Tukukkk

I need to draw a line between two spritnodes while hand is pointing from one node to another with rendering or animation.
The line drawing is working for me as I follow this link Bobjt's answer, Animate Path Drawing in SpriteKit . I have used concept of fragment shader and vertex shader here..

I have added animatestroke.fsh file and apply the following code .. But the handplayer animation and line drawing speed is mismatching some times.
my line rendering i have given increment by

strokeLengthFloat += 0.01

And handplayer duration is 1.5:

let moveTosecondObject = SKAction.move(to: handmovepoint, duration: 1.5 )

Here is my implementation code:

variable declaration

var handplayer = SKSpriteNode()

var firstObject = SKSpriteNode()

var secondObject = SKSpriteNode()

var startTrigger: Bool = false



let strokeSizeFactor = CGFloat( 2.0 )

var strokeShader: SKShader!

var strokeLengthUniform: SKUniform!

var _strokeLengthFloat: Float = 0.0

var strokeLengthKey: String!

var strokeLengthFloat: Float {

    get {

        return _strokeLengthFloat

    }

    set( newStrokeLengthFloat ) {

        _strokeLengthFloat = newStrokeLengthFloat

        strokeLengthUniform.floatValue = newStrokeLengthFloat

    }

}

Loading method

   override func didMove(to view: SKView) {

   handplayer = SKSpriteNode(imageNamed: "HandImage.png")

    handplayer.size.width = handplayer.size.width * 0.5

    handplayer.size.height = handplayer.size.height * 0.5

    handplayer.position.x =  firstObject.position 

    self.addChild(handplayer)

    UpdatePosition()

   }



    func UpdatePosition(){





       //Line drawing part

          strokeLengthKey = "u_current_percentage"

          strokeLengthUniform = SKUniform( name: strokeLengthKey, float: 0.0 )

          let uniforms: [SKUniform] = [strokeLengthUniform]

          strokeShader = shaderWithFilename( "animateStroke", fileExtension: "fsh", uniforms: uniforms )

    strokeLengthFloat = 0.0



           let cameraNode = SKCameraNode()

           self.camera = cameraNode



          let lineStartPosition = CGPoint(x:firstObject.frame.origin.x+firstObject.size.width/2,y:firstObject.frame.origin.y-firstObject.size.height*0.2)



           let lineEndPosition = CGPoint(x:secondObject.frame.origin.x+secondObject.size.width/2,y:secondObject.frame.origin.y+secondObject.size.height*1.2)



         let path = CGMutablePath()

         path.move(to: CGPoint(x:  lineStartPosition.x, y:  lineStartPosition.y))

         path.addLine(to: CGPoint(x: : lineEndPosition.x, y:  lineEndPosition.y), transform: CGAffineTransform.identity)



         let strokeWidth = 1.0 * strokeSizeFactor

         let shapeNode = SKShapeNode( path: path )

         shapeNode.lineWidth = strokeWidth

         shapeNode.lineCap = .square

         shapeNode.addChild( cameraNode )

         shapeNode.strokeShader = strokeShader

         shapeNode.calculateAccumulatedFrame()

         self.addChild( shapeNode )





    }



     // center the camera

     cameraNode.position = CGPoint( x: self.frame.size.width/2.0, y: self.frame.size.height/2.0 )





     **Handplayer Rendering part**

       let handmovepoint = CGPoint(x: secondObject.position.x , y: secondObject.position.y + handplayer.size.height*0.1 )



       let moveTosecondObject = SKAction.move(to:  handmovepoint, duration:  1.5 )

    let delay = SKAction.wait(forDuration: 1)

    handplayer.run(SKAction.sequence([ delay ]), completion: {() -> Void in

        self.startTrigger = true



        self.handplayer.run(SKAction.sequence([ moveTosecondObject ]), completion: {() -> Void in

            //self.handplayer.alpha = 0.0





       })



 }

    //line rendering part

    override func update(_ currentTime: TimeInterval) {



    if(startTrigger){



        strokeLengthFloat +=   0.01 



    }



    if startTrigger == true{



        if strokeLengthFloat > 1.0 {

           //once line drawing completed 

             self.startTrigger = false



            print("Line drawing ended")

            self.handplayer.alpha = 0.0

            self.handplayer.removeFromParent()





            }



           }

         }

animatestroke.fsh class

        void main()

       {

       if ( u_path_length == 0.0 ) {

              gl_FragColor = vec4( 0.0, 0.0, 1.0, 1.0 ); // draw blue // this is an error

        } else if ( v_path_distance / u_path_length <= u_current_percentage ) {

              gl_FragColor = vec4( 1.0, 0.0, 0.0, 1.0 ); // draw red

        } else {

              gl_FragColor = vec4( 0.0, 0.0, 0.0, 0.0 ); // draw nothing

        }

  }

How could i fix this: Or If Anyone have other idea for implementhing this scenario share your Idea.. Any help will be appreciated..