/// <summary>
/// Setup the ratios for each curve of the path. Ratios are based on
/// the speed that that portion of the path must follow. It is complicated
/// by the fact that we must work on the curve via ratios rather than discreet
/// points along it.
/// </summary>
private void InitRatios()
{
int nFrames;
// for each curve along the path
for (int i = 0; i < lengthRatios.Count; i++)
{
try
{
// this curve amounts to what % of the total path length
double lengthPortion = (double)(lengthRatios[i].length / (double)pathLength);
// based on total path time, how much time should be spent traversing this curve
double timePortion = (lengthPortion * traversalTime);
// how fast must sprite travel on this curve based on time spent on it.
// Remember, this gets re-considered as a ratio later so the speed really
// won't be different for this curve than others.
double thisSpeed = lengthRatios[i].length / timePortion;
// determine how far to travel per frame
double frameSpeed = thisSpeed / SpriteManager.FPS;
// determine how many frames will show while travelling this curve
nFrames = (int)Math.Round(lengthRatios[i].length / frameSpeed);
// at least show one frame in this curve, no matter what
nFrames = nFrames < 1? 1: nFrames;
// determine the ratio for the curve based on the number of frames to show
double ratio = (double)(1.0d / (double)nFrames);
// store what we calculated
LengthRatio lrRef = lengthRatios[i];
lrRef.length = lengthRatios[i].length;
lrRef.ratio = ratio;
lengthRatios[i] = lrRef;
}
catch (Exception e)
{
throw e;
}
}
ratioStep = lengthRatios[0].ratio;
}
/// <summary>
/// Determine and store the length of each curve segment along the whole path
///
/// Assumption:
/// points has 3*n+1 points in it.
///
/// </summary>
private void FillInSegmentLengths()
{
if (lengthRatios == null)
{
throw new Exception("lengthRatios must be defined assigned before calling FillInEndTangents");
}
pathLength = 0;
for (int i = 0; i < segmentCount; i++)
{
LengthRatio lr = new LengthRatio();
lr.length =
BezierSprite.CalculateCurveLength(
points.GetRange(i * 3, 4).ToArray() // there are 4 points to each segment. * 3 because we start each next segment with the end point of the previous segment
);
lr.ratio = defaultRatio; // default value since we haven't calc'd ratios yet
lengthRatios[i] = lr;
pathLength += lr.length; // calc length of whole path
}
}
/// <summary>
/// Determine and store the length of each curve segment along the whole path
///
/// Assumption:
/// points has 3*n+1 points in it.
///
/// </summary>
private void FillInSegmentLengths()
{
if (lengthRatios == null) throw new Exception("lengthRatios must be defined assigned before calling FillInEndTangents");
pathLength = 0;
for (int i = 0; i < segmentCount; i++)
{
LengthRatio lr = new LengthRatio();
lr.length =
BezierSprite.CalculateCurveLength(
points.GetRange(i * 3, 4).ToArray() // there are 4 points to each segment. * 3 because we start each next segment with the end point of the previous segment
);
lr.ratio = defaultRatio; // default value since we haven't calc'd ratios yet
lengthRatios[i] = lr;
pathLength += lr.length; // calc length of whole path
}
}
/// <summary>
/// If the ratio is 0.0d we calculate tangents based on the end points to their
/// nearest guide point. This does that.
/// </summary>
private void FillInEndTangents()
{
if (lengthRatios == null)
{
throw new Exception("lengthRatios must be defined assigned before calling FillInEndTangents");
}
for (int i = 0; i < segmentCount; i++)
{
LengthRatio lr = lengthRatios[i];
Point pt;
// we can't determine angles if guide points are exactly the same as node points.
// Therefore, if that is the case, find another guide point to use.
// if first guide point is not same as first node
if (points[i * 3] != points[i * 3 + 1])
{
pt = points[i * 3 + 1];
}
else // else if 2nd guide point is not same as first node
if (points[i * 3] != points[i * 3 + 2])
{
pt = points[i * 3 + 2];
}
else // else if end point is not same as first node
if (points[i * 3] != points[i * 3 + 3])
{
pt = points[i * 3 + 3];
}
else // else all points in curve are the same - just accept it and move on
{
pt = points[i * 3];
}
if (pt == points[i * 3]) // all points in curve are same, set tangent to 0 degrees
{
lr.startTangent = 0.0d;
lr.endTangent = 0.0d;
continue;
}
else
{
lr.startTangent = CalculateAngleBetweenPoints(points[i * 3], pt);
}
// if 2nd guide point is not same as 2nd node
if (points[i * 3 + 3] != points[i * 3 + 2])
{
pt = points[i * 3 + 2];
}
else // else if 1st guide point is not same as 2nd node
if (points[i * 3 + 3] != points[i * 3 + 1])
{
pt = points[i * 3 + 1];
}
else // else if 1st node is not same as 2nd node
if (points[i * 3 + 3] != points[i * 3 + 0])
{
pt = points[i * 3 + 0];
}
lr.endTangent = CalculateAngleBetweenPoints(pt, points[i * 3 + 3]);
lengthRatios[i] = lr;
}
}
