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Pixel and Vertex Shading (Page 7/9)


Posted: February 25, 2001
Written by: Tuan "Solace" Nguyen

Vertex Programming Benefits

Although there are distinct benefits to vertex programming versus pixel programming, the two technologies aren’t competing technologies. Contrary, the two techniques are designed to complement each other to create ultra realistic and ultra responsive graphics.


"Membrane" - This vertex shader example changes
the color of an object as the surface points
toward or away from the viewer.


Paletted Skinning
Using vertex programming, games can contain characters that move incredibly realistically. Their joints will bend and clothes and armor will crease with each other accordingly. When a character moves its arms, their sleeves will stretch at the elbow and crease at the shoulders. All these effects can now be accomplished in real time.

Besides being able to move characters and objects in a believable manner, we can now have characters that can express emotion. When someone isn’t smiling, certain skin creases may not show. However, when they grin, we see dimples and creases caused by muscle movement underneath. These can now all be done using keyframe animation.


Cartoon style vertex shading is now a possibility

Environmental Mapping and Transforms
Because of vertex programming versatility, it can be applied to virtually any environmental effect that the game requires. You can have low moving fog across a valley or fog elevation in certain areas of a scene. Certain objects can appear or be hidden even in the same fog area because the programmer can program the vertex engine to be selective. Suppose I want only hills or mountains higher than 1000 feet to appear, I can have only those that are higher show up through the clouds and have the other ones stay covered until I come close.

Procedural Geometry Deformations
Using the vertex shader, objects that would otherwise stay still in the game can be brought to life. If you have a flag on a flagpole high up in the sky where it’s window, the wind motions can deform and shape the flag by chaos theory. You can have the flag wave, drop, bend, crease, fly, and swirl in any number of combinations. With dynamic deformations, you can finally really destroy things inside a game. It’s now possible to have realistic damage on objects, or even environments.

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