// After we split an edge, we have created a new edge and a new vertex.
// The edge needs to inherit the constraint on the other pre-existing edge that we kept.
// In addition, if the edge vertices were both constrained, then we /might/
// want to also constrain this new vertex, possibly project to constraint target.
void update_after_split(int edgeID, int va, int vb, DMesh3.EdgeSplitInfo splitInfo)
{
bool bPositionFixed = false;
if (constraints != null && constraints.HasEdgeConstraint(edgeID))
{
// inherit edge constraint
constraints.SetOrUpdateEdgeConstraint(splitInfo.eNewBN, constraints.GetEdgeConstraint(edgeID));
// [RMS] update vertex constraints. Note that there is some ambiguity here.
// Both verts being constrained doesn't inherently mean that the edge is on
// a constraint, that's why these checks are only applied if edge is constrained.
// But constrained edge doesn't necessarily mean we want to inherit vert constraints!!
//
// although, pretty safe to assume that we would at least disable flips
// if both vertices are constrained to same line/curve. So, maybe this makes sense...
//
// (perhaps edge constraint should be explicitly tagged to resolve this ambiguity??)
// vert inherits Fixed if both orig edge verts Fixed, and both tagged with same SetID
VertexConstraint ca = constraints.GetVertexConstraint(va);
VertexConstraint cb = constraints.GetVertexConstraint(vb);
if (ca.Fixed && cb.Fixed)
{
int nSetID = (ca.FixedSetID > 0 && ca.FixedSetID == cb.FixedSetID) ?
ca.FixedSetID : VertexConstraint.InvalidSetID;
constraints.SetOrUpdateVertexConstraint(splitInfo.vNew,
new VertexConstraint(true, nSetID));
bPositionFixed = true;
}
// vert inherits Target if both source verts and edge have same Target
if (ca.Target != null && ca.Target == cb.Target &&
constraints.GetEdgeConstraint(edgeID).Target == ca.Target)
{
constraints.SetOrUpdateVertexConstraint(splitInfo.vNew,
new VertexConstraint(ca.Target));
project_vertex(splitInfo.vNew, ca.Target);
bPositionFixed = true;
}
}
if (EnableInlineProjection && bPositionFixed == false && target != null)
{
project_vertex(splitInfo.vNew, target);
}
}
// resolve vertex constraints for collapsing edge eid=[a,b]. Generally we would
// collapse a to b, and set the new position as 0.5*(v_a+v_b). However if a *or* b
// are constrained, then we want to keep that vertex and collapse to its position.
// This vertex (a or b) will be returned in collapse_to, which is -1 otherwise.
// If a *and* b are constrained, then things are complicated (and documented below).
protected bool can_collapse_vtx(int eid, int a, int b, out int collapse_to)
{
collapse_to = -1;
if (constraints == null)
{
return(true);
}
VertexConstraint ca = constraints.GetVertexConstraint(a);
VertexConstraint cb = constraints.GetVertexConstraint(b);
// no constraint at all
if (ca.Fixed == false && cb.Fixed == false && ca.Target == null && cb.Target == null)
{
return(true);
}
// handle a or b fixed
if (ca.Fixed == true && cb.Fixed == false)
{
collapse_to = a;
return(true);
}
if (cb.Fixed == true && ca.Fixed == false)
{
collapse_to = b;
return(true);
}
// if both fixed, and options allow, treat this edge as unconstrained (eg collapse to midpoint)
// [RMS] tried picking a or b here, but something weird happens, where
// eg cylinder cap will entirely erode away. Somehow edge lengths stay below threshold??
if (AllowCollapseFixedVertsWithSameSetID &&
ca.FixedSetID >= 0 &&
ca.FixedSetID == cb.FixedSetID)
{
return(true);
}
// handle a or b w/ target
if (ca.Target != null && cb.Target == null)
{
collapse_to = a;
return(true);
}
if (cb.Target != null && ca.Target == null)
{
collapse_to = b;
return(true);
}
// if both vertices are on the same target, and the edge is on that target,
// then we can collapse to either and use the midpoint (which will be projected
// to the target). *However*, if the edge is not on the same target, then we
// cannot collapse because we would be changing the constraint topology!
if (cb.Target != null && ca.Target != null && ca.Target == cb.Target)
{
if (constraints.GetEdgeConstraint(eid).Target == ca.Target)
{
return(true);
}
}
return(false);
}