/////////////////////////////////////////////////////////////////////////////
//
// javascript source code for the ski/snowboard calculator at:
// http://www.natew.com/frames.cgi/software/html.SnowboardCalculator
//
// I'd put a copyright notice here:
//
// Xxxxxxxxx (c) 2001 Xxxx Xxxxxxxx.  Xxx xxxxxx xxxxxxxx.
//
// But that would be silly.  The key concepts here are not mine - if
// anyone deserves copyright on this it's Pythagoras, and he's dead.
//
// Nate Waddoups, 14 April 2001
//
/////////////////////////////////////////////////////////////////////////////

var rPi = 3.1415926535;

function SolveForRadius(form)
{
  var rDepth = form.elements["Depth"].value / 1000;
  var rEdgeLength = form.elements["EdgeLength"].value / 100;

  rRadius = ((rEdgeLength * rEdgeLength) / (8 * rDepth));
  
  form.elements["Radius"].value = rRadius;

  SolveForCarve (form);
}

function SolveForDepth(form)
{
  var rRadius = form.elements["Radius"].value;
  var rHalfEdge = (form.elements["EdgeLength"].value / 100) / 2;

  rDepth = rRadius - Math.sqrt ((rRadius * rRadius) - (rHalfEdge * rHalfEdge));

  rDepth *= 1000;

  form.elements["Depth"].value = 
      Math.round (rDepth * 100) / 100;

  SolveForCarve (form);
}

function SolveForEdgeLength(form)
{
  var rRadius = form.elements["Radius"].value;
  var rDepth = form.elements["Depth"].value / 1000;

  rEdgeLength = sqrt (rRadius * 8 * rDepth);

  form.elements["EdgeLength"].value = rEdgeLength;

  SolveForCarve (form);
}

function SolveForCarve (form)
{
  var rRadius = form.elements["Radius"].value;
  var rDepth = form.elements["Depth"].value / 1000;
  var rEdgeLength = form.elements["EdgeLength"].value / 100;
  var rEdgeAngle = form.elements["EdgeAngle"].value * rPi / 180;

  var rDecamber =  rDepth * Math.tan (rEdgeAngle);

  document.all["Decamber"].innerHTML = 
      Math.round (rDecamber * 100000) / 100;

  var rCarveDepth = rDepth / Math.cos (rEdgeAngle);

  document.all["EffectiveDepth"].innerHTML = 
      Math.round (rCarveDepth * 100000) / 100;

  var rCarveRadius = ((rEdgeLength * rEdgeLength) / (8 * rCarveDepth));
  //
  //  rCarveRadius = rRadius * Math.cos (rEdgeAngle);
  //
  // same results either way!

  document.all["CarveRadius"].innerHTML = 
      Math.round (rCarveRadius * 100) / 100;

  var rSpeed = Math.sqrt (Math.sin (rEdgeAngle) * rRadius * 9.81);

  document.all["Speed"].innerHTML = 
      Math.round (rSpeed * 100) / 100;

  var rCentForce = ((rSpeed * rSpeed) / rCarveRadius) / 9.81;

  document.all["CentForce"].innerHTML = 
      Math.round (rCentForce * 100) / 100;

  var rTotalForce = Math.sqrt ((rCentForce * rCentForce) + 1);

  document.all["TotalForce"].innerHTML =
      Math.round (rTotalForce * 100) / 100;

}

function ChangeWidth (form)
{
  var rTipWidth = form.elements["TipWidth"].value;
  var rWaistWidth = form.elements["WaistWidth"].value;
  var rTailWidth = form.elements["TailWidth"].value;

  var rWaistWidthNoSidecut = (rTipWidth / 2) + (rTailWidth / 2);
  var rDepth = (0 + rWaistWidthNoSidecut - rWaistWidth) / 2;

  form.elements["Depth"].value =
        (Math.round (rDepth * 1000)) / 100;

  var rTaperMillimeters = (rTipWidth - rTailWidth) * 10;
  form.elements["TaperMillimeters"].value =
	(Math.round (rTaperMillimeters * 100)) / 100;  

  SolveForRadius (form);
  SolveForTaperDegrees (form);
  SolveForTaperSetback (form);
}

function SolveForTaperMillimeters (form)
{
  var rEdgeLength = form.elements["EdgeLength"].value;
  var rTaperDegrees = form.elements["TaperDegrees"].value;
  var rTaperRadians = rTaperDegrees * rPi / 180;  
  
  var rTaperMillimeters = Math.sin (rTaperRadians) * rEdgeLength;

  form.elements["TaperMillimeters"].value =
	(Math.round (rTaperMillimeters * 100)) / 100;

  SolveForTaperSetback (form);
}

function SolveForTaperDegrees (form)
{
  var rEdgeLength = form.elements["EdgeLength"].value;
  var rTaperMillimeters = form.elements["TaperMillimeters"].value;

  var rTaperRadians = Math.asin (rTaperMillimeters / rEdgeLength);
  var rTaperDegrees = rTaperRadians * 180 / rPi;
  
  form.elements["TaperDegrees"].value = 
	(Math.round (rTaperDegrees * 100)) / 100;

  SolveForTaperSetback (form);
}

function SolveForTaperSetback (form)
{
  var rRadius = form.elements["Radius"].value;
  var rTaperDegrees = form.elements["TaperDegrees"].value;
  var rTaperRadians = rTaperDegrees * rPi / 180;  

  var rSetback = Math.sin (rTaperRadians) * (rRadius * 1000);

  form.elements["Setback"].value = 
	(Math.round (rSetback) * 10) / 1000;
}

function SolveForTaper (form)
{
  var rSetback = form.elements["Setback"].value;
  var rRadius = form.elements["Radius"].value;

  var rTaperDegrees = 0;	

  SolveForTaperMillimeters (form);
}

/////////////////////////////////////////////////////////////////////////////
// EOF.  Stop reading here ->