5 ms·

3D Rotation Design

147 points by fisian 2y ago

esperent 2y ago
Interesting but lacking some information. First up, of course, most people are familiar with rotating the camera rather than a single object. This is how most 3d viewers work, even if the orbit point is locked to the center of an object (e.g. in a 3d product display). So it's important to specific which we're talking about in an introductory article on 3d rotation methods. But, ok. We're talking about schemes to rotate a single object rather than the camera. The turntable controls they talk about are a special case of gimbal controls where we lock rotation to one or two axes. But in my personal experience, when it's two or three axes people still call it gimbal controls whereas turntable controls is rotation in a single axis (as if on a turntable, hence the name). But then again, 3d terminology is so mixed up across different fields that maybe some people have only heard the two axes version called a turntable. Not a big deal, but why no mention at all of gimbal controls? Then, trackballs. In my experience, when it's limited to a single hemisphere of rotation, these are called arcball controls. Trackballs are supposed to emulate a trackball mouse which don't have this limitation. And finally, no mention at all of the dreaded gimbal lock (where two of axes end up overlaid on each other and the controls loses a degree of freedom), which is a major reason for choosing one type over another. Overall, not an amazing article. I checked it again to see if I missed anything and realized it's a blog post for some app - so, basically an ad - which probably explains the lack of effort.
- xeonmc 2y ago
  Gimbal lock purely a consequence of implementation detail, completely independent from the three modes of interaction. Otherwise, I agree with the rest of your comment.
- jobigoud 2y ago
  Yeah the very first comparison in the article between Blender and Mesh lab is mixing camera rotation vs object rotation. It's also missing the absolute most natural user interface for rotating objects, which is when you are in VR or with hand tracking. If you have only one hand controller you attach the object to it so you can simply inspect it under any angle, and if you have two-hand tracking you can have translation, scale and rotation based on a virtual segment between the hands. The little Leap motion device worked like this it was very natural.
- adrian_b 2y ago
  > Trackballs are supposed to emulate a trackball mouse which don't have this limitation. Some systems implement a trackball UI that behaves like a real trackball, i.e. it also has inertia, so you can give an impulse towards a direction and the 3D model will continue to rotate after you no longer click the mouse button, until you stop the rotation. I do not remember using any trackball UI where the rotation was limited. When the trackball UI did not have inertia, than you would need to do 3 pushes for a rotation over 360 degrees or 2 pushes for a rotation over 180 degrees, but you could still reach any angles.
- nkrisc 2y ago
  Gimbal lock happens based on how you calculate the rotations, and it could happen to both these methods if you do it incorrectly. It is not inherent to any particular style of translating user input into a rotation.
moffkalast 2y ago
I never understood why most CAD software prefers the tumbler style rotation, it's so completely horrid to use. I guess lots of people (somehow) got used to it without knowing there's an alternative?
- the__alchemist 2y ago
  It's more flexible. For example, compare the "Turnable" and "Tumbler" rotations in the article; you will be able to set arbitrary orientations in the latter, but not the former.
  - moffkalast 2y ago
    More like you are accidentally forced into arbitrary rotations with the tumbler, because of how moves correspond to inconsistent axes depending on the way you're turned. Honestly I don't see that supposed failing as much of a downside really, because A) most of those extra rotations don't change the camera view in any meaningful way, they just roll it, B) you can typically rotate the object on top of the camera if you really need these rotations, and C) it makes control much more accurate.
    - the__alchemist 2y ago
      I think the "turnable" approach would be fine if it included an extra roll control. Probably preferable due to the ease you point out; this overcomes the limit you point out. My personal preference, and how I've set up my visualization engine (For chemistry vis projects and similar): Move the camera; not the object. FPV controls, plus a roll axis, with crouch/jump for up/down. Works best with a videogame controller, but FPS standard + Q/E is fine too! Full control, and intuitive if you've played those sorts of games. This is full 6 axis.
    - djmips 2y ago
      See circle trick comments elsewhere or briefed under your top post.
- Karliss 2y ago
stogot 2y ago
I used to spend hours reading source code for 3D designs such as this. And sometimes having to reverse it. I like these systems a lot
xeonmc 2y ago
For freely rotated objects, trackball rotation is only ever appropriate for touch screens, mice should use tumbler instead so that you don't have to pay attention to the absolute position of the cursor.
- MaxikCZ 2y ago
  Even on mobile it struck me immediatelly that I cant rotate the trackball example as much as Id like without trying again.
phkahler 2y ago
I once implemented tumbler, but always used the starting position and current position to determine the rotation. This make it behave the same way when the mouse follows a straight path, but also makes it path independent.
dllu 2y ago
> There's another, more subtle critique of this system: it lacks path independence. This means that if you start and end a drag with your mouse at a particular location, the rotation will depend on the path that your mouse took. Actually, when I accidentally tumble models with that kind of UI, I just drag it in a circle until it's right side up.
- tanvach 2y ago
  I accidentally found how to do this while using a solid modeling software and use it quite a bit. I don’t see a formal name for this maneuver, or anyone teaching it. ‘Gimbal tumbling’ is the closest description.
- IshKebab 2y ago
  Yeah I will fully admit that "draw circles to yaw" is not intuitive or discoverable, but it is quite convenient when you have learnt it. I'd definitely prefer tumbler over trackball because of this. But turntable is clearly far superior to the others. Unless you really need to yaw the model then stick with that.
- djmips 2y ago
  Thanks for that tip! Works very well checking with the blogpost.
xg15 2y ago
I wonder if better rotation modes would be possible with multitouch inputs, I.e. using two "touch points" instead of one. Then you could span a plane between the two points and the origin and use this to better derive the user's intention which axes should be rotated.
- pfranz 2y ago
  This is unrelated to viewport rotation, but I've always wanted to play with multiple inputs for posing characters. There was always a lot of interest in "full body IK" which seems like a similar idea to me. Both IK and FK imply there's an anchor point and your single (mouse) input is posing the model. With two inputs it would be more like posing a puppet where one hand anchors and the other moves. You would still have to figure out how to deal with interpolation between poses, but I would imagine posing would be more intuitive.
W0lf 2y ago
Isn’t arcball rotation the gold standard for rotating 3d objects?
- romwell 2y ago
  Yes, and it has the path independence property, as well as the ability to arrive at any orientation with a single drag. But hey, most implementations talk about using quaternions, which scare people. And so the author of the article (...and a lot of software) is completely ignorant of how e.g. 3DS Max, Maya, etc do it. FWIW, here's a proper arc ball implementation. Try it vs. your favorite 3D software, and by God, implement it in yours: (Demo requires mouse) https://romankogan.net/math/arcball_js/index.html https://romankogan.net/math/arcball_js/index.html
gwking 2y ago
The trackball implementation appears to have a numerical bug in it. Occasionally (on mac safari at least) the rendering will be blank white. If you happen to let go of the mouse during that frame, then it gets permanently stuck and requires a page refresh. Seems like it might be a divide by zero due to a small cursor delta or something along those lines.
bvrmn 2y ago
> it's impossible to see the model from arbitrary angles I don't understand this part. I could easily see all 6 faces with turntable. Does it really matters to be able to make arbitrary rotations?
sgnelson 2y ago
FYI, from 2017. Also, Matt Keeter has some serious skills. I always thought his Antimony CAD program[1] was neat, and sad that it seems to have died. I've yet to figure out how to get it to run on newer versions of linux (The last time I tried was about 3 years ago, and I was just using a raspberry pi.) [1] https://www.mattkeeter.com/projects/antimony/3/ https://www.mattkeeter.com/projects/antimony/3/
- Duanemclemore 2y ago
  Very cool. If you like this check out the Grasshopper visual programming environment inside Rhino3d. It's also a node-based graph editor and has an extremely robust library developer community [0]. One of which I actually am. [0] https://www.food4rhino.com/en/ https://www.food4rhino.com/en/
scotty79 2y ago
Turntable does pitch on x and yaw on y. I wonder if you could achieve something like the last "spherical" solution if you did on y a combination of yaw and roll dependant on how far is your cursor from the x-center of the rotation.

147 points by fisian 2y ago

Interesting but lacking some information. First up, of course, most people are familiar with rotating the camera rather than a single object. This is how most 3d viewers work, even if the orbit point is locked to the center of an object (e.g. in a 3d product display). So it's important to specific which we're talking about in an introductory article on 3d rotation methods. But, ok. We're talking about schemes to rotate a single object rather than the camera. The turntable controls they talk about are a special case of gimbal controls where we lock rotation to one or two axes. But in my personal experience, when it's two or three axes people still call it gimbal controls whereas turntable controls is rotation in a single axis (as if on a turntable, hence the name). But then again, 3d terminology is so mixed up across different fields that maybe some people have only heard the two axes version called a turntable. Not a big deal, but why no mention at all of gimbal controls? Then, trackballs. In my experience, when it's limited to a single hemisphere of rotation, these are called arcball controls. Trackballs are supposed to emulate a trackball mouse which don't have this limitation. And finally, no mention at all of the dreaded gimbal lock (where two of axes end up overlaid on each other and the controls loses a degree of freedom), which is a major reason for choosing one type over another. Overall, not an amazing article. I checked it again to see if I missed anything and realized it's a blog post for some app - so, basically an ad - which probably explains the lack of effort.

xeonmc 2y ago
Gimbal lock purely a consequence of implementation detail, completely independent from the three modes of interaction. Otherwise, I agree with the rest of your comment.
jobigoud 2y ago
Yeah the very first comparison in the article between Blender and Mesh lab is mixing camera rotation vs object rotation. It's also missing the absolute most natural user interface for rotating objects, which is when you are in VR or with hand tracking. If you have only one hand controller you attach the object to it so you can simply inspect it under any angle, and if you have two-hand tracking you can have translation, scale and rotation based on a virtual segment between the hands. The little Leap motion device worked like this it was very natural.
adrian_b 2y ago
> Trackballs are supposed to emulate a trackball mouse which don't have this limitation. Some systems implement a trackball UI that behaves like a real trackball, i.e. it also has inertia, so you can give an impulse towards a direction and the 3D model will continue to rotate after you no longer click the mouse button, until you stop the rotation. I do not remember using any trackball UI where the rotation was limited. When the trackball UI did not have inertia, than you would need to do 3 pushes for a rotation over 360 degrees or 2 pushes for a rotation over 180 degrees, but you could still reach any angles.
nkrisc 2y ago
Gimbal lock happens based on how you calculate the rotations, and it could happen to both these methods if you do it incorrectly. It is not inherent to any particular style of translating user input into a rotation.

moffkalast 2y ago

I never understood why most CAD software prefers the tumbler style rotation, it's so completely horrid to use. I guess lots of people (somehow) got used to it without knowing there's an alternative?

the__alchemist 2y ago
It's more flexible. For example, compare the "Turnable" and "Tumbler" rotations in the article; you will be able to set arbitrary orientations in the latter, but not the former.
- moffkalast 2y ago
  More like you are accidentally forced into arbitrary rotations with the tumbler, because of how moves correspond to inconsistent axes depending on the way you're turned. Honestly I don't see that supposed failing as much of a downside really, because A) most of those extra rotations don't change the camera view in any meaningful way, they just roll it, B) you can typically rotate the object on top of the camera if you really need these rotations, and C) it makes control much more accurate.
  - the__alchemist 2y ago
    I think the "turnable" approach would be fine if it included an extra roll control. Probably preferable due to the ease you point out; this overcomes the limit you point out. My personal preference, and how I've set up my visualization engine (For chemistry vis projects and similar): Move the camera; not the object. FPV controls, plus a roll axis, with crouch/jump for up/down. Works best with a videogame controller, but FPS standard + Q/E is fine too! Full control, and intuitive if you've played those sorts of games. This is full 6 axis.
  - djmips 2y ago
    See circle trick comments elsewhere or briefed under your top post.
Karliss 2y ago

stogot 2y ago

I used to spend hours reading source code for 3D designs such as this. And sometimes having to reverse it. I like these systems a lot

xeonmc 2y ago

For freely rotated objects, trackball rotation is only ever appropriate for touch screens, mice should use tumbler instead so that you don't have to pay attention to the absolute position of the cursor.

MaxikCZ 2y ago
Even on mobile it struck me immediatelly that I cant rotate the trackball example as much as Id like without trying again.

phkahler 2y ago

I once implemented tumbler, but always used the starting position and current position to determine the rotation. This make it behave the same way when the mouse follows a straight path, but also makes it path independent.

dllu 2y ago

> There's another, more subtle critique of this system: it lacks path independence. This means that if you start and end a drag with your mouse at a particular location, the rotation will depend on the path that your mouse took. Actually, when I accidentally tumble models with that kind of UI, I just drag it in a circle until it's right side up.

tanvach 2y ago
I accidentally found how to do this while using a solid modeling software and use it quite a bit. I don’t see a formal name for this maneuver, or anyone teaching it. ‘Gimbal tumbling’ is the closest description.
IshKebab 2y ago
Yeah I will fully admit that "draw circles to yaw" is not intuitive or discoverable, but it is quite convenient when you have learnt it. I'd definitely prefer tumbler over trackball because of this. But turntable is clearly far superior to the others. Unless you really need to yaw the model then stick with that.
djmips 2y ago
Thanks for that tip! Works very well checking with the blogpost.

xg15 2y ago

I wonder if better rotation modes would be possible with multitouch inputs, I.e. using two "touch points" instead of one. Then you could span a plane between the two points and the origin and use this to better derive the user's intention which axes should be rotated.

pfranz 2y ago
This is unrelated to viewport rotation, but I've always wanted to play with multiple inputs for posing characters. There was always a lot of interest in "full body IK" which seems like a similar idea to me. Both IK and FK imply there's an anchor point and your single (mouse) input is posing the model. With two inputs it would be more like posing a puppet where one hand anchors and the other moves. You would still have to figure out how to deal with interpolation between poses, but I would imagine posing would be more intuitive.

W0lf 2y ago

Isn’t arcball rotation the gold standard for rotating 3d objects?

romwell 2y ago
Yes, and it has the path independence property, as well as the ability to arrive at any orientation with a single drag. But hey, most implementations talk about using quaternions, which scare people. And so the author of the article (...and a lot of software) is completely ignorant of how e.g. 3DS Max, Maya, etc do it. FWIW, here's a proper arc ball implementation. Try it vs. your favorite 3D software, and by God, implement it in yours: (Demo requires mouse) https://romankogan.net/math/arcball_js/index.html https://romankogan.net/math/arcball_js/index.html

gwking 2y ago

The trackball implementation appears to have a numerical bug in it. Occasionally (on mac safari at least) the rendering will be blank white. If you happen to let go of the mouse during that frame, then it gets permanently stuck and requires a page refresh. Seems like it might be a divide by zero due to a small cursor delta or something along those lines.

bvrmn 2y ago

> it's impossible to see the model from arbitrary angles I don't understand this part. I could easily see all 6 faces with turntable. Does it really matters to be able to make arbitrary rotations?

sgnelson 2y ago

FYI, from 2017. Also, Matt Keeter has some serious skills. I always thought his Antimony CAD program[1] was neat, and sad that it seems to have died. I've yet to figure out how to get it to run on newer versions of linux (The last time I tried was about 3 years ago, and I was just using a raspberry pi.) [1] https://www.mattkeeter.com/projects/antimony/3/ https://www.mattkeeter.com/projects/antimony/3/

Duanemclemore 2y ago
Very cool. If you like this check out the Grasshopper visual programming environment inside Rhino3d. It's also a node-based graph editor and has an extremely robust library developer community [0]. One of which I actually am. [0] https://www.food4rhino.com/en/ https://www.food4rhino.com/en/

scotty79 2y ago

Turntable does pitch on x and yaw on y. I wonder if you could achieve something like the last "spherical" solution if you did on y a combination of yaw and roll dependant on how far is your cursor from the x-center of the rotation.