I am learning SceneKit and trying to get the tip of a cone to point at the another node (a capsule) that is bouncing. Regardless of using the .orient on the cone, as soon as the SCNLookAtConstraint call gets made it re-orients the cone to the standard upright position so that the cone tip point straight up along the Y axis again and rock left and right as opposed to pointing its tip to the moving capsule which is to the rightof the cone. I tried changing the .pivot of the cone as well but that just seems to change the anchor point of the pivot but does not change the orientation of the cone.I need something like a SCNLookAtConstraint that indicates what point of the cone looks at the capsule?
Thanks
the pivot property is the way to go. It allows you to change the anchor point, but also its orientation since its a transform.
Related
I built a complete structure as a node (with its child nodes) and the user will walk through it using ARKit.
At some point, if the user cannot continue because of some real obstacle in the real world, I added a "pause" button which should freeze whatever the user currently sees in front of the camera, the user could then move freely to some other open space and when the user will release the pause button he/she will be able to resume where they left off (only someplace else in the real world).
A while ago I asked about it in the Apple Developer forum and an Apple Frameworks Engineer gave the following reply:
For "freezing" the scene, you could transform the anchor's position (in world coordinates) to camera coordinates, and then anchor your content to the camera. This will give you the effect that the scene is "frozen", i.e., does not move relative to the camera.
I'm currently not using an anchor because I don't necessarily need to find a flat surface. Rather, my node is placed at a certain position relative to where we start at (0,0,0).
My question is how do I exactly do what the Apple engineer told me to do?
I have the following code which I'm still stuck with. When I add the node to the camera (pointOfView, last line of the code below), it does freeze in place, but I can't get it to freeze in the same position and orientation as it was before it was frozen.
#IBAction func pauseButtonClicked(_ sender: UIButton) {
let currentPosition = sceneView.pointOfView?.position
let currentEulerAngles = sceneView.pointOfView?.eulerAngles
var internalNodeTraversal = lastNodeRootPosition - currentPosition! // for now, lastNodeRootPosition is (0,0,0)
internalNodeTraversal.y = lastNodeRootPosition.y + 20 // just so it’s positioned a little higher in front of the camera
myNode?.removeFromParentNode() // remove the node from the Real World view. Looks like this line has no effect and just adding the node as a child to the camera (pointOfView) is enough, but it feels more right to do this anyway.
myNode?.position = internalNodeTraversal // the whole node is moved respectively in the opposite direction from the root to where I’m standing to reposition the camera in my current position inside the node
// myNode?.eulerAngles = (currentEulerAngles! * -1) — this code put the whole node in weird positions so I removed it
myNode?.eulerAngles.y = currentEulerAngles!.y * -1 // opposite orientation of the node so the camera will be oriented in the same direction
myNode?.eulerAngles.x = 0.3 // just tilting it up a little bit to have a better view, more similar to the view as before it was locked to the camera
// I don’t think I need to change the eulerAngles.z
myNode!.convertPosition(internalNodeTraversal, to: sceneView.pointOfView) // I’m not sure I wrote this correctly. Also, this line doesn’t seem tp change anything
sceneView.pointOfView?.addChildNode(myNode!) // attaching the node to the camera so it will remain stuck while the user moves around until the button is released
}
So I first calculate where in the node I'm currently standing and then I change the position of the node in the opposite direction so that the camera will now be in that position. That seems to be correct.
Now I need to change the orientation of the node so that it will point in the right direction and here things get funky. I've been trying so many things for days now.
I use the eulerAngles for the orientation. If I set the whole vector multiplied by -1, it would show weird orientations. I ended up only using the eulerAngles.y which is the left/right orientation and I hardcoded the x orientation (up/down).
Ultimately what I have in the code above is the closest that I was able to get. If I'm pointing straight, the freeze will be correct. If I turn just a little bit, the freeze will be pretty close as well. Almost the same as what the user saw before the freeze. But the more I turn, the more the frozen image is off and more slanted. At some point (say I turn 50 or 60 degrees to the side) the whole node is off the camera and cannot be seen.
Somehow I have a feeling that there must be an easier and more correct way to achieve the above.
The Apple engineer wrote to "transform the anchor's position (in world coordinates) to camera coordinates". For that reason I added the "convertPosition" function in my code, but a) I'm not sure I used it correctly and b) it doesn't seem to change anything in my code if I have that line or not.
What am I doing wrong?
Any help would be very much appreciated.
Thanks!
I found the solution!
Actually, the problem I had was not even described as I didn't think it was relevant. I built the AR nodes 2 meters in front of the origin (-2 for the z-coordinate) while the center of my node was still at the origin. So when I changed the rotation or eulerAngles, it rotated around the origin so my nodes moved in a large curve and in fact also changed their position as a result.
The solution was to use a simdPivot. Instead of changing the position and rotation of the node itself, I created a translation matrix and a rotation matrix which was at the point of the camera (where the user is standing) and I then multiplied both matrices. Now when I added the node as a child of the camera (pointOfView) this would freeze the image and in effect show exactly what the user was seeing before it was frozen as the position is the same and the rotation is exactly around the user's standing position.
It seems HitResult only gives us intersection with a surface (plane) or a point cloud. How can I get a point in the middle of air with my click, and thus put an object floating in the air?
It really depends on what you mean by "in the air". Two possibilities I see:
"Above a detected surface" Do a normal hit test against a plane, and offset the returned pose by some Y distance to get the hovering location. For example:
Pose.makeTranslation(0, 0.5f, 0).compose(hitResult.getHitPose())
returns a pose that is 50cm above the hit location. Create an anchor from this and you're good to go. You also could just create the anchor at the hit location and compose with the y translation each frame to allow for animating the hover height.
"Floating in front of the current device position" For this you probably want to compose a translation on the right hand side of the camera pose:
frame.getPose().compose(Pose.makeTranslation(0, 0, -1.0f)).extractTranslation()
gives you a translation-only pose that is 1m in front of the center of the display. If you want to be in front of a particular screen location, I put some code in this answer to do screen point to world ray conversion.
Apologies if you're in Unity/Unreal, your question didn't specify so I assumed Java.
The reason why you see so often a hit result being interpreted as the desired position by the user is that actually there is no closed-form solution for this user interaction. Which of the infinite possible positions along the ray starting from the camera pointing towards the scene was desired by the User? 2D coordinates from a click still leave the third dimension undefined.
As you said "middle of the air", why not take the centre between the camera position and the hitresult?
You can extract the current position using pose.getTranslation https://developers.google.com/ar/reference/java/com/google/ar/core/Pose.html#getTranslation(float[],%20int)
I am developing a Ui which has a look & feel like a speedometer of vehicle which has a needle which is fixed from one end & rotate with some angle with that fixed end.
I have done some sort of code for that
self.SIV_Needle.transform =CGAffineTransformMakeRotation((CGFloat(M_PI_2)/180.0) * 80)
Its working but the imageView loss its original x & y coordinates from one end.I have tried lot of things like changing anchor point , center but doesn't seems to work well.
Responding to my comment, OP said the issue was that the control was not rotating around the desired axis. OP was not (I think) clear about what the desired axis is, nor about what the current axis is (I am using axis interchangeably to mean pivot point). There are a few potential fixes.
1) This needle thing is an ImageView, so you could do a simple hack and just make your image bigger or smaller to fix the rotation. To explain: if your needle is rotating around the center of the needle and not the ball part, then simply double the width of the image, such that the needle only takes up the right side and thus the "ball" of the needle is the pivot point.
2) Set the anchor property of the transform to wherever you want it to be rotating around. See this similar SO question & answer.
You need to translate the UI , to compensate the position change comes due to roatation
Try to change the anchor point of the needle imageView and then add the Rotation. I have not tried it, but i think it should work.
You can archive this by putting your pin image in a UIView at desired position and rotating your main UIView.
like;
let myView:UIIView = UIIView(); //set frame of UIView
let pinImgView:UIVImageView(); // set pin image and frame of required position
//--
myView.addSubview(pinImgView);
//--
myView.transform =CGAffineTransformMakeRotation((CGFloat(M_PI_2)/180.0) * 80);
I have made a sample project for this. you can take idea from it;
http://www.filedropper.com/stackover
or
http://wikisend.com/download/263926/StackOver.zip
I currently have a scene which contains a central node at the root of the scene with earth-like geometry and a node representing a flying vehicle.
However I cannot find the right approach to control the movement of the vehicle. I need the ability to turn left and right while orbiting at a static altitude and speed.
I have tried many combinations of animations and physics body forces all leading to undesirable results.
The closest I've come is:
Setting the pivot property of the vehicle to the centre of the scene
Then setting an Action like below to control moving forward
[_vehicleNode runAction:[SCNAction repeatActionForever:[SCNAction rotateByX:-1 y:0 z:0 duration:10.0]]];
Then finally applying forces for turning left and right with
[_vehicleNode.physicsBody applyTorque:SCNVector4Make(0, 1, 0, 1) impulse:YES];
However I cannot seem to set the pivot and/or position to the right value to get the desired result.
Edit: It appears as the above method would be the solution I'm looking for, however for some reason when I add geometry to the vehicle node, it's position in the scene graph gets changed dramatically. When I add hardcoded buttons to change it's position to where it belongs it appears correct for only that single frame then straight back to being in the middle of nowhere.
Edit 2: After replacing all geometry with a primitive sphere for testing the node is now rotating as intended but is now unaffected by physics forces appearing to ignore it's declaration as a dynamicBody.
If I understand what you are trying to achieve correctly, you can try this:
add a first node to your scene, positioned at (0,0,0) and make it rotate forever along the Y axis using an SCNAction
add your ship node as a child of the first node. Position it at (X,0,0) so that it orbits around the earth
rotate your ship node along the X axis with an action or an animation
I'm creating a car driving game for iOS, but there's a problem:
I added these lines to my ViewController.m:
_carView.transform = CGAffineTransformMakeRotation(steeringTemp-45);
steeringTemp is a float variable wich is changed by the left and right steering buttons.
But when I run the app and press the steering button, the car is rotating in an ugly way. It seems like the center point is changing everytime and the car is rotating like a triangle. I tried to set the origin to the center of the _carView, which is an image view, but it didn't work.
First of all let me tell you that you should be using radians, and not degrees. You can use this macro:
#define DEGREES_TO_RADIANS(angle) (angle * M_PI / 180.0)
And wrap it around your values:
CGAffineTransformMakeRotation(DEGRESS_TO_RADIANS(steeringTemp-45));
Second usually transforms go wrong if you:
Are rotating with the wrong anchorPoint (usually happens with clock pointers)
Don't pay attention to the order of transforms
Anchor Point
You need to make sure that your anchor point to the place you wanted. The anchorPoint defaults to the center, but you can set it to any point you like in the layer that is backed by the view. The anchor point has relative coordinates, so it goes from 0 to 1. (0,0) is your left top corner and (1,1) is your bottom right corner.
You can set it like this:
_carView.layer.anchorPoint = CGPointMake(0, 0);
Transforms order is important
Additionally, be careful if you apply more transforms you should pay attention to the order of those transforms. The previous transforms will always affect the next transforms. A rotation followed by a translation is way different than a translation followed by a rotation.