(2019-11-05, 17:35)Philippe Hurbain Wrote: The great thing is that in this mode, the part that was used as reference has a very simple "identity" matrix, all 0 except on the main diagonal where values are 1. These "1" are actually the scaling of the part in relative x/y/z directions. […] Since the length of the beam is oriented along blue Z axis, we'll need to change that third "1" on matrix diagonal.
Aha—so the important thing to know is that all scaling operations happen in the boxes along that diagonal. X-scaling in the top left box, Y-scaling in the center, and Z-scaling in the bottom right. The other boxes get used for rotations (and other functions like shear which we wouldn't be using), so as long as I'm using the part's local orientation (or the part isn't rotated), I'll only ever need to change one box for scaling along a single axis.
And am I accurately summing up what a matrix is to say that its 3 columns represent the x, y and z coordinates of each point being transformed, while its 3 rows represent movements of those coordinates along the x, y and z axes? And that's why, when we scale along the z axis, we're just taking each z coordinate (third column) and moving it a relative amount along the z axis (third row)? Or something like that…