I’ve been experiencing with rotation in blueprint a lot lately, but can’t seem to get the basics straight and I’m finding different, contradictory explainations on the internet, so I’m just gonna ask a few things here:
When do I use which rotation (setworldrotation, setrelativelocation, addlocalrotation)?
Which boundaries do pitch, yaw and roll have? I found some info saying, that they must be between 0 and 360° which kind of makes sense to me, but If I print the rotations to the screen while my programm runs, the rotation values are often negative. So whats up with that?
Imagine I have a blueprint scene “root” and in a relative distance (e.g. 10,0,0) I have a static mesh body (e.g. a cube). If I rotate the root, the static mesh follows accordingly and it rotates around the same axis, which are the axis of the root, right? Shouldn’t be the pitch, yaw and roll compnents of the root and the static mesh be the same than? Because if I try this, I get different rotation values for the scene root and the static mesh body.
If I combine two rotators with the combine module (e.g. both have the values 5,5,5), why isn’t the result the sum (5+5 = 10) but some diffrent value?
I know these questions might be easy peasy for most of you, but I kind of got lost and I can’t seem to find out those basics. So thanks for every help in advance!
Rotators are certainly one of the more confusing things in Unreal Engine. In the real world they are called Eulers (pronounced “Oiler”).
One thing that you must understand is the difference between World space and Local (aka Relative) space. World space is the space that something is in in your world when it has no parental transformation. In world space, +Z is up, -Z is down, etc. Now, local space is the space of something relative to transformations higher up in the hierarchy. In question 3, the “root” is in world space. The cube is subjected to the transformation of the root. Now, the pitch, yaw, and roll components weren’t the same for you. That’s because the root was in world space, while the cube’s rotation was displayed in relative space. The cube is getting the transform of the root by default, and then contributing its own transform on top of that. You can actually change the displayed type of rotation in the Details panel:
So, if your cube’s relative rotation is (0, 0, 0), then it will have the same rotation as the root. And, if you change the type in the Details panel to “World”, then it will be the same as the root.
It depends on the situation. SetWorldRotation sets the rotation of the component in world space, overriding the current rotation or parent’s rotation. So, if you rotate your “root”, and then call SetWorldRotation with (0, 0, 0) on the cube, then your cube will look completely unrotated. SetRelativeRotation sets the rotation of the component in relative space, relative to the parent. So, if you rotate your “root”, then rotate the cube, then call SetRelativeRotation with (0, 0, 0) on the cube, the cube will have the same rotation as the root.
The boundaries don’t really exist. Technically it’s from 0° to 360°, but you can go below 0° and above 360°. If you go below 0, then the degrees will be 360°+x. So, -90° is 270°, and -180° is 180°. If you go above 360°, then the degrees will be x-360°. So, 450° is 90°, and 540° is 180. If you go even further above, like 1080°, then you repeat the process. 1080° is 0°. Oh, and keep in mind, 0° and 360° are the same thing. All of this is how it will visually appear, but if you are doing animation, they do have special meanings, because 1080° would mean “flip 3 times”. Even though -90° is 270°, in animation, -90° would go a short bit backwards, and 270° would go a bit longer forwards.
I explained this in the beginning.
This is one of the great evils of Rotators… there are equivalent rotations! For instance, (-90, 0, -90) is the same thing as (90, 180, 90).
Wow! It feels like I just wrote an article on rotation! I hope it’s not too confusing, and I hope it helps!
I hate to tell you, but you use the one you need. You’ll discover that you need a different node, depending on what you’re doing. One thing I will say is, to avoid problems with the engine change 180 to -180, you might use AddLocalRotation to avoid that.
Again, the boundaries are -180 to 180 or 0 to 360 depending on how you inspect it. You CAN set to yaw to 30000, for instance, if you want to, but you’ll just get a value back in range. If you really can’t stand not knowing what rotation an object has, then you need to start using quarternions instead.
Combining rotations can be very counterintuitive. They should add up, IF, the object’s location is the same.
Thank you so much for your reply! These answers are really helpful, especially “findlookatroation” and the last part about the different roatations.
P.S. I’ve started three month ago, not in 2018
wow, I couldn’t have hoped for a more thorough explaination, so thank you so much! This was really helpful! Of course I have some follow-up questions
If I set the relative rotation of the cube to 0,0,0 and change the world rotation of it’s root to, let’s say 50,50,50, the relative rotation of the cube remains 0,0,0 and it’s world rotation is equal to the roots (50,50,50), is that correct? Is it somehow possible that the relative rotation of the cube changes (unwantedly) during the run of the programm without me redefining it?
So it doesn’t really matter if I dont use “clamp axis”, Unreal calculates the values on it’s own?
Have you had any experience with a sudden flip of the rotation somewhere around 0° or 180°? I sometimes experience a change in sign (from 180° to -180°). This appears if i work with unreal leap, so maybe that question is to offbeat
this cleared up a lot aswell, especially the first and the last point, thanks for your help! I tried using quaternions in the past but I didn’t get very far because I don’t know how to define them (4 values? whats w?) and I couldn’t figure out how to combine them with Euler-Roation-values (Is it even possible?)
