Safety with updating cached geometric quantitie

[CunchengZhu]

When doing topology changes, one needs to consistently maintain the validity of cached geometric quantities such as the corner angles. However, refresh quantities as a whole is expensive. Note that some values in GC are referred to as immediate values which "do not need to be cached".

[CunchengZhu]

Mem3DG/src/init.cpp

Lines 336 to 355 in 8bc7b53

	for (gcs::Corner c : mesh->corners()) {
	// WARNING: Logic duplicated between cached and immediate version
	gcs::Halfedge he = c.halfedge();
	gc::Vector3 pA = vpg->vertexPositions[he.vertex()];
	he = he.next();
	gc::Vector3 pB = vpg->vertexPositions[he.vertex()];
	he = he.next();
	gc::Vector3 pC = vpg->vertexPositions[he.vertex()];
	GC_SAFETY_ASSERT(he.next() == c.halfedge(), "faces must be triangular");
	double q = dot(unit(pB - pA), unit(pC - pA));
	q = clamp(q, -1.0, 1.0);
	double angle = std::acos(q);
	vpg->cornerAngles[c] = angle;
	}
	vpg->refreshQuantities();