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Pixel and Vertex Shading (Page 6/9)

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

Vertex Programming Features / Benefits

Below are some of the features of a programmable vertex shader:

- Complete control of transform and lighting hardware
- Complex vertex operations are accelerated in hardware
- Per-vertex set up for per-pixel bump mapping
- Character morphing and shadow volume projection
- Custom vertex lighting
- Custom skinning and blending
- Custom texture coordinate generation
- Custom texture matrix operations
- Custom cartoon-style lighting
- Custom vertex computations of the programmer’s choice
- Offloads vertex computations freeing up the main CPU -- making more physics and simulations possible

Basically, vertex programming allows a programmer to create advanced and sophisticated effects in real time, in hardware and not be limited to a set of predefined functions either.

The Vertex Programming Process
The process goes something like this: You have 3 vertices that form your typical triangle polygon. These vertices are fed into the vertex manipulator. When inside, each vertex can be changed, manipulated and controlled in any manner. Any number of changes can occur while inside the VM. The programmer can choose from his imagination. It’s the sky’s the limit basically. Once the vertices are outputted, they could have been changed coordinately. Their colors could have changed, transparency changed, or locations. What’s really cool about this process though is that the programmer can choose which vertex he wants changed. It can be all or just one, or even none. He can decide that only vertex 1 and 2 needs to be changed, then outputted. The next three vertices that arrive, he can choose to do something different again or nothing at all. Also, every vertex can be changed in the same manner should that be what the programmer chooses.

Changing all these properties will give you limitless special effects for objects. Effects can be applied entirely to an object or just to certain sections of it for subtle details. The possibilities are “nfinite” and limitless.