#168648 - Echo49 - Wed May 13, 2009 4:50 am
At gbatek the translation matrix is identified as:
| Code: |
_ Translation Matrix _
| 1.0 0 0 0 |
| 0 1.0 0 0 |
| 0 0 1.0 0 |
|_m[0] m[1] m[2] 1.0 _| |
Shouldn't the translation vector be on the far right of the matrix instead?
#168650 - Dwedit - Wed May 13, 2009 6:39 am
If the coordinate is a column, translation goes on the right
If the coordinate is a row, translation goes on the bottom, and the translation matrix is Right Multiplied with the coordinate instead of Left Multiplied.
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Last edited by Dwedit on Wed May 13, 2009 6:41 am; edited 1 time in total
#168651 - sajiimori - Wed May 13, 2009 6:39 am
@Echo49:
On column-major systems, yes, but not on the DS.
(Do I have that right? As I recall, DirectX is column-major and OpenGL is row-major...?)
#168652 - Cearn - Wed May 13, 2009 9:03 am
| sajiimori wrote: |
| (Do I have that right? As I recall, DirectX is column-major and OpenGL is row-major...?) |
Technically, it's only a notational difference. Most math and OpenGL books will use column-major notation, whereas DirectX uses row-major. In memory, the order of the elements are the same. It's just that C uses row-major as well, so OpenGL matrices don't translate directly to C-matrices.
If the coordinate vectors are columns, the matrix will be column-major, and when the vectors are rows, the matrix is row-major.
| Code: |
A ? X = ( X^T ? A^T )^T
________________ ___ / _______________ \ T
| ux vx wx tx | | x | | _________ | ux uy uz 0 | |
| uy vy wy ty |?| y | = | | x y z 1 |?| vx vy vz 0 | |
| uz vz wz tz | | z | | --------- | wx wy wz 0 | |
| 0 0 0 d | | 1 | | | tx ty tz d | |
---------------- --- \ --------------- /
|
#168655 - Echo49 - Wed May 13, 2009 11:54 am
Ah I see.
I was getting confused wondering how in the world that would help translate the vectors.
Thanks!