A Moving Platform

• Sorry the art on this is bad.
• I am going to build a moving platform.
  • It will start at a starting location.
  • When triggered, it will move to a ending location.
  • Next time triggered, it will return to the starting location.
• I want to start with an actor blueprint called BP_Platform
  • Add a single component of type cube.
  • Change the scale to be < 3, 0.1, 0.25>
    • You could expose the 3 to the outside world as PlatformLength.
    • I made the materials a BasicAsset01, but you could add texture and make it match the game.
    • 
    • I added vector variables StartLocation and EndLocation. and exposed these to the outside world.
    • 
  • I want to have this platform move.
    • To do this, I will need a state variable.
    • This will keep track of it's location.
    • I could easily change this to do more, we will discuss this later.
    • But for now, I just made an int.
      • If it is at the start location, the state is 0.
      • If it is at the end location, the state is 1.
    • Finally I added a bool indicating if it is in motion or not.
  • I initialized these in the construction script

    • PlatformT::PlatformT {
          isInMotion = false;
          state = 0
          location= StartLocation
      } 

    • 
  • I want to be able to control the state variable so I build a SetState function

    • PlatformT::SetState{
          if Location == startLocation {
             state = 0
          } else {
             state = 1
          }
      } 

    • 
  • I want to create an event that starts the platform in motion
    • The heart of this action is a Timeline Node
    • Timelines will automatically generate a series of values over a set period of time.
    • Start by creating a custom event StartMotion.
    • I don't want the thing to run if it is already running so

      • PlatformT::StartMotion {
           if (not isInMotion) {
               // make sure the current state is accurate
               SetState() 
               isInMotion = true;
               // more to be added.
               StartTimeline     
           }
        } 

      • 
    • I now need to create the timeline.
      • This can only be done in the EventGraph portion of the class.
      • Add a timeline node.
        • Double click on this
        • Set the length to be 5 seconds
        • add a new float track.
        • Add 0,0 as a start point
        • Add 5,1 as an end point.
      • We will use a switch to control the input.
      • If we are in state 1, play from start.
      • If we are in state 2, Reverse from end.
      • The picture picks up from the set at the end of the last picture.
      • 
    • A LERP node is a natural companion to the timeline.
      • This stands for linear interpolation.
      • $ f(\alpha) = A(1-\alpha) + B\alpha$
      • This is a wonderful thing.
      • The $\alpha$ is the number supplied by the timeline.
      • A is the start vector location
      • B is the end vector location
      • The output is the average of the two.
      • 
• Add one of these platforms to the world
  • Don't forget to set start location (2000,0,180)
  • And the end location (3000,0,180)
  • Add a keypres in the player to test this.
  • 
  • I added a event to the platform to start it moving as well.
  • 
• You could do many more things
  • Add a button that starts a particular platform moving
  • Have all platforms in motion from the start.
  • You name it!
  • Have them start at random times.