3D Spotlight has finally updated their 3dfx Voodoo 3 tweak guide for the latest drivers.

Alpha Blending. This setting can be used to enable/disable dither
subtraction on the Destination colour during Alpha-Blending. When dither subtraction is enabled, the dither matrix used to convert 24-bit colour to 16-bit colour is subtracted from the destination colour before applying the alpha-blending algorithm. Setting this to Automatic will allow the application in question to use dither subtraction as necessary. Setting it to Sharper will enable dither subtraction, resulting in a sharper image. Setting it to Smoother will disable dither subtraction, resulting in a smoother image. I'd recommend setting this to Sharper.

NOTE Setting 3D Filter Quality to High & Alpha Blending to Sharper will enable the use of a special post filter which results in effectively 22-bit colour. This will provide optimal image quality with the Voodoo 3.

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