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Ask HN: How does choice of coordinate system affect 3D transformation?
2 shivajikobardan 2 8/26/2025, 7:30:35 AM
I am going through rotation about an arbitrary axis in three dimensions, rotation about x, y and z-axes in three dimensions etc.
And there are coordinate system that are called as:
- left handed coordinate system
- right handed coordinate system
For some reasons I have observed ambiguousness in various rotation matrices.
Example: Rotation about y-axis by t could be written as:
$$
\begin{bmatrix}
cost & 0 & -sint & 0 \\
0 & 1 & 0 & 0 \\
sint & 0 & cost & 0 \\
0 & 0 & 0 & 1
\end{bmatrix}
$$
I have seen someone interchanging the sin of sint in some textbooks/authors/videos(like this: https://www.youtube.com/watch?v=ZEXpxIwpGbY)Check 25:28 of the video and step numbered (3).
This is frying my brain since few days. I know getting free assistance in this huge topic is not possible. But even if you could display a small support, small guidance, that would be greatly push me through this phase.
References:
https://stackoverflow.com/questions/19747082/how-does-coordinate-system-handedness-relate-to-rotation-direction-and-vertices
https://www.cairographics.org/cookbook/matrix_conventions/
The reason behind this is called pre-multiplication vs post-multiplication technique of matrix transformation.
Post-multiplication
- transformation matrix appears after the position vector matrix
- position vector matrix in homogenous coordinates is represented as a row matrix.
Pre-multiplication
- transformation matrix appears before the position vector matrix
- here the position vectors in homogenous coordinates are represented in column matrix.
Textbook reference: Mathematical elements for computer graphics Rogers/Adams
https://www.math.umd.edu/~wmg/Marsh.pdf