Chapter 1 An Introduction to 3D Computer Graphics
From ShadeCamp
Although your computer monitor may be a flat two-dimensional surface, objects can be represented in three dimensions using several techniques. Computer software that uses this technology is called 3D computer graphics software. Shade is one of those “3D CG” software applications. If you have much previous experience with 3D graphics, you may want to skip ahead to the next chapter. What follows assumes no experience with 3D.
Contents |
32,000 Years of Art
From the Aurignacian age caves of ancient Europe to your computer, representing the world through art is an ongoing, iterative process of humanity – one you are about to embark on with Shade. Those early cave dwellers represented the world with simple strokes of color. But those cave dwellers knew they were representing their ideas on a 2D model; they had to compensate for the flat medium of a dry cave surface. Some of their descendants compensated for this by using natural materials to make sculpture. Others learned to deepen or lighten color, account for perspective, shadows and reflective surfaces in order to simulate objects within what is known as a Cartesian coordinate system: a system of width (X), height (Y) and depth (Z) that originates at a central point – the origin.
From 2D to a 3D Workspace
When you create art in 3D workspace on a computer, instead of compensating for shapes, reflectivity and lights with strokes of color from a brush, you are recreating the natural universe by placing objects within a simulated space. That simulated space, universe or workspace is measured in global coordinates, with the exact center being the point of origin, and all directions radiating out from that point of origin along X, Y and Z axis. In 3D art, the universe has a center. Even though these coordinates should be called universal coordinates, in the world of 3D art they are referred to as global coordinates.
Consider for a moment that you stand on planet Earth, facing a morning sun and are holding an orange in your hand. You, the orange and the Earth are all influenced in varying degrees by the sunlight originating from its origin – the Sun.
With your computer and Shade, you can do many things that are impossible in the real universe – you can ignore the universe to accomplish specific results. You can work on individual objects, and treat each object as its own center of its own universe. This is known as working in local coordinates - the center of an object in your scene becomes its own origin.
Now imagine making a 3D representation of you on that morning on planet Earth. You can ignore the universe in modeling the Earth, yourself or the orange. You can, for example, develop a skin for the orange based on the center of the orange as its origin, rather than a distance from the center of the solar system. You can develop a mist of particles that originate from your mouth, based on the location of your mouth, rather than the distance from the center of the universe. That’s what it means to work in local coordinates.
In either local or global coordinates, you are working in three directional axis: X, Y and Z., even though the origins are different. Moving forward in your understanding of 3D art, an understanding of the difference between how the real world works and the 3D universe of Shade will empower you as a 3D artist.
What are 3D Computer Graphics?
2D graphics are flat images such as a painting on a canvas or a piece of paper. Remember 3D graphics have a width, height and depth (along the X, Y and Z axes) and can be moved, rotated and manipulated in three dimensional space like real objects can be manipulated in real life.
2D software also differs from 3D software.
Let’s take a look at an image created in 2D and one created in 3D:
2D image
3D image
The second image looks like it has real depth, an effect made possible through the use of 3D computer software simulating how a 3D universe works.
General Workflow in 3D Computer Software
Let’s take a look at the general steps usually followed when creating a scene using 3D computer software such as Shade:
1. Modeling (Building Objects)
The first step in creating a scene is to design and build the objects (such as people, animals, buildings, trees and almost anything else) you want to have in the scene. The concept is the same as building plastic models. You start by building smaller pieces, and eventually assemble the finished model by putting all the individual parts together.
Generally speaking, you can work like a 2D artist and begin with large, vaguely defined shapes, and then work your way towards detailed objects. Unlike a 2D artist, you can jump right to the details if you want.
2. Texturing
Once your models are built, the next step is to apply the appropriate colors, textures, patterns and transparency to each object. These are all the things that are visible to the eye, provided that there is enough light available to see them.
3. Lighting
Not only are studio lighting effects possible in 3D computer graphics, but natural lighting from the sun or sky can be simulated as well. You can set up one or multiple light sources, adjust the brightness or luminosity of each light, change the amount of ambient or indirect light in the scene and much more.
4. Camera Positioning
Choosing the camera angle is important in communicating the feeling and impression you wish to express to your audience. Placing the camera at an angle to the ground, or having the camera look from within an enclosed space to a wide open space can convey very different things.
5. Rendering
Rendering is the process of transforming the work you did in all the steps up to this point into a picture or animation. Shade calculates rays of light in a scene and how they affect objects within a scene, and that information is likewise affected by the constraints you place on the camera.
In Shade, objects can also be animated. If you wish to create an animation you will need to setup joints along which the objects can move and then edit the animation along a timeline.
The final step will still be rendering, but the result will be a movie instead of a still image.
Characteristics of Shade
The Structure of Curved Surfaces
Shade makes strong use of Bezier curves for modeling objects. These “curved surfaces” are formed of one or more sectional lines running in the horizontal and vertical directions. By editing the shape of these lines, either individually or in groups, we can create the shape of a complex, yet smooth, surface.
The above object is composed of a series of elliptical lines running longitudinally from the fish’s head to its tail, and a series of laterial lines running along its sides, dorsal and ventral surfaces. Surfaces are drawn across the points where the lateral and longitudinal lines intersect. Imagine an umbrella or paper lantern. The flexible material is stretched over the underlying skeleton to form a shape in a similar way that curved surfaces in Shade work. |
