FEMeshSmoothingModifier.cpp

/*This file is part of the FEBio Studio source code and is licensed under the MIT license
listed below.

See Copyright-FEBio-Studio.txt for details.

Copyright (c) 2021 University of Utah, The Trustees of Columbia University in
the City of New York, and others.

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#include "stdafx.h"
#include "FEMeshSmoothingModifier.h"
#include <MeshLib/FENodeFaceList.h>
#include <MeshLib/FENodeNodeList.h>
#include <MeshLib/MeshTools.h>
#include "FEFillHole.h"
#include <algorithm>
using namespace std;

//-----------------------------------------------------------------------------
//! Constructor
FEMeshSmoothingModifier::FEMeshSmoothingModifier() : FEModifier("Mesh Smoothing")
{
	m_threshold1 = 0.0;
	m_threshold2 = 0.0;
	m_iteration = 0;
	m_noise = 1.0;
	m_method = 1;
}


//-----------------------------------------------------------------------------
//! Create the decimate mesh. 
//! \todo This implementation will only work with closed surfaces. 

FSMesh* FEMeshSmoothingModifier::Apply(FSMesh* pm)
{
	// make sure this is a triangle mesh
	if (pm->IsType(FE_TRI3) == false) return 0;

	// make a copy of this mesh
	FSMesh* pnew = new FSMesh(*pm);

	//marking the edge nodes.
	vector<int> hashmap; 
	hashmap.reserve(pm->Nodes());
	for (int i = 0 ; i< pm->Nodes();i++)
		hashmap.push_back(0);	
	for (int i =0;i<pm->Edges();++i)
	{
		FSEdge& ed = pm->Edge(i);
		hashmap[ed.n[0]] = -1;
		hashmap[ed.n[1]] = -1;
	}
	switch(m_method)
	{
		case 0:
			Laplacian_Smoothing(pnew,hashmap);
			break;
		case 1:
			Laplacian_Smoothing2(pnew,hashmap);
			break;
		case 2:
			Taubin_Smoothing(pnew,hashmap);
			break;
		case 3:
			Crease_Enhancing_Diffusion(pnew,hashmap);
			break;
		case 4:	
			Add_Noise(pnew,hashmap);
			break;
		default:
			break;
	}

	pnew->RebuildMesh();
	return pnew;
}

void FEMeshSmoothingModifier::Laplacian_Smoothing(FSMesh* pnew,vector<int> hashmap)
{
	//Creating a node node list
	FSNodeNodeList NNL(pnew);

	for(int j =0 ;j<m_iteration;j++)
	{
		for(int i = 0; i < pnew->Nodes() ; i++)
		{
			if(hashmap[i] == 0)
			{
				FSNode& ni = pnew->Node(i);
				vec3d r_new; 
				for (int k = 0; k<NNL.Valence(i);k++)
				{
					vec3d x = pnew->Node(NNL.Node(i, k)).r;
					r_new = r_new + x;
				}
				r_new = r_new/NNL.Valence(i);
				r_new =(r_new * m_threshold1) + (ni.r * (1-m_threshold1));
				ni.r = r_new;
			}
		}
	}
}

void FEMeshSmoothingModifier::Laplacian_Smoothing2(FSMesh* pnew,vector<int> hashmap)
{
	//Creating a node node list
	FSNodeNodeList NNL(pnew);

	for(int j =0 ;j<m_iteration;j++)
	{
		for(int i = 0; i < pnew->Nodes() ; i++)
		{
			if(hashmap[i] == 0)
			{
				FSNode& ni = pnew->Node(i);
				vec3d r_new; 
				double sum_dist=0;
				for (int k = 0; k<NNL.Valence(i);k++)
				{
					vec3d x = pnew->Node(NNL.Node(i, k)).r;
					double dist = (x - ni.r).Length();
					r_new = r_new + (x * dist);
					sum_dist += dist;
				}
				r_new = r_new/sum_dist;
				r_new =(r_new * m_threshold1) + (ni.r * (1-m_threshold1));
				ni.r = r_new;
			}
		}
	}
}

void FEMeshSmoothingModifier::Taubin_Smoothing(FSMesh* pnew,vector<int> hashmap)
{
	//Creating a node node list
	FSNodeNodeList NNL(pnew);
	
	vector<vec3d>phi_node;
	phi_node.reserve(pnew->Nodes());
	for(int j =0 ;j<m_iteration;j++)
	{		
		for(int i = 0; i < pnew->Nodes() ; i++)
		{
			FSNode& ni = pnew->Node(i);
			vec3d r_sum;
			for (int k = 0; k<NNL.Valence(i);k++)
			{
				vec3d x = pnew->Node(NNL.Node(i, k)).r;
				r_sum += x;
			}
			r_sum = r_sum/NNL.Valence(i);
			r_sum -= ni.r;
			phi_node.push_back(r_sum);
		}		
		for(int i = 0; i < pnew->Nodes() ; i++)
		{
			if(hashmap[i] == 0)
			{
				FSNode& ni = pnew->Node(i);
				vec3d phi_old = phi_node[i];

				vec3d r_sq_sum,phi_sq_old; 
				for (int k = 0; k<NNL.Valence(i);k++)
				{
					int neigh_node = NNL.Node(i, k);
					r_sq_sum += phi_node[neigh_node];
				}
				phi_sq_old = r_sq_sum/NNL.Valence(i);
				phi_sq_old -= phi_old;

				ni.r = ni.r - (phi_old * (m_threshold2 - m_threshold1)) - (phi_sq_old *(m_threshold1*m_threshold2));
			}
		}
		phi_node.clear();
	}
}

void FEMeshSmoothingModifier::Crease_Enhancing_Diffusion(FSMesh* pnew,vector<int> hashmap)
{
	//creating Node Element list
	FSNodeFaceList NFL;
	NFL.Build(pnew);

	//calculating m(R) for each face i.e for each triangle	
	vector<FSFace*> mR ;
	vector<vec3d>m_R;
	vector<vec3d>m_R_new;	
	mR.reserve(pnew->Faces());
	m_R.reserve(pnew->Faces());
	m_R_new.reserve(pnew->Faces());

	//for first iteration m_R are normals
	for(int i =0; i< pnew->Faces();i++)
	{
		FSFace& fa = pnew->Face(i);
		m_R.push_back(to_vec3d(fa.m_fn));
	}
	for (int iter = 0 ; iter< m_iteration;iter++)
	{				
		//for each face calculate m_R
		for(int i =0;i<pnew->Faces();i++)
		{
			FSFace& fa = pnew->Face(i);				
			vec3d centroid_R = (pnew->Node(fa.n[0]).r + pnew->Node(fa.n[1]).r + pnew->Node(fa.n[2]).r )/3;
			//finding the neighbouring faces
			for(int j =0 ;j<3 ;j++)
			{
				int nodeID = fa.n[j];
				for (int k = 0; k<NFL.Valence(nodeID);k++)
				{
					FSFace *fa1 = NFL.Face(nodeID,k);
					if(fa1->m_ntag != 1 && fa1->m_elem[0].eid != i)
					{
						fa1->m_ntag = 1;
						mR.push_back(fa1);
					}
				}					
			}
			//now we have the neighbouring faces in mR list
			double weight =0;
			m_R_new.push_back(vec3d(0,0,0));
			for(int k =0;k<mR.size();k++)
			{
				FSFace *fa1 = mR[k];
				vec3d r[3]; //three nodes of the face
				r[0] = pnew->Node(fa1->n[0]).r;
				r[1] = pnew->Node(fa1->n[1]).r;
				r[2] = pnew->Node(fa1->n[2]).r;
				vec3d centroid_S = (r[0]+r[1]+r[2])/3;
				double dist = (centroid_S - centroid_R).Length();
				double angle = acos((fa.m_fn * fa1->m_fn)/(fa.m_fn.Length() * fa1->m_fn.Length()));//angle between the normals
				double weight1 = area_triangle(r) * exp(-m_threshold1 * angle*angle*dist*dist);
				weight += weight1;
				m_R_new[i] += m_R[fa1->m_elem[0].eid] * weight1;
				fa1->m_ntag = 0;
			}
			m_R_new[i] = m_R_new[i]/weight;	
			mR.clear();
		}
		//we have m_R_new for each face.
		for(int i =0 ;i<m_R_new.size();i++)
		{
			m_R[i] = m_R_new[i];
		}
		m_R_new.clear();
		//For each node modify its coodinates
		for(int i = 0 ;i < pnew->Nodes();i++)
		{
			if(hashmap[i] == 0) //not the edge node
			{
				FSNode& ni = pnew->Node(i);
				vec3d vR; 
				double weight=0;
				for (int k = 0; k<NFL.Valence(i);k++)
				{
					FSFace *fa1 = NFL.Face(i,k);
					vec3d r[3]; //three nodes of the face
					r[0] = pnew->Node(fa1->n[0]).r;
					r[1] = pnew->Node(fa1->n[1]).r;
					r[2] = pnew->Node(fa1->n[2]).r;
					vec3d centroid = (r[0]+r[1]+r[2])/3;
					weight += area_triangle(r);
					vec3d PC = centroid - ni.r;
					double temp = PC * m_R[fa1->m_elem[0].eid];
					vR += (m_R[fa1->m_elem[0].eid] * temp)*area_triangle(r);
				}	
				vR = vR/weight;
				ni.r = ni.r + vR;
			}				
		}
	}//end of one iteration
}

double frand(double dmin = 0.0, double dmax = 1.0)
{
	double f = (double)rand() / (double)RAND_MAX;
	return (dmin + f*(dmax - dmin));
}

void FEMeshSmoothingModifier::Add_Noise(FSMesh* pnew, vector<int> hashmap)
{
	for (int j = 0; j<m_iteration; j++)
	{
		for (int i = 0; i < pnew->Nodes(); i++)
		{
			if (hashmap[i] == 0)
			{
				FSNode& ni = pnew->Node(i);
				int temp = 1;
				ni.r.x += frand(-m_noise, m_noise);
				ni.r.y += frand(-m_noise, m_noise);
				ni.r.z += frand(-m_noise, m_noise);
			}
		}
	}
}