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D3D Texture Coordinate Processing?

Started by Void Jul 3, 2000 at 1:15 AM 3 replies 200+ views

Original Post

Jul 3, 2000 at 1:15 AM

Does any understand how the matrix for texture coordinate processing works? Like for animating textures using translation in UV (2D), the matrix is

    
1   0  0  0
0   1  0  0
du dv  1  0 (du and dv change each frame)
0   0  0  1

How does the maths work??..

WitchLord

Jul 3, 2000 at 10:25 AM

The math works exactly (almost) like when transforming 3D coordinates. The only difference is that now you are only using 2D coordinates so that last column and row aren't used.

        
Translation matrix 


tu = tu + a 
tv = tv + b


1 0 0 0
0 1 0 0
a b 1 0
0 0 0 1


Scale matrix


tu = tu * a
tv = tv * b


a 0 0 0
0 b 0 0
0 0 1 0
0 0 0 1


Rotation matrix


tu = cos a * tu - sin a * tv
tv = sin a * tu + cos a * tv


 cos a  sin a    0      0
-sin a  cos a    0      0
   0      0      1      0
   0      0      0      1

- WitchLord

Edited by - WitchLord on July 3, 2000 11:26:22 AM

S1CA

Jan 1, 2002 at 5:24 PM

The API simply ignores the unnecessary parts of the matrix.

When using projected textures, it expands the coordinates internally to u,v,1

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

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