This is driving me crazy.
Im applying a scale transform, if I type numbers statically, it scales perfectly well. but if I use variables it always reset's to 1.0. But I even print the new transform and the scale is applied.
This works:
let scaleTransform = origTranform.scaledBy(x: 0.28125, y: 0.28125)
This doesn't
let s = finalVideoFrame.height/size.height;
let scaleTransform = origTranform.scaledBy(x: s, y: s)
if I print scaleTransform I get the right values on either cases.
▿ CGAffineTransform
- a : 0.28125
- b : 0.0
- c : 0.0
- d : 0.28125
- tx : 0.0
- ty : 0.0
Im using this transfom to set it for a AVMutableVideoCompositionLayerInstruction
Related
In my app I need some animation but if it already animated it doens't need to have a duration. But my problem is that it automatically adds a duration.
Here you can see 2 functions, second one is without duration but it really has a duration (from maybe 1 second) , the first function has a duration (and it should have and that's okay) but it isn't 0.6 seconds because if I set it on 30 it still animates very fast.
What am I doing wrong, thanks in advance!
func openMessage() {
UIView.animate(withDuration: 0.6, delay: 0.0, options: [], animations: {
var t = CATransform3DIdentity;
t = CATransform3DMakeRotation(CGFloat(3 * Float.pi / 4), 0, 0, 1)
self.moveableLineLayer.transform = t;
}, completion:{(finished:Bool) in })
}
func openMessageWithoutAnimation() {
self.moveableLineLayer.transform = CATransform3DIdentity
var t = CATransform3DIdentity;
t = CATransform3DMakeRotation(CGFloat(3 * Float.pi / 4), 0, 0, 1)
self.moveableLineLayer.transform = t;
}
Consider using the velocity parameter. From the documentation:
velocity
The initial spring velocity. For smooth start to the animation, match this value to the view’s velocity as it was prior to attachment.
A value of 1 corresponds to the total animation distance traversed in one second. For example, if the total animation distance is 200 points and you want the start of the animation to match a view velocity of 100 pt/s, use a value of 0.5.
I'm dynamically creating a 3D model and writing an .obj file. I'm having a problem with flipping the visible side of faces.
I've made a simple example:
v 0.0 0.0 0.0
v 0.0 1.0 0.0
v 1.0 0.0 0.0
v 1.0 1.0 0.0
vn 0.0 0.0 -1.0
f 1//1 4//1 3//1
f 1//1 2//1 4//1
The above is a square divided into two triangles. The vn line is the face normal (the vector that is perpendicular to the face). I've read online that to flip the face, you can negate the normal vector. However if I multiply the normal vector by -1 and try the following...
v 0.0 0.0 0.0
v 0.0 1.0 0.0
v 1.0 0.0 0.0
v 1.0 1.0 0.0
vn 0.0 0.0 1.0
f 1//1 4//1 3//1
f 1//1 2//1 4//1
It doesn't actually flip the visible side of the face when I import it into Unity. The lighting changes a little bit, but the same side is still visible and the other side is still invisible.
When I orbit to the opposite side:
The normal only influences the lighting effect. To flip a face, you need to inverse the index order of the triangle like below.
f 3//1 4//1 1//1
f 4//1 2//1 1//1
I'm working on a top-down space game built using Swift and SceneKit with the following setup:
SCNNode representing a spaceship
Rotation is constrained to the y axis; values range from -M_PI_2 to M_PI + M_PI_2
Movement is constrained to the x and z axes.
Game controller thumbstick input
Values range from -1.0 to 1.0 on the x and y axes.
When the game controller's thumbstick changes position, the spaceship should rotate using the physics body to match the thumbstick's radian.
The target radian of the thumbstick can be calculated with the following:
let targetRadian = M_PI_2 + atan2(-y, -x)
The current radian of the node can be obtained with the following:
let currentRadian = node.presentationNode.rotation.w * node.presentationNode.rotation.y
NSTimeInterval deltaTime provides the time in seconds since the last rotation calculation.
How can the node be rotated using angularVelocity, applyTorque, or another physics method to reach the targetRadian?
The difference between the targetRadian and the currentRadian ranged from 0.0 to -2π depending on the value of currentRadian. This equation will determine the shortest direction to turn, .Clockwise or .CounterClockwise, to reach the targetRadian:
let turnDirection = (radianDifference + (M_PI * 2)) % (M_PI * 2) < M_PI ? RotationDirection.CounterClockwise : RotationDirection.Clockwise
Using applyTorque, there is a possibility to over-rotate past the targetRadian resulting in a wobbling effect, like a compass magnetizing toward a point, as the rotation changes direction back and forth to reach the targetRadian. The following, while not a perfect solution, dampened the effect:
let turnDampener = abs(radianDifference) < 1.0 ? abs(radianDifference) : 1.0
The complete solution is thus:
enum RotationDirection: Double {
case Clockwise = -1.0
case CounterClockwise = 1.0
}
func rotateNodeTowardDirectionalVector(node: SCNNode, targetDirectionalVector: (x: Double, y: Double), deltaTime: NSTimeInterval) {
guard abs(targetDirectionalVector.x) > 0.0 || abs(targetDirectionalVector.y) > 0.0 else { return }
let currentRadian = Double(node.presentationNode.rotation.w * node.presentationNode.rotation.y)
let targetRadian = M_PI_2 + atan2(-targetDirectionalVector.y, -targetDirectionalVector.x)
let radianDifference = targetRadian - currentRadian
let π2 = M_PI * 2
let turnDirection = (radianDifference + π2) % π2 < M_PI ? RotationDirection.CounterClockwise : RotationDirection.Clockwise
let absRadianDifference = abs(radianDifference)
let turnDampener = absRadianDifference < 1.0 ? absRadianDifference : 1.0
node.physicsBody?.applyTorque(SCNVector4Make(0, CGFloat(turnDirection.rawValue), 0, CGFloat(deltaTime * turnDampener)), impulse: true)
}
I'm trying to display a pyramid that points following the z axis and then rotates on itself around z too.
As my camera is on the z axis, I'm expecting to see the pyramid from above. I managed to rotate the pyramid to see it this way but when I add the animation it seems to rotate on multiple axis.
Here is my code:
// The following create the pyramid and place it how I want
let pyramid = SCNPyramid(width: 1.0, height: 1.0, length: 1.0)
let pyramidNode = SCNNode(geometry: pyramid)
pyramidNode.position = SCNVector3(x: 0, y: 0, z: 0)
pyramidNode.rotation = SCNVector4(x: 1, y: 0, z: 0, w: Float(M_PI / 2))
scene.rootNode.addChildNode(pyramidNode)
// But the animation seems to rotate aroun 2 axis and not just z
var spin = CABasicAnimation(keyPath: "rotation")
spin.byValue = NSValue(SCNVector4: SCNVector4(x: 0, y: 0, z: 1, w: 2*Float(M_PI)))
spin.duration = 3
spin.repeatCount = HUGE
pyramidNode.addAnimation(spin, forKey: "spin around")
Trying to both manually set and animate the same property can cause issues. Using a byValue animation makes the problem worse -- that concatenates to the current transform, so it's harder to keep track of whether the current transform is what the animation expects to start with.
Instead, separate the fixed orientation of the pyramid (its apex is in the -z direction) from the animation (it spins around the axis it points in). There's two good ways to do this:
Make pyramidNode the child of another node that gets the one-time rotation (π/2 around x-axis), and apply the spin animation directly to pyramidNode. (In this case, the apex of the pyramid will still point in the +y direction of its local space, so you'll want to spin around that axis instead of the z-axis.)
Use the pivot property to transform the local space of pyramidNode's contents, and animate pyramidNode relative to its containing space.
Here's some code to show the second approach:
let pyramid = SCNPyramid(width: 1.0, height: 1.0, length: 1.0)
let pyramidNode = SCNNode(geometry: pyramid)
pyramidNode.position = SCNVector3(x: 0, y: 0, z: 0)
// Point the pyramid in the -z direction
pyramidNode.pivot = SCNMatrix4MakeRotation(CGFloat(M_PI_2), 1, 0, 0)
scene.rootNode.addChildNode(pyramidNode)
let spin = CABasicAnimation(keyPath: "rotation")
// Use from-to to explicitly make a full rotation around z
spin.fromValue = NSValue(SCNVector4: SCNVector4(x: 0, y: 0, z: 1, w: 0))
spin.toValue = NSValue(SCNVector4: SCNVector4(x: 0, y: 0, z: 1, w: CGFloat(2 * M_PI)))
spin.duration = 3
spin.repeatCount = .infinity
pyramidNode.addAnimation(spin, forKey: "spin around")
Some unrelated changes to improve code quality:
Use CGFloat when explicit conversion is required to initialize an SCNVector component; using Float or Double specifically will break on 32 or 64 bit architecture.
Use .infinity instead of the legacy BSD math constant HUGE. This type-infers to whatever the type of spin.repeatCount is, and uses a constant value that's defined for all floating-point types.
Use M_PI_2 for π/2 to be pedantic about precision.
Use let instead of var for the animation, since we never assign a different value to spin.
More on the CGFloat error business: In Swift, numeric literals have no type until the expression they're in needs one. That's why you can do things like spin.duration = 3 -- even though duration is a floating-point value, Swift lets you pass an "integer literal". But if you do let d = 3; spin.duration = d you get an error. Why? Because variables/constants have explicit types, and Swift doesn't do implicit type conversion. The 3 is typeless, but when it gets assigned to d, type inference defaults to choosing Int because you haven't specified anything else.
If you're seeing type conversion errors, you probably have code that mixes literals, constants, and/or values returned from functions. You can probably just make the errors go away by converting everything in the expression to CGFloat (or whatever the type you're passing that expression to is). Of course, that'll make your code unreadable and ugly, so once you get it working you might start removing conversions one at a time until you find the one that does the job.
SceneKit includes animation helpers which are much simpler & shorter to use than CAAnimations. This is ObjC but gets across the point:
[pyramidNode runAction:
[SCNAction repeatActionForever:
[SCNAction rotateByX:0 y:0 z:2*M_PI duration:3]]];
I changed byValue to toValue and this worked for me. So change the line...
spin.byValue = NSValue(SCNVector4: SCNVector4(...
Change it to...
spin.toValue = NSValue(SCNVector4: SCNVector4(x: 0, y:0, z:1, w: 2*float(M_PI))
I am trying to skew a rectangle so the two vertical sides are slanted but parallel and the top and bottom are horizontal.
I am trying to use CGAffineTransform and have found this code but I am not figuring out what to put in the various parts.
imageView.layer.somethingMagic.imageRightTop = (CGPoint){ 230, 30 };
imageView.layer.somethingMagic.imageRightBottom = (CGPoint){ 300, 150 };
#define CGAffineTransformDistort(t, x, y) (CGAffineTransformConcat(t, CGAffineTransformMake(1, y, x, 1, 0, 0)))
#define CGAffineTransformMakeDistort(x, y) (CGAffineTransformDistort(CGAffineTransformIdentity, x, y))
although this is said to be easy I don't know what to put in the different places.
I assume image view would be my image that I want to change however what goes into somethingMagic. and imageRightTop and imageRightBottom.
Also how do I define t.
If there is a more thorough explanation I would appreciate it since in most cases I found only this as the explanation of what to do to skew a rectangle.
Thanks
Let's assume you have a variable named imageView holding a reference to your UIImageView.
I wrote a little sample to demonstrate how you could get this behavior. What this code does is creating a new CGAffineTransform matrix. This matrix has the same values as the identity transform matrix with one exception: the value at location [2,1]. This value is controlled by the c-parameter of the CGAffineTransformMake-function and controls the shearing along the x-axis. You can change the amount of shearing by setting shearValue.
The code:
Objective-C
CGFloat shearValue = 0.3f; // You can change this to anything you want
CGAffineTransform shearTransform = CGAffineTransformMake(1.f, 0.f, shearValue, 1.f, 0.f, 0.f);
[imageView setTransform:shearTransform];
Swift 5
let shearValue = CGFloat(0.3) // You can change this to anything you want
let shearTransform = CGAffineTransform(a: 1, b: 0, c: shearValue, d: 1, tx: 0, ty: 0)
imageView.transform = shearTransform
And here's what the shearTransform-matrix looks like:
[1 0 0]
[0.3 1 0]
[0 0 1]