receive a shadow. In the Attribute Editor, under the Shape Node, click on Render Stats. In here, you can uncheck “Casts” and “Receive” Shadows. You can exclude individual objects from a light’s illumination using Light Linking. This is an advanced technique that is not typically needed until Arts235, but if you want to see it let me know. --- Learn more… - <https://docs.arnoldrenderer.com/display/A5AFMUG/Ray+Depth> - <https://academyofanimatedart.com/maya-lighting-and-rendering-tricks/> --- tags: #3d #maya #lighting #resources home: [[! 3d modeling- maya]]