Introduction
Lighting in 3D animation is generally performed by the tools available in various software packs. In distinction with 2D animation where every frame should be painstakingly painted and filled in with the required tints, lights, and shadows, lighting in 3D animation is performed by pointing the source of light, while the software provides all the necessary computations of the light and shadow positions, tints and coloring of the lit objects. The aim of this paper is to provide the literature survey associated with lighting techniques and means in 3D animation, as the actual value of using the proper software is explained by the correct computations that will require too much time if performed manually.
Lighting Principles
In general, lighting is regarded as the most difficult aspect of 3D modeling and animation. In general, it requires a detailed study and is of particular concern for those who are deeply involved in modeling and animation. Basically, the realistic representation of the lighting scene in 3D modeling presupposes sufficient knowledge of light physics. The light in any scene involves at least two main components: the source of light and the ambient light, which should be put in a scene in accordance with the particular rules. Hence, as it is stated by Boughen (2008, p. 345):
There is some considerable variation in the control over these lights, but this is not quite enough for realistic effects. A scene using standard lighting techniques simply looks rendered. Those images that are the most realistic use advanced techniques such as ray tracing and radiosity. In ray tracing, each ray of light is followed back from the viewpoint to its origin, in order to determine its color and intensity.
Hence, for instance, looking at any object we see the color of the object and its structure. The lighting is seen depending on the angle of light source position, and the dispersion of light. Hence, the light falling on any object may consist of direct light, ambient light, and tint which is originated from reflected light from other objects. Additionally, the light color may be tinted by the objects that were net by the light on its way to the object that we observe: glass, water, curtains, clouds, atmosphere, etc.
The aspect of the color intensity depends on numerous factors, as the intensity of direct light differs essentially from the reflected and dispersed light. Hence, the process of tracing the light in 3D modeling and animation requires considering all these factors. Transparent and reflective features of every material or object included in the scene should be taken into consideration for a better reality of the picture.
Lighting Physics Overview
As for the matters of the traditional representation of all the physical processes associated with light tracing, numerous aspects should be combined, especially if numerous light sources and surfaces are required to be included. The light interference and diffraction rules need to be considered. Hence, as it is stated in Nikodym (2010), the position of the sources is the basis of creating the light image of the scene, however, another important aspect is the position of the camera, and “shooting” angle:
Radiosity also uses basic physics to combine together the effects of multiple light sources and surfaces. The results are added to the scene itself, rather like a general bitmap that is applied all over. Shadows and lights are handled well by this method, but it is only really suitable for diffuse surfaces, and not reflective surfaces – if the camera moves, the reflection will change, and so you will need to use a reflection map in such instances. (Nikodym, 2010, p. 119)
That is why manual light modeling is not regarded as the best solution for 3D animation, and various software tools are used. Animator “tells” the program where the light is located (where it comes from), and the shadows, lights, tints, reflections, etc., are made by the program. Software tools are also featured with particular patterns of light reflection and transparency, hence, the type of material should be stipulated, and the program makes all the necessary computations.
Contemporary 3D modeling and animation are based on numerous techniques and tools for creating the realistic lighting of a scene. In general, the three-dimensional platforms for creating the textures and lighting patterns are based on the computation of the location of the graphic element as well as their features (i.e. how these elements will reflect or disperse light).
Lighting Classification
Each source of light may be regarded from at least four various components:
- Intensity
- Direction
- Color
- Size
In general, these aspects are self-explanatory, though these components define the quality of light, which is one of the key components for 3D modeling. While the origin of light is not the key element of the modeling process, there is no necessity to review the variety of sources in accordance with the light intensity. However, dynamic rendering of 3D animation requires the observation of key compositional rules which are used by painters and photographers.
Hence, as it is stated in Lasseter (2008), the low angled lights are perfect for side lighting, which helps to highlight the most important features of the object and give a clear representation of the shape and texture of the object. The high-angled light gives the flat perception of the image, that is why it is rarely used by artists. Backlighting is similar to low-angled light. Hence, if the silhouette is needed, backlighting is the best solution.
Light intensity helps to emphasize the required details. Similarly to photograph, overexposure, as well as underexposure causes the loss of details on the image, that is why, the light intensity is selected in accordance with the aims of the scene. If the scene is dynamic, the light intensity may be high, while the calm scenes require mild light and low light intensity.
The light color is suited in accordance with the traditional aspects of color perception. It defines the natural look of an image, as the color of the light gives a specific tint to an object, hence, the entire scene may look natural or unnatural. For instance, people got used to see cheese yellow, and if it is lit with green light, the human perception will be tricked, and few would believe this cheese is not spoilt. (Kerlow, 2009)
Size of the light source generally defines the sharpness of the shadows, as smaller sources originate shadows with sharper edges, as well as help to see the structure of an object.
Conclusion
Finally, it should be stated that lighting rules in 3D modeling are similar to lighting rules in photography and painting, as the composition rules are based on the human perception patterns, and depend on the physics of light, its geometry and nature.
References
Boughen, N. 2008. LightWave 3D 7.5 lighting. Wordware Publishing, Inc.
Kerlow, I. 2009. The Art of 3D Computer Animation and Effects. John Wiley & Sons; 4th Ed.
Lasseter J. 2008. Principles of Traditional Animation Applied to 3D Computer Animation, Computer Graphics, pp. 35-44, 21:4.
Nikodym T. 2010. Ray Tracing Algorithm For Interactive Applications. Czech Technical University, FEE.