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anders211

coordinates transformation

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Assuming you're trying to calculate a reflection vector:

 

Vreflection = V - 2 * (n dot V) * n

 

for any n.

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In case that you really want to do more than calculating the reflection vector, and only translation and rotation but not scaling plays a role:

 

All your vectors are given in a space described by the identity matrix, i.e. with

   o = [ 0 0 0 1 ]t

   x = [ 1 0 0 0 ]t

   y = [ 0 1 0 0 ]t

   z = [ 0 0 1 0 ]t

 

The other space is described by

   o', x', y', z'

 

What you want is a transform M that maps the original space onto the given one:

   o' = M * o

   x' = M * x

   y' = M * y

   z' = M * z

 

Because each of oxyz has a single 1 and otherwise 0s as elements, and the 1 is stored at different rows, each of those mappings above just pick a single column from M:

   M * x = M * [ 1 0 0 0 ]t = M1st column

   M * y = M * [ 0 1 0 0 ]t = M2nd column

   M * z = M * [ 0 0 1 0 ]t = M3rd column

   M * o = M * [ 0 0 0 1 ]t = M4th column

 

In other words, the transform M is the matrix

   M := [ xyzo' ]

 

If you want to transform a vector v from the original into the mapped space, you have to apply

   v' = M * v

If you want to transform a vector v' from the mapped into the original space, you have to apply

   v = M-1 * v'

Edited by haegarr

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