dot3 bump mapping doubt

Graphics and GPU Programming Programming

Started by LukeSkyRunner February 09, 2003 03:50 AM

1 comment, last by LukeSkyRunner 21 years, 2 months ago

136

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February 09, 2003 03:50 AM

If my light vector and normalmap need to be a "RGB" format for normal direction how can I apply negative values to the normals?

S1CA

1,418

February 09, 2003 09:27 AM

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:

quote:...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.

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Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com

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