Away3D Forum Camera Rotation and Gimbal Lock

Beek, Member
Posted: 08 March 2015 04:04 AM Total Posts: 67

HI,

I’m attempting to manipulate some controls based on the camera roll (z).

The camera is controlled by device motion and a Quaternion. Anything I do to access this Quaternion, copying it, cloning it etc seems to change how it’s applied to the camera, so I decided to read the data from the camera itself.

At first just getting camera.rotationZ seemed OK, however it soon transpired when the camera is rotated around the Y axis the X and Z flip. So I did some crazy hacks to get around that:

var z = camera.rotationZ;
      var x = camera.rotationX;
      var x = camera.rotationY;

    z = z > 90 
     ? 0 - (z - 180)
     : z;
    z = z < - 90
     ? 0 - (z + 180)
     : z;
    
    x = x > 90 
     ? x - 180
     : x;
    x = x < - 90
     ? x + 180
     : x; 

Which is kind of working.

Now I’m stuck with what I’m assuming is a Gimble Lock, where if Y is near 90 or -90, X and Z go nuts and trigger my functions.

I assume it would be better to use the camera matrix, however converting that to Eulers seems to have the same affect.

I saw another post where someone created a matrix and applied each rotation in order with Y as the upVector, and this didn’t seem to help with this issue either.

Basically I want to catch if the camera has rolled 45 degrees either way, or is pointing straight down.

Any better way of achieving this?

JaykopX, Newbie
Posted: 08 March 2015 07:15 PM Total Posts: 13 [ # 1 ]

Basically I want to catch if the camera has rolled 45 degrees either way, or is pointing straight down.

If you mean with pointing straight down==“looking on the floor”
you can achieve this by checking the forwardVector of the camera:

var tolerance:Number = 0.1;
//checking how close we are to the looking-down-vector (0, -1, 0)
   if(Math.abs(view.camera.forwardVector.x) <= tolerance) {
    if(Math.abs(view.camera.forwardVector.z) <= tolerance) { 
     if(Math.abs(-view.camera.forwardVector.y-1) <= tolerance) {
      trace("Looking down");
     }
    }
   } 

where tolerance is between 1.0 and 0.0 and triggers the “look down” notification sooner(1.0==always) or later(0.0==only if exacly looking down).

For the rolling you could keep track of the leftVector. It should be a bit trickier, i maybe look into it.

Beek, Member
Posted: 08 March 2015 08:17 PM Total Posts: 67 [ # 2 ]

Worked perfectly thank you.

I’m checking the values of the leftVector to see if I can notice a pattern.

Thanks

EDIT

pano.camera.leftVector.y has the rotation value. This is so simple! I spent nearly all weekend fighting with that gimbal lock and flipping values.. thanks again.

Camera Rotation and Gimbal Lock Software: Away3D 4.x

Beek, Member Posted: 08 March 2015 04:04 AM Total Posts: 67 HI, I’m attempting to manipulate some controls based on the camera roll (z). The camera is controlled by device motion and a Quaternion. Anything I do to access this Quaternion, copying it, cloning it etc seems to change how it’s applied to the camera, so I decided to read the data from the camera itself. At first just getting camera.rotationZ seemed OK, however it soon transpired when the camera is rotated around the Y axis the X and Z flip. So I did some crazy hacks to get around that: `var z = camera.rotationZ; var x = camera.rotationX; var x = camera.rotationY; z = z > 90 ? 0 - (z - 180) : z; z = z < - 90 ? 0 - (z + 180) : z; x = x > 90 ? x - 180 : x; x = x < - 90 ? x + 180 : x;` Which is kind of working. Now I’m stuck with what I’m assuming is a Gimble Lock, where if Y is near 90 or -90, X and Z go nuts and trigger my functions. I assume it would be better to use the camera matrix, however converting that to Eulers seems to have the same affect. I saw another post where someone created a matrix and applied each rotation in order with Y as the upVector, and this didn’t seem to help with this issue either. Basically I want to catch if the camera has rolled 45 degrees either way, or is pointing straight down. Any better way of achieving this?
JaykopX, Newbie Posted: 08 March 2015 07:15 PM Total Posts: 13 [ # 1 ] Basically I want to catch if the camera has rolled 45 degrees either way, or is pointing straight down. If you mean with pointing straight down==“looking on the floor” you can achieve this by checking the forwardVector of the camera: `var tolerance:Number = 0.1; //checking how close we are to the looking-down-vector (0, -1, 0) if(Math.abs(view.camera.forwardVector.x) <= tolerance) { if(Math.abs(view.camera.forwardVector.z) <= tolerance) { if(Math.abs(-view.camera.forwardVector.y-1) <= tolerance) { trace("Looking down"); } } }` where tolerance is between 1.0 and 0.0 and triggers the “look down” notification sooner(1.0==always) or later(0.0==only if exacly looking down). For the rolling you could keep track of the leftVector. It should be a bit trickier, i maybe look into it.
Beek, Member Posted: 08 March 2015 08:17 PM Total Posts: 67 [ # 2 ] Worked perfectly thank you. I’m checking the values of the leftVector to see if I can notice a pattern. Thanks EDIT pano.camera.leftVector.y has the rotation value. This is so simple! I spent nearly all weekend fighting with that gimbal lock and flipping values.. thanks again.

Camera Rotation and Gimbal Lock

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