koobas.hobune.stream
Simple Rotation
Hey guys,
I'm new to unity and i'm already stuck on what seems to me as the simplest of functionality. I can't get the hang of rotations..
Let's say i have a Vector3(0,5,0) and i want to rotate it 30 degrees over the x-axis and 55 degrees over the y-axis, with pivot point Vector3(0,0,0).
How would one go about to achieve this? I have been wrestling with Quaternions and Transforms, but to no avail..
Any help is most welcome!
There are several ways. Quaternions, though more complicated if you dig into their math, present the simpler alternative in terms of lines of code.
With quaternions, you can instantiate a Quaternion object using one of the static methods in the Quaternion class. You mention rotations about specific axes, so we can use the AngleAxis method to create a suitable quaternion. These are then multiplied onto the vector you wish to rotate. The result is the rotated vector. So the example you described above would be:
Vector3 toBeRotated = new Vector3(0, 5, 0); Quaternion rotateVectorAboutX = Quaternion.AngleAxis(30, new Vector3(1, 0, 0)); Quaternion rotateVectorAboutY = Quaternion.AngleAxis(55, new Vector3(0, 1, 0));
Vector3 afterRotation = rotateVectorAboutX * rotateVectorAboutY * toBeRotated;
Note that the order must always be Quaternion*Vector, never Vector*Quaternion. I'm not a math wizard, but my guess is that this is related to the dimensionality of their underlying matrix representations. When you multiply matrices, the "connecting" dimensions must match, i.e. [1x4][4x4] is okay, but not [4x1][4x4].
There are plenty other ways to go about this, like EulerAngles, if you're more into that.
Thank you very much! I've been trying to get this to work for a week, searching the forums like crazy. But this is very clear example!
wow, I never knew you could multiply Quaternions by Vectors, I guess this is some of the underlying reasoning behind Quaternions being called Euler parameters?
[edit:] and infinite respect btw to this answer.
