3D Graphics

A video card teams up with a system's motherboard/chipset, CPU, memory, and PCI or AGP interface, to put 3D graphics onto the computer screen. The first stage of the process used to be called Geometry, but now it's commonly referred to as Transform and Lighting or T&L. The geometry used to be done completely by the CPU, but now some chipsets such as ATI's Radeon, and Nvidia's GeForce2 and GeForce3 families have transform and lighting engines enabling them to perform much of that work themselves. A video card with a T&L engine, or similar technology, will be a much better 3D performer than a card without.

·  Stage 1: Transform and Lighting

When a program instructs the computer to put a 3D image on the screen, the computer starts with the first frame and calculates where the vertices and lines should be. These configurations of vertices and lines are called polygons (or triangles). Currently, a medium range 3D card has a throughput of 20 million triangles/sec. The higher the triangle count, the smoother the images will appear on your screen.

The next step is lighting. Shading, reflection, shadows, and other lighting effects are added to the scene depending on an object's position relative to the light source.

In addition, when a character moves in a 3D game, the T&L engine is also responsible for recalculating the position of all the objects in the image.

·  Stage 2: Rendering

The graphics card is in charge of the rendering stage. During the rendering stage, the "wire-frame" image created during T&L is filled in with color and texture.

A number of different techniques may be used during the rendering stage. The more techniques used, the more realistic the image appears. But the down side is that it's more work for your card and CPU, and could affect performance. When the system can't keep up it may cause the frame rate to decrease. The frame rate is the number of frames that can be displayed in a certain amount of time. An excellent 3D card can display 60 frames/sec. even at high resolutions (6/01).

If the frame rate gets too low, then movement will appear choppy--a problem referred to as dropped frames. Some video card makers deliberately pick and choose which 3D techniques to include, in an effort to steer clear of dropped frames.

Here is a list of 3D techniques you are likely to see mentioned.

• Gourad Shading: Helps define the shape of 3D objects, giving them the appearance of depth.
• Clipping: Determines which parts of objects will not be visible on the display so that the processor doesn't waste time with things that the user won't even see.
• Transparency: Makes things look transparent.
• Texture Mapping: Creates textures such as wood, plaster, or stone.
• Dithering: Tricks the eye into seeing more colors than are actually present. Fewer colors mean fewer computations.
• Fogging: Fogging blurs objects that are in the distance so they look more realistic. In addition, blurred objects are quicker to compute because they are less detailed.
• Filtering: Filters, such as the "bi-linear" filter are used to clean up and smooth out images that otherwise might look blocky.
• Anti-aliasing: A technique used to reduce the noise (speckling) present in an image.
• Bump Mapping: Makes surfaces look bumpy.
• Z-buffering: Calculates the pixels that will be loaded into the frame buffer.
• Alpha Blending: Blends two bitmaps together making one appear transparent.
• Interpolation: Smoothes out the image, making it look realistic even up close.
• MIP Mapping: Stores several versions of a textured bitmap to prepare for instances when the user moves close to an object. Without MIP Mapping an object will blink and sparkle as the processor continually recalculates the image. With MIP Mapping the texture of the object will get larger making the user feel as though they are getting closer.
• Perspective Correct: This makes a textured 3D image look realistic from any angle.
• Texture Mapping: This puts a bitmap onto a 3D surface to make the object look more realistic.