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dot3 bump mapping doubt

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The hardware biases the values by -127 (IIRC) inside the dot3 operation to turn them into *signed* values, so 0=-127 255=+127 or similar.

A quote from the SDK documentation for DOTPRODUCT3:

...multitexture operations the above inputs are all shifted down by half (y = x - 0.5) before use to simulate signed data, and the scalar result is automatically clamped to positive values and replicated to all three output channels. Also, note that as a color operation this does not updated the alpha it just updates the rgb components.

Simon O''Connor
Creative Asylum Ltd

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