You are the very first to give a clear explanation of why computer graphics tech prefer Quaternions. Thanks. This I finally understand.

This is by far the best explanation for quaternions in 3d graphics I have found! The justification to abandon Euler angles is also straight forward, no useless talk about gimble lock. Thank you!

@have_fun1107

Ай бұрын

did you found anything else?

@drobin9040

27 күн бұрын

@@have_fun1107 What do you mean? Other videos on the topic?

@have_fun1107

26 күн бұрын

@@drobin9040 yes or anything else that may help building intuition?

@drobin9040

25 күн бұрын

Have a look at Freya Holmer’s content, she’s awesome at explaining math with visuals.

you helped me understand what it is in first minute, after I couldn't really grasp it after watching 3blue1brown video of 30min. tyvm

I used quaternions for a car wheel. I could separate the expected roll angle for that frame and the steer angle, Then combine them as a single rotation. I would “zero” the rotation by finding its inverse, make the steering angle change, then roll change, then reapply the inverse of the inverse.

This is great! Very well explained and beautifully visualized

this is very much over my head in understanding but its awesome to hear you talk about quaternions!

'Have a nice day and please don't use Euler angles.' LOL. Awesome. 👍

Well explained!

This was helpful, I appreciate it.

wow, well done!

This might be enough for a first toehold in the subject!

I need more! All others videos are copypaste of the sames videos and "papers", no one teach how to use them. I need it for physics.

5:07 I don't understand how _theta_ and _-theta_ are the same angle ( or _q_ same as _-q_ ). That doesn't make sense. *Edit:* Oh, because V and -V point in the opposite directions. Okay. So rotating in the opposite direction when the axis vector is inverted, actually results in the same rotation. Now I think I get it.

Достойно!

Hello do you know how to use it for finding joint angle What is the operation for one quaternion for the lower arm and for the upper arm ? And how to find flexion extension or pronation supination ?

@Positive_Altitude

3 ай бұрын

Hey, I looked up these terms. It does not seem to be related to quaternions directly. So I don't think I can help with that.

Nice video. Do you can make some example application in robotic? Thanks 🙏🏽😊

@Positive_Altitude

Ай бұрын

Well, you can check out the video about the TVC model rocket. The attitude estimation/correction system was built with quaternions and formulas I have covered. And it's probably can be considered "robotics" :) Same goes for any drone / UAV or for example describing orientation of the robotic arm end effector.

Hey Amazing content. Wondering What path do you recommend to a newbie like me trying to getting into this Thanks

@Positive_Altitude

5 ай бұрын

Hey! What exactly are you interested in?

@mexitechnology7838

5 ай бұрын

@@Positive_Altitude Rockets

@Positive_Altitude

5 ай бұрын

Sorry. I forgot to answer :( I would start with understanding the basic physics of rocket flight. Like rocket stability (for regular aerodynamically stable rockets). Also how rockets are usually constructed, and what materials are commonly used. Then maybe try to build/launch a simple rocket! Also, check out r/rocketry subReddit -- there is a lot of information on that topic and you also can ask your questions and maybe get some help!

@mexitechnology7838

5 ай бұрын

@@Positive_Altitude Thank you so much will keep an eye on your content

❤

@11:15 what does 'tmp' stand for? I don't understand the errors that arise without normalization (the rocket getting bigger and bigger).... what causes that to happen and why does that normalization equation fix it? Is this similar to 'renormalization' in physics?

@Positive_Altitude

2 ай бұрын

'tmp' stands for 'temporary'. This formula is an approximation and it makes the norm to slightly increase with each step. I mentioned that rotation quaternions should be normalized, but actually, you can use non-normalized quaternions with the same math to transform coordinates. But in this case, you will not only rotate the space, but also you will scale it by the factor equal to the quaternion's norm. That's why if we let the quaternion's norm increase, the object gets bigger. To explain why exactly this happens I will give you a very similar example: Imagine that we are trying to draw a circle, but we can draw only short straight lines. And we use an algorithm: 1) Draw a line from the current point to the center (a radius) 2) Draw a short line perpendicular to this radius 3) The end of this short line is the next point of the circle 4) Go to 1) If we do this with very short lines this kinda works, but actually, every new point will be slightly further away from the center, and the radius will increase with each step. And if we keep doing it we will draw a spiral instead of a circle. If our steps are small it will spiral out slowly. With bigger steps, the problem gets worse. But we can fix that. After each step, we can make a little step toward the center that will make the current radius equal to the desired radius. That is exactly what normalization does. This example is VERY close to what happens with quaternions and this formula. In the case of quaternions, it's just a trajectory (not really a circle) in 4-dimensional space which I personally struggle to imagine. No, this is unrelated to renormalization. This is just us fixing an error caused by using approximation.

@erawanpencil

2 ай бұрын

@@Positive_Altitude Thank you, I think I'm getting it. The normalization sort of re-orients or self-orients the origin point of the gyroscope, the center of all the angular velocities right? That's why when you turned normalization off, it sort of dilated in-and-out/breathed like a growing spiral?

@erawanpencil

2 ай бұрын

@@Positive_Altitude Do you need to renormalize all quaternions or only gyroscopic ones with angular velocity? Does angular velocity add more requirements to make it work?

@Positive_Altitude

2 ай бұрын

@@erawanpencil I would not say that it "re-orients" it just scales it. Norm is literally a length and all proper rotation quaternions should have the length = 1. We just fix the error caused by this formula that makes quaternion slightly longer than it is supposed to be. Usually, when we just combine rotations there is no need to normalize quaternions. Because if we have two normalized quaternions, their product will be a normalized quaternion too. But also there is no harm in normalization. If you normalize a quaternion that is already normalized it will not change it. The angular velocity formula is just kinda weird. Mathematically it is obtained with the assumption that time step dt is "infinitely small". But there is no such thing as an infinitely small number when we do 3D graphics or iterative simulations. So in real life, this formula produces a small error both in direction (orientation) and length (norm). To deal with that we need 1) use as small dt as we can, to minimize the error in orientation 2) normalize quaternion to always keep norm = 1 as it is supposed to be

9:37 Why is the first one (alpha) same formula as last one (gamma)?

@Positive_Altitude

Ай бұрын

This is because we use ZYZ Euler scheme in this example. "ZYZ scheme" means that we make a sequence of 3 rotations around local axes 1) by alpha around Z; 2) by beta around Y 3) by gamma around Z. You might be thinking "why do we rotate twice around Z?" It works because each rotation is done in the local reference frame whose orientation is also changed with each rotation. So the first Z rotation is not the same as the last one, because when we do the last rotation, the reference frame is re-oriented by the first and second rotations. But because the first and third rotations are both rotate around local Z, the formulas are the same. To calculate q_gamma for example, I am using the formula explained at 4:40. In this case vector V = (0, 0, 1) because it is a normalized vector aligned with Z axis and theta = gamma. So just using this formula you will get all formulas shown at 9:37 Hope that helped :)

I have no idea how to use quaternions for Maya...

Видео ис зе бест ин кватернион эриа :)

Научись произносить звуки "th". Это значительно улучшит речь.

Хард рашен акцент!

@Positive_Altitude

6 ай бұрын

Come on, it's not THAT bad ;)

@user-jb1nb6en4z

6 ай бұрын

@@Positive_Altitude шутка, все ок, все понятно)

I dont understand any of this and im usually quite good with both technical and math stuff. 😞

@Positive_Altitude

2 ай бұрын

Sorry to hear that :( Is there anything I can help with?

Dafuq is React doing there 😂

@Positive_Altitude

Ай бұрын

lol