float
vsSpline3D::ClosestTimeTo( const vsVector3D& position )
{
//lastBestT is a composite value;
//the whole part is the "before" knot, and the fraction
//is the 't' for that segment.
float lastBestT = 0.5f;
float lastMove = 1.f;
float scale = 0.75f;
vsVector3D lastBestPoint;
vsVector3D lastBestTangent;
int iterations = 0;
while ( lastMove > 0.0001f )
{
lastBestPoint = PositionAtTime(lastBestT);
lastBestTangent = VelocityAtTime(lastBestT);
vsVector3D delta = position - lastBestPoint;
float move = lastBestTangent.Dot(delta) / lastBestTangent.SqLength();
move = vsClamp(move, -lastMove*scale, lastMove*scale);
lastBestT = vsClamp( lastBestT+move, 0.f, 1.f );
lastMove = vsFabs(move);
iterations++;
}
return lastBestT;
}
vsVector3D
vpDrawable::CalculateOptimisedPositionForIndex(int index, int ignoringOptimisedIndex)
{
int preIndex = 0;
int postIndex = m_optimisedIndexCount;
for ( int i = 0; i < m_optimisedIndexCount; i++ )
{
if ( i != ignoringOptimisedIndex )
{
int optIndex = m_optimisedIndex[i];
if ( optIndex <= index )
preIndex = optIndex;
if ( optIndex >= index )
{
postIndex = optIndex;
break;
}
}
}
vsVector3D correctPos = m_samplePos[index];
if ( preIndex == index || postIndex == index )
return correctPos;
// okay. We're on an optimised line segment from preIndex to postIndex; we want to find where
// on that line segment is closest to 'correctPos'.
vsVector3D segmentA = m_samplePos[preIndex];
vsVector3D segmentB = m_samplePos[postIndex];
vsVector3D segmentDirection = segmentB - segmentA;
float segmentLength = segmentDirection.Length();
segmentDirection *= 1.0f / segmentLength;
// Use a dot product to find the projection of 'segmentA->correctPos' onto 'segmentA->segmentB', and use that to pick
// the nearest spot on the line segment.
float projectionLength = segmentDirection.Dot( correctPos - segmentA );
// clamp it into (0..segmentLength).
projectionLength = vsClamp(projectionLength, 0.f, segmentLength);
return (segmentA + (segmentDirection * projectionLength)); // done!
}
