A 3D Primer
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What Are 3D Graphics?

Simply put it is the field of computer graphics concerned with generating and displaying three-dimensional objects in a two-dimensional space (e.g., the monitor screen). Whereas pixels in a 2-dimensional graphic have the properties of position, color, and brightness, a 3-D pixels adds a depth property that indicates where the point lies on an imaginary Z-axis. When many 3-D pixels are combined, each with its own depth value, the result is a three-dimensional surface, called a texture. In addition to textures, 3-D graphics also supports multiple objects interacting with one another. For example, a solid object may partially hide an object behind it. Finally, sophisticated 3-D graphics use techniques such as ray tracing to apply realistic shadows to an image.

Converting information about 3-D objects into a bit map that can be displayed is known as rendering, and requires considerable memory and processing power. In the past, the ability produce and manipulate 3-D graphics was available only on powerful high end workstations, but now 3-D graphics accelerators are commonly found in newer PCs. The graphics accelerator contains memory and a specialized microprocessor to handle many of the 3-D rendering operations.

Z Buffering

An algorithm or mathematical process used in 3-D graphics to determine which objects, or parts of objects, are visible and which are hidden behind other objects. With Z-buffering, the graphics processor stores the Z-axis value of each pixel in a special area of memory called the Z-buffer . Different objects can have the same x- and y-coordinate values, but with different z-coordinate values. The object with the lowest z-coordinate value is in front of the other objects, and therefore that's the one that's displayed.

An alternate algorithm for hiding objects behind other objects is called Z-sorting. The Z-sorting algorithm simply displays all objects serially, starting with those objects furthest back (with the largest Z-axis values). The Z-sorting algorithm does not require a Z-buffer, but it is slow and does not render intersecting objects correctly.

3D Modeling

In 3D graphics, the digital representation of the surface of an object. In addition to two-dimensional qualities, such as color and brightness, a texture is also encoded with three-dimensional properties, such as how transparent and reflective the object is. Once a texture has been defined, it can be wrapped around any 3-dimensional object. This is called texture mapping.
Generally, the process of representing a real-world object or phenomenon as a set of mathematical equations. More specifically, the term is often used to describe the process of representing 3-dimensional objects in a computer. All 3-D applications, including CAD/CAM and animation software, perform modeling.
In computer graphics, an advanced technique for adding realism to an image by including variations in shade, color intensity, and shadows that would be produced by having one or more light sources.

Textures

Well-defined textures are very important for rendering realistic 3-D images. However, they also require a lot of memory, because of this in the past they weren't used frequently. But, with today's faster processors and video card with greater amounts of onboard memory, have become more and more prevalent.  Especially in the development of computer games.  This is also one of the major reasons for the development of the new internal graphics interface, AGP, which allows texture to be stored in and retrieved from main memory. AGP also speeds up the transfer of these large textures between memory, the CPU and the video adapter.

Ray Tracing

Ray tracing requires enormous computational resources, and is supported by only the most advanced graphics systems.  Ray tracing software works by simulating the path of a single light ray as it would be absorbed or reflected by various objects in the image. To work properly, the artist must specify parameters of the light source (intensity, color, etc.) as well as all the objects (how reflective or absorbent the materials are).

The Graphics Accelerator