protected override TrTransform CalculateChildXf(List <PbKnot> parentKnots)
{
TrTransform actionInCanvasSpace;
{
PbKnot knot = GetAttachKnot(parentKnots);
float rotationDegrees = knot.m_distance * App.UNITS_TO_METERS * m_twist;
TrTransform offset = m_offset;
// It's cleaner to tack a TrTransform.S(size) onto the action, but that
// would modify .scale, which is currently interpreted as "pointer size"
// (affecting control point density) and which is also assumed by most
// brushes to be constant.
if (m_pressureAffectsOffset)
{
offset.translation *= knot.m_pressuredSize;
}
else
{
offset.translation *= m_brush.BaseSize_LS;
}
TrTransform action =
TrTransform.R(Quaternion.AngleAxis(rotationDegrees, Vector3.forward))
* offset;
actionInCanvasSpace = action.TransformBy(knot.GetFrame(m_frame));
}
var cur = parentKnots[parentKnots.Count - 1];
return(actionInCanvasSpace * cur.m_pointer);
}
protected override TrTransform CalculateChildXf(List <PbKnot> parentKnots)
{
PbKnot lastKnot = parentKnots[parentKnots.Count - 1];
float distanceMeters = lastKnot.m_distance * App.UNITS_TO_METERS;
float t = O.CyclesPerMeter * distanceMeters + (float)m_strand / O.NumStrands;
// Our periodic function makes the plait look pretty square; maybe add
// some rotation to break things up a bit?
float rotations = (O.CyclesPerMeter * distanceMeters) * O.RotationsPerCycle;
float amplitude = lastKnot.m_pressuredSize / 2; // /2 because size is diameter, not radius.
TrTransform action =
TrTransform.R(rotations * 360, Vector3.forward) *
TrTransform.T(SomePeriodicFunction(t) * amplitude);
TrTransform actionInCanvasSpace = action.TransformBy(lastKnot.GetFrame(AttachFrame.LineTangent));
return(actionInCanvasSpace * lastKnot.m_pointer);
}