How can I flip the +/- direction of a single axis in a pose?
i want Z to go upwards, not downwards..
Thanks
If you want the z-axis goes upwards, you should apply a composing between that pose you're getting and another pose who has 180° (positive or negative) in the X or Y axis (any of both will work). If I try to emulate you posing, you should have something like next:
If you apply the composing I just said, you will get something like next:
The second image was achieved with a 180° rotation over X-Axis. The code was just:
create_pose (0, 0, 0, 0, 0, 0, 'Rp+T', 'gba', 'point', yourPose)
create_pose (0, 0, 0, 180, 0, 0, 'Rp+T', 'gba', 'point', transformationPose)
pose_compose (yourPose, transformationPose, transformedPose)
Remember, you would have 4 options for achieving the purpose of having Z-Axis upwards; +180° rotation in X-Axis, -180° rotation in X-Axis, +180° rotation in Y-Axis and -180° rotation in Y-Axis.
Related
I have written a script in Unity which takes a SkinnedMeshRenderer and AnimationClip and rotates the vertices in each by a specified number of degrees. It looks mostly correct except that rotations seem to be incorrect. Here is an example bone rotation (in euler angles) in the skeleton along with the correct values that would be needed for the animation to look correct.
With no rotation: (0, 0, -10)
Rotated 90 degrees: (-10, 0, 0)
Rotate 180 degrees: (0, 0, 10)
I have been trying to find a way to rotate these bones to make this conversion make sense with the data I have here, but have come up short. I know I want to rotate these values around the Y axis, but don't actually want the Y value in the euler angle to change. I am aware I could just reorient the root bone around the Y axis and the problem would be solved, but I want to have no rotation in the Y axis. I am "fixing" some older animations that have unnecessary rotation values in them.
var localBoneRotation = new Quaternion(keysX[j].value, keysY[j].value, keysZ[j].value, keysW[j].value).eulerAngles;
var reorientedForward = Quaternion.AngleAxis(rotation, Vector3.up) * Vector3.forward;
localBoneRotation.x *= reorientedForward.x;
localBoneRotation.y *= reorientedForward.y;
localBoneRotation.z *= reorientedForward.z;
var finalRotation = Quaternion.Euler(localBoneRotation);
keysX[j].value = finalRotation.x;
keysY[j].value = finalRotation.y;
keysZ[j].value = finalRotation.z;
keysW[j].value = finalRotation.w;
I have also tried using a matrix and Vector3 but most of the time I end up with values in the Y. Perhaps I am going about this incorrectly. I just need to be able to specify an angle rotation and then have the input data match the final euler angles with each of these data points.
I'm getting confused.
Using vision, I transform bottom-left coordinates to top-left by
CGAffineTransform(scaleX: 1, y: -1).translatedBy(x:0, y: -1)
however to rotate the camera view according to the orientation I
CGAffineTransform(translationX: 1, y: 0), rotated(by: -CGFloat.pi / 2)
why in the second case do we use CGAffineTransform(translationX... rather than CGAffineTransform(scaleX..
What is the difference between the two?
So why to transform bottom-left coordinates to top left do we use scale
So your question really is: Why is
CGAffineTransform(scaleX: 1, y: -1).translatedBy(x:0, y: -1)
the way to flip?
Let's start with the scale part. Scaling the y coordinate system to -1 is a multiplication: it reverses the scale so that up is down. That's the flip. (Scaling the x to 1 just means "leave it alone".)
The translate part is because transforms take place around the origin (the bottom left corner, originally). So when we flip by scaling, we flip ourselves right off the screen. In order to compensate for that, we slide back onto the screen.
They have a completely different meaning from each other, as per Apple doc:
.translatedBy
Returns an affine transformation matrix constructed by translating an
existing affine transform.
.scaledBy
Returns an affine transformation matrix constructed by scaling an
existing affine transform.
This Question was posted, but never answered.
Similar to This Question, I am trying to understand SCNNode.rotation as a 4D vector. The prior question utilizes an example that only manipulates 1 axis, i.e.,
SCNNode.rotation = (0, 0, 1, degToRad(45)) //Rotate about z-axis by 45 degrees
which makes sense; however, what if I wanted to rotate the X axis by 20 degrees, Y axis by 45 degrees and then Z axis by 78 degrees?
SCNNode.rotation = ??
I would provide code I've tried, but I don't understand conceptually the notion of a 4D rotation vector.
Every node just has a transform with 4x4 matrix. So all the rotation operations are reflecting in the changing the transform.
In this case, if you change either of rotation, eulerAngles and orientation, you are supposed to get same value.
If rotating about three axises, I suggested using eulerAngles.
node.eulerAnges = SCNVector3(x:degToRad(20),y:degToRad(45), z:degToRad(78))
After you set this, go back and check to value of rotation:
SCNVector4(x: -0.16975601, y: 0.5943193, z: 0.786109, w: 1.448788)
This means there is an axis going through point(-0.16975601, 0.5943193, 0.786109) and origin (0,0,0), and node is rotating around it for 1.448788 (82 degree).
This can be reproduced using the default Xcode 3D game template (SpaceShip).
Remove the runAction line that rotates the ship in the GameViewController.
Add this line. The ship correctly faces away from the camera.
Note the very small x component in the at: parameter.
ship.look(at: SCNVector3(0.001, 0, -100.0), up: SCNVector3(0, 1, 0), localFront: SCNVector3(0, 0, 1)) // Works! Ship faces away from camera.
However, it the x component of the at: parameter is exactly zero, the ship's orientation does not change. The ship continues to face the camera instead of facing away from it.
ship.look(at: SCNVector3(0, 0, -100.0), up: SCNVector3(0, 1, 0), localFront: SCNVector3(0, 0, 1)) // DOES NOT work
Seeing the same problem with simdLook()
For starters, if you show the world origin sceneView.debugOptions = ARSCNDebugOptions.showWorldOrigin], you will see that the x and y axis are actually opposite to what they would normally be, i.e. x is now y and y is now x.
Second, you are changing the x axis and not z axis. If you want the spaceship to look away or at you, that runs along the z axis. Negative(-) z will look at you where Positive(+)z will look away from you. Trying just changing the -100 to +100.
I have below information like gravity, thrust, my initial x, y and initial velocities. How do I calculate
1. Time to reach the top of the projectile 2. Horizontal displacement during that time
"grav": 0.7,
"thrust": 10.5,
"me": {
"x": 0,
"y": 180,
"vx": 4,
"vy": 0
}
So far I have tried this formula to calculate vertical displacement (reference here)
For Horizontal displacement, I used t*vx0;
If initial vertixal velocity(vy) is zero, assuming gravity is on the y direction, then how is the object ever going to go up to reach the top?
Generally thrown objects reach the top when vy = 0 when t= vy/grav, and x position = t * vx.