// Hit testing between this thing and a single segment. If hit, the center point on
// the segment being hit is returned, along with the spot on the line from 0 to 1 if
// a line segment was hit.
public bool Hit(Segment seg, ref Point ptHitCenter, ref double lineHitLocation)
{
double minDxSquared = size + seg.radius;
minDxSquared *= minDxSquared;
// See if falling thing hit this body segment
if (seg.IsCircle())
{
if (SquaredDistance(center.X, center.Y, seg.x1, seg.y1) <= minDxSquared)
{
ptHitCenter.X = seg.x1;
ptHitCenter.Y = seg.y1;
lineHitLocation = 0;
return true;
}
}
else
{
double sqrLineSize = SquaredDistance(seg.x1, seg.y1, seg.x2, seg.y2);
if (sqrLineSize < 0.5) // if less than 1/2 pixel apart, just check dx to an endpoint
{
return (SquaredDistance(center.X, center.Y, seg.x1, seg.y1) < minDxSquared) ? true : false;
}
else
{ // Find dx from center to line
double u = ((center.X - seg.x1) * (seg.x2 - seg.x1) + (center.Y - seg.y1) * (seg.y2 - seg.y1)) / sqrLineSize;
if ((u >= 0) && (u <= 1.0))
{ // Tangent within line endpoints, see if we're close enough
double xIntersect = seg.x1 + (seg.x2 - seg.x1) * u;
double yIntersect = seg.y1 + (seg.y2 - seg.y1) * u;
if (SquaredDistance(center.X, center.Y,
xIntersect, yIntersect) < minDxSquared)
{
lineHitLocation = u;
ptHitCenter.X = xIntersect;
ptHitCenter.Y = yIntersect; ;
return true;
}
}
else
{
// See how close we are to an endpoint
if (u < 0)
{
if (SquaredDistance(center.X, center.Y, seg.x1, seg.y1) < minDxSquared)
{
lineHitLocation = 0;
ptHitCenter.X = seg.x1;
ptHitCenter.Y = seg.y1;
return true;
}
}
else
{
if (SquaredDistance(center.X, center.Y, seg.x2, seg.y2) < minDxSquared)
{
lineHitLocation = 1;
ptHitCenter.X = seg.x2;
ptHitCenter.Y = seg.y2;
return true;
}
}
}
}
return false;
}
return false;
}
// Update the segment's position and compute a smoothed velocity for the circle or the
// endpoints of the segment based on the time it took it to move from the last position
// to the current one. The velocity is in pixels per second.
public void UpdateSegment(Segment s)
{
segLast = seg;
seg = s;
DateTime cur = DateTime.Now;
double fMs = cur.Subtract(timeLastUpdated).TotalMilliseconds;
if (fMs < 10.0)
fMs = 10.0;
double fFPS = 1000.0 / fMs;
timeLastUpdated = cur;
if (seg.IsCircle())
{
xVel = xVel * smoothing + (1.0 - smoothing) * (seg.x1 - segLast.x1) * fFPS;
yVel = yVel * smoothing + (1.0 - smoothing) * (seg.y1 - segLast.y1) * fFPS;
}
else
{
xVel = xVel * smoothing + (1.0 - smoothing) * (seg.x1 - segLast.x1) * fFPS;
yVel = yVel * smoothing + (1.0 - smoothing) * (seg.y1 - segLast.y1) * fFPS;
xVel2 = xVel2 * smoothing + (1.0 - smoothing) * (seg.x2 - segLast.x2) * fFPS;
yVel2 = yVel2 * smoothing + (1.0 - smoothing) * (seg.y2 - segLast.y2) * fFPS;
}
}