A Virtual Stringed Instrument With Haptic Feedback

Progress Report - 4/7/03

Jeff Feasel

See the results here.

Demos

• Here's a demo for the string sound synthesis part.  Use the keyboard (0-9 keys) to trigger the string.  (Needs DirectX and OpenGL libs)
  
• If you want a demo for the haptic string portion (i.e. plucking a string with the phantom) come see me and I'll be glad to show it off.
• Right now I'm working on getting the two parts to work together.  Stay tuned.
  

String Sound Synth Model - Current State

• Only 1 string for now.
  
• Using very simple Karplus-Strong waveguide.
• Models decay crudely.  Should be frequency-dependent.
• No dispersion.
  
• Random excitation shape.  Only amplitude comes from haptic model.
• Can not mute the string once it has started.

String Sound Synth - To Do

• More advanced waveguide model.  Dispersion, freq-dependent damping.
  
• Take excitation shape from the haptic model.

String Haptic Model - Current State

• Uses the PHANToM (hooray!)
  
• Force modelled like a spring
  
• Magnitude is proportional to transversal displacement only (side-to-side, not up-and-down)
• Applied in the direction of displacement.
• Kind of a hack based on what "felt" right.
• Constants have no physical basis, yet.
  
• When does the string slide off the pick?
• When a maximum displacement is reached.
• A linear function of penetration depth.
• String length chosen using keyboard.
  

String Haptic Model - To Do

• Model the pick-string contact physically.
• Factors:   Friction, incident angle.
• Decide lateral force along the pick should deicde when it will release.
  
• Figure out how to handle fretting.
  
• Superimposed fretboard might be too much.
  
• Maybe just fret with the keyboard?
• A nicer UI.  Not needed (you can play "by feel") but it helps to get your bearings.