Thursday, March 23, 2000

"Transform and Lighting"

Now, I'd like to write a few words on the "Transform and Lighting" function that is supported by the GeForce 256 GPU. This function radically transforms the appearance of objects, and their nearby environment, by adding a level of photorealism that truly brings affected objects to life. Thanks to the GPU's ability to calculate lighting effects, the objects take on a totally new dimension, and achieve new levels of realism. Light, and shadows become living things, and truly begin to affect one another in a realistic manner.

In fact, "Transform and Lighting" is really two separate mathematical processes that until now were processed by the computers CPU; thus - potentially - greatly upsetting overall system performance. With the GPU taking over the load of the tasks of adding increased realism to 3D scenes, the CPU is free to use its processing power to calculate the physics of the virtual environment, and provide more time to artificial intelligence calculations.

The "transform" function serves to define 3D objects. It dictates how many 3D objects can be placed within a scene, and how sophisticated a 3D environment can be. In particular, this function is used to render the curves of an element, in a series of segments. The more segments there are that constitute the curve, the more strenuous the calculations are that need to be performed. Thus, since there are some scenes in which we can expect to find - literally - thousands of curves, offloading the necessary calculations from the CPU, to the GPU will ease the former's load considerably.

The "Lighting" effect is a horse of a different color. The human eye has more ability to sense changes in contrast than in colors, meaning that lighting takes a prime role in how we perceive things in the world. In other words, an image with lighting affects provides more information for the viewer. Lighting is presented in two main categories: diffuse lighting, and spectacular lighting. Diffuse lighting assumes that the light is falling evenly on all areas of a surface, and as such, the perception of the light's brilliance would not be affected by the viewer's position relative to that surface. Spectacular lighting is different in the sense that the brilliance of the light depends on the position of the observer, relative to the light source itself. In short, spectacular lighting changes with the object, and thus can't be calculated ahead of time. You can then understand that only a GPU with a dedicated circuit for calculating lighting effects can stand up to the heavy load of calculations that must be performed every moment. While programmers can use texture mapping to create spectacular lighting effects, it would be necessary to recalculate the entire environment the moment the observer changes its position in scene; a very demanding state of affairs. All said, spectacular lighting is particularly useful in 3D for displacement within scenes, and to create different textures on an object's surface.

To take advantage of the integration of the "Transform and Lighting" engine, it is essential for a game to use DirectX 7, or an OpenGL API. As you might expect, the game can't be using its own emulator to render T&L effects, or else it can't take advantage of the GeForce 256 integrated "Transform and Lighting" functions. Quake 3 is actually a prime example of a game that the GeForce 256 permits to be rendered with a superior level of definition, without sacrificing any loss in performance.

Next: Cube Environment Mapping.