Using 2D in a 3D World
With the proliferation of computer graphics technology in professional practice, there is a great deal of confusion surrounding how to effectively and efficiently use "2D" or "3D" in renderings and other visual presentations.
The question we hear most often is, "Are your image libraries 2D or 3D?" Professionals and artists alike feel a push to generate three-dimensional computer renderings to provide state-of-the-art presentations to their clients and remain competitive with their peers. Naturally, when attempting to represent the three-dimensional world we live in, one would assume that one needs to develop renderings using three-dimensional objects. This, as we shall learn, is not true at all.
3D Expressed via 2D
For centuries, we have communicated three-dimensional concepts via a two-dimensional, flat media -- paper. These renderings employ the principles of perspective: foreshortening, diminution of size, overlapping objects and converging lines. These principles have been well known since the Renaissance. Even computer graphics that are developed using true three-dimensional objects are eventually reduced to a two-dimensional view, either to the computer's monitor or to film, prints, etc.
Even in the world of virtual reality, where the sense of a three-dimensional environment is maintained, you find the entire experience built upon 2D images. The reason why 2D imagery is used becomes obvious: a) a far greater sense of realism, b) simplicity in development, and c) rendering speed. This first point is perhaps the most important. The entire purpose of a rendering or simulation depicting the real world is that it should be an accurate portrayal of the real world.
Man-made vs. Nature-made
Any real world graphic can be reduced to two aspects, each complimenting and working off each other. These two aspects are, in fact, the essence of architecture. They are: man-made geometric objects and nature-made organic objects. Examples of man-made objects are planes, cones, spheres, columns, etc. Looking at any built environment, one can readily see these shapes repeated over and over again. One thing also becomes clear, all of these objects have a "surface". While it is true that these objects have depth, people don't experience this cross-section. Only the surface characteristics are of any real importance. To accurately represent these surfaces, 2D surface maps are used. They are called "texture maps", or sometimes "bitmaps", and are usually developed to repeat themselves seamlessly over a surface. Most rendering software is built upon the notion of geometric space. Yet, a problem arises when we try to extend this concept of man-made geometric objects into the realm of nature-made organic objects.
People and plants are the nature-made organic objects that bring life to your renderings and virtual worlds. Capturing this essence of life eludes mathematicians, no matter how complex their geometries or fractal algorithms. It is entirely for this reason that organic objects that populate a scene should be developed from the real world: capturing the life essence. Not doing so creates a cold, lifeless, foreign and alien-like world, which certainly is not the goal of any architect or artist trying to sell the client on a project proposal!
Speed and Simplicity
The other reasons for the efficient use of 2D organic objects is rendering speed and simplicity in development. 3D, VRML or virtual reality models are built entirely from simple 3D objects that have a 2D "surface" texture map applied to them. The 2D organic objects can be placed in simple rectangular polygons. As will be demonstrated below, the area surrounding these objects is made transparent so that the geometric border surrounding the 2D object disappears, leaving only the object as it would appear naturally.
This technique works equally well for static renderings or dynamic walk-through's. A "static" rendering is one where, while the computer model was developed as a three-dimensional construction, the rendered image is displayed from one set viewpoint. This viewpoint is what we convey when discussing an architectural or artists rendering and is used in at least 80% to 95% of all real-world presentations. Often, these renderings are set up with light sources to enhance the realism through the casting of shadows. It is here that 2D photorealistic objects really outshine their 3D counterparts: for simplicity, speed and life-like realism!
How to Do It
For each organic object, a tree for example, simply place a proportionately sized polygon in the scene perpendicular to the "camera" viewpoint. Assign the appropriate 2D image file to the polygon as a "map" or "decal". In order to assure the proper shadow angles, it may be necessary to first "flip" this image left to right and save it with a new file name. This is easily done using any paint or image processing software. If lighting is being used and you want to cast a realistic shadow, add a second polygon of similar size, bisecting the first one. Set the second polygon perpendicular to the light source, then map the same image file to this polygon.
When rendering in this manner, you have reduced your "face count" from the potentially thousands it would take to simulate a tree geometrically (a fake looking one at that) to only two faces. The result is a real looking scene that retains the life-like essence so necessary for real world simulation. Repeat this same procedure for people, etc.
Dynamic 3D, VRML or virtual reality walk-through's operate in much the same manner as above. By "linking" the polygons to the camera and light source, as you move from point to point, the object always appears to be facing you and doesn't become flat. Similarly, with a moving light source over time (like the sun), linking the object will maintain a realistic shadow pattern. If the animation portion of your rendering software is unable to link and pivot objects in this fashion, another technique works equally well.
Place two or three bisecting polygons at 60 or 90 degree angles to one another and map each with the same image. In this way, when moving around the object, it never appears flat, as the next image fills in for the last, always giving the appearance of a full object. The perceptual realism to the eye and the users mind is maintained, overcoming any criticism by those claiming the image isn't truly three-dimensional.
Using 2D seamless texture maps and real world imagery, specifically developed for enhancing 3D computer models in the manner outlined above, is superior to any mathematically generated or geometrically created object. The advantage of simplicity of model development, rendering speed and most importantly life-like essence and realism, demonstrates some of the many benefits gained with using 2D imagery in a 3D world
© 2009 Realworld Imagery Inc.
