Applying transformation matrix to 3D vertex coordinates

[Robert Kern]

PhilC wrote:
> '''
> ################################################
> Task:-
> to apply a translation array to an array
> of 3D vertex coordinates to produce the
> resulting location of each vertices.
> 
> Translation array and vertex coordinates taken from
> a Truespace COB file.
> 
> The text in the COB file looks like this:-
> 
> Transform
> -2.11786 -0.817596 0.946387 0.864939
> 0.405189 1.25484 2.11894 0.434915
> -1.16679 1.9198 -0.981965 1.13894
> 0 0 0 1
> World Vertices 8
> -0.200000 -0.029486 -0.236313
> 0.200000 0.029486 -0.163687
> -0.200000 0.370514 -0.282911
> -0.200000 0.370514 0.117089
> -0.200000 -0.029486 0.163687
> 0.200000 0.029486 0.236313
> 0.200000 0.429486 -0.210286
> 0.200000 0.429486 0.189714
> 
> ###############################################
> '''
> # script start 
> 
> import Numeric
>  
> transArray = Numeric.array((
> (-2.11786, -0.817596, 0.946387, 0.864939),
> (0.405189, 1.25484, 2.11894, 0.434915),
> (-1.16679, 1.9198, -0.981965, 1.1389),
> (0, 0, 0, 1)
> ))
> 
> # a "1" added to the end of each set of vertix coordinates
> vertArray = Numeric.array((
> (-0.200000, -0.029486, -0.236313, 1),
> (0.200000, 0.029486, -0.163687, 1),
> (-0.200000, 0.370514, -0.282911, 1),
> (-0.200000, 0.370514, 0.117089, 1),
> (-0.200000, -0.029486, 0.163687, 1),
> (0.200000, 0.029486, 0.236313, 1),
> (0.200000, 0.429486, -0.210286, 1),
> (0.200000, 0.429486, 0.189714, 1)
> ))
> 
> print transArray
> print ""
> print vertArray
> print ""
> 
> transArray = Numeric.reshape(transArray,(4,4))
> vertArray = Numeric.reshape(vertArray,(4,8))
> 
> print Numeric.matrixmultiply(transArray,vertArray)
> 
> # script end
> '''
> ##################################################################
> Result:-
> 
> [[ 0.5708016   0.10309048  0.70481144 -1.12413     0.1022124
> 0.03400637  0.63866924 -1.12413   ]
>  [-0.6688108   0.57729922 -0.19537307  4.213884    0.3408408
> 0.72615216  0.66384632  4.213884  ]
>  [ 0.273571    1.26381257 -0.66763452  0.909945   -0.585931
> 1.13709619  0.39979     0.909945  ]
>  [ 0.2         0.429486   -0.210286    1.          0.2
> 0.429486    0.189714    1.        ]]
> 
> Am I going in the right direction?

No. The reshape didn't do what you want it to. The elements will have the same
order; it won't transpose the array. To do that, use the transpose() function.

> What do I do with the result? :)

When you have it correct, the last row will be all 1s. Ignore it.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco