Alpha (Material stage keyword)

Description

The alpha keyword multiples the alpha channel of the associated map by the given value. Use of this keyword only makes sense with blend modes that respond to alpha, such as the blend blend mode.

Usage

alpha <alphaval>

Parameters

• alphaval - the value by which the alpha channel of the image map should be multiplied

Example

The following stage blends an image with an alpha value of half its original alpha channel

{
   blend blend
   map path/to/image.tga
   alpha 0.5
}

Notes

An image with no transparency has an alpha channel of constant 1.0, therefore this keyword can be used even for images which contain no explicit alpha.

Photoshop 7 does not save transparency information into an alpha channel when dealing with targa images. You must download the updated Targa export plugin from Adobe . All other versions of Photoshop work correctly.

This keyword is particularly useful for controlling the strength of a mirrorRenderMap or cubeMap stage.