I'm writing my first scenekit project and i'm trying use Pan gesture to rotate a simple object in my scene (object is a simple L cube shape imported from .dae file, pivot point is set correctly).
I went through multiple SO solutions and tutorials and i've put together some code, but the rotation is not working correctly. If i repeatedly try to rotate the object along one axis, it works correctly, but when i try the other direction, at the start of the pan the object resets to it's initial position. Sometimes the rotation randomly quirks or jumps as well. I'm not sure if i used the correct approach to this, please advise.. Here's my code:
func handlePan(sender: UIPanGestureRecognizer){
// determine pan direction
let velocity: CGPoint = sender.velocity(in: sender.view!)
if self.panDirection == nil {
if velocity.x > 0 && velocity.x > abs(velocity.y) { self.panDirection = "right" }
if velocity.x < 0 && abs(velocity.x) > abs(velocity.y) { self.panDirection = "left" }
if velocity.y < 0 && abs(velocity.y) > abs(velocity.x) { self.panDirection = "up" }
if velocity.y > 0 && velocity.y > abs(velocity.x) { self.panDirection = "down" }
}
// do rotation only on selected SCNNode
if self.selectedBrickNode != nil {
// start of pan gesture
if sender.state == UIGestureRecognizerState.began{
// remember initial rotation angle
self.initRot = self.selectedBrickNode.rotation.w
}
let translation = sender.translation(in: sender.view!)
let pan_x = Float(translation.x)
let pan_y = Float(-translation.y)
// add rotation angle to initial rotation
var anglePan = self.initRot + (Float)(sqrt(pow(pan_x,2)+pow(pan_y,2)))*(Float)(Double.pi)/180.0
var rotVector = SCNVector4()
// if left/right, rotate on Y axis
rotVector.x = (self.panDirection == "left" || self.panDirection == "right" ) ? 0 : -pan_y
// if up/down, rotate on X axis
rotVector.y = (self.panDirection == "up" || self.panDirection == "down" ) ? 0 : pan_x
rotVector.z = 0
rotVector.w = anglePan
// set SCNNode's rotation
self.selectedBrickNode.rotation = rotVector
// end of pan gesture
if(sender.state == UIGestureRecognizerState.ended) {
// reset initial rotation
self.initRot = 0.0
// calculate degrees so we can snap to 90deg increments
var angle = anglePan * (Float) (180.0 / Double.pi)
// snap to 90deg increments
let diff = angle.truncatingRemainder(dividingBy: 90.0)
if diff <= 45 {
angle = angle - diff
}else{
angle = (angle - diff ) + 90
}
// set new rotation to snap
rotVector.w = angle * (Float)(Double.pi)/180.0
self.selectedBrickNode.rotation = rotVector
self.selectedBrickNode = nil
}
}
}
After a LOT of research and few hours of head-banging the wall, i finally found a working solution.
My working code:
func handlePan(sender: UIPanGestureRecognizer){
// get pan direction
let velocity: CGPoint = sender.velocity(in: sender.view!)
if self.panDirection == nil {
self.panDirection = GameHelper.getPanDirection(velocity: velocity)
}
// if selected brick
if self.selectedBrickNode != nil {
if sender.state == UIGestureRecognizerState.began{
lastAngle = 0.0 // reset last angle
}
let translation = sender.translation(in: sender.view!)
let anglePan = (self.panDirection == "horizontal") ? GameHelper.deg2rad(deg: Float(translation.x)) : GameHelper.deg2rad(deg: Float(translation.y))
let x:Float = (self.panDirection == "vertical" ) ? 1 : 0.0
let y:Float = (self.panDirection == "horizontal" ) ? 1 : 0.0
// calculate the angle change from last call
let fraction = anglePan - lastAngle
lastAngle = anglePan
// perform rotation by difference to last angle
selectedBrickNode.transform = SCNMatrix4Mult(selectedBrickNode.transform,SCNMatrix4MakeRotation(fraction, x, y, 0.0))
if(sender.state == UIGestureRecognizerState.ended) {
// calculate angle to snap to 90 degree increments
let finalRotation = GameHelper.rad2deg(rad:anglePan)
let diff = finalRotation.truncatingRemainder(dividingBy: 90.0)
var finalDiff = Float(0.0)
switch diff {
case 45..<90 :
finalDiff = 90 - diff
case 0..<45 :
finalDiff = -diff
case -45..<0 :
finalDiff = abs(diff)
case -90 ..< -45 :
finalDiff = -90 - diff
default:
print("do nothing")
}
// final transform to apply snap to closest 90deg increment
let snapAngle = GameHelper.deg2rad(deg: finalDiff)
selectedBrickNode.transform = SCNMatrix4Mult(selectedBrickNode.transform, SCNMatrix4MakeRotation(snapAngle, x, y, 0.0))
// remove highlight from node and deselect
self.selectedBrickNode?.geometry?.materials = [hlp.defaultMaterial]
self.selectedBrickNode = nil
}
}
}
and GameHelper.swift
class GameHelper {
static func rad2deg( rad:Float ) -> Float {
return rad * (Float) (180.0 / Double.pi)
}
static func deg2rad( deg:Float ) -> Float{
return deg * (Float)(Double.pi / 180)
}
static func getPanDirection(velocity: CGPoint) -> String {
var panDirection:String = ""
if ( velocity.x > 0 && velocity.x > abs(velocity.y) || velocity.x < 0 && abs(velocity.x) > abs(velocity.y) ){
panDirection = "horizontal"
}
if ( velocity.y < 0 && abs(velocity.y) > abs(velocity.x) || velocity.y > 0 && velocity.y > abs(velocity.x)) {
panDirection = "vertical"
}
return panDirection
}
}