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);
}
//
// BaseBrushScript api
//
protected override bool UpdatePositionImpl(
Vector3 translation, Quaternion rotation, float pressure)
{
TrTransform parentXf = TrTransform.TR(translation, rotation);
// Update m_knots
{
Debug.Assert(m_knots.Count > 1, "There should always be at least 2 knots");
PbKnot cur = m_knots[m_knots.Count - 1];
PbKnot prev = m_knots[m_knots.Count - 2];
Vector3 move = parentXf.translation - prev.m_pointer.translation;
cur.m_pointer = parentXf;
float moveLen = move.magnitude;
cur.m_tangentFrame = (moveLen > 1e-5f)
? MathUtils.ComputeMinimalRotationFrame(
move / moveLen, prev.m_tangentFrame, cur.m_pointer.rotation)
: prev.m_tangentFrame;
cur.m_distance = prev.m_distance + moveLen;
cur.m_pressuredSize = PressuredSize(pressure);
}
MaybeCreateChildren();
bool createdControlPoint = false;
for (int i = 0; i < m_children.Count; ++i)
{
PbChild child = m_children[i];
var childXf = child.CalculateChildXfFixedScale(m_knots);
if (child.m_brush.UpdatePosition_LS(childXf, pressure))
{
// Need to save off any control point which is applicable to any of our children.
// This does mean that if we have a giant tree of children, we might be saving
// off every control point.
// TODO: maybe there's a way for the parent to impose some order on this;
// like it doesn't always send positions to its children? But that would make
// interactive drawing less pretty.
createdControlPoint = true;
}
}
if (createdControlPoint)
{
m_knots.Add(m_knots[m_knots.Count - 1].Clone());
}
return(createdControlPoint);
}
// Looks through children to find ones that are attached to a knot.
// Returns the distance to the most recent knot with a child.
// If there are no such children, returns distance to the start of stroke.
protected float DistanceSinceLastKnotBasedChild()
{
PbKnot cur = m_knots[m_knots.Count - 1];
float minDistance = cur.m_distance;
foreach (var child_ in m_children)
{
var child = child_ as PbChildWithOffset;
if (child != null)
{
float distanceFromChildToTip = cur.m_distance - child.GetAttachKnot(m_knots).m_distance;
minDistance = Mathf.Min(minDistance, distanceFromChildToTip);
}
}
return(minDistance);
}
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);
}
