Alpha Blending

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Alpha blending is used to display an image that has transparent or semi-transparent pixels. In addition to a red, green, and blue color channel, each pixel in an alpha bitmap has a transparency component known as its alpha channel. The alpha channel typically contains as many bits as a color channel. For example, an 8-bit alpha channel can represent 256 levels of transparency, from 0 (meaning the entire pixel is transparent) to 255 (meaning the entire pixel is opaque).

Color can be defined with or without alpha values. Color without alpha is RGB; color with alpha is stored as ARGB. Vertex data, material data, and texture data can be used to give objects transparency. The frame buffer also can be used to generate transparency effects.

The list below shows some special effects that can be created using alpha blending.

• Vertex Alpha
• Material Alpha
• Texture Alpha
• Frame Buffer Alpha
• Render Target Alpha

The following samples demonstrate alpha blending.

• Billboarding
• Clouds, Smoke, and Vapor Trails
• Fire, Flares, and Explosions

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