HoneycombVertexMeshGenerator.cpp

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*/
 
#include "HoneycombVertexMeshGenerator.hpp"
#include <boost/make_shared.hpp>
#include <boost/shared_ptr.hpp>
 
HoneycombVertexMeshGenerator::HoneycombVertexMeshGenerator(unsigned numElementsAcross,
                                                           unsigned numElementsUp,
                                                           bool isFlatBottom,
                                                           double cellRearrangementThreshold,
                                                           double t2Threshold,
                                                           double elementArea)
{
    assert(numElementsAcross > 0);
    assert(numElementsUp > 0);
    assert(cellRearrangementThreshold > 0.0);
    assert(t2Threshold > 0.0);
    assert(elementArea > 0.0);
 
    std::vector<Node<2>*> nodes;
    std::vector<VertexElement<2,2>*>  elements;
 
    unsigned node_index = 0;
    unsigned node_indices[6];
    unsigned element_index;
 
    /*
     * Create the nodes, row by row, from the bottom up. On the first row we
     * have numElementsAcross nodes, all of which are boundary nodes. This row
     * only exists if isFlatBottom is false.
     */
    if (!isFlatBottom)
    {
        for (unsigned i = 0; i < numElementsAcross; i++)
        {
            Node<2>* p_node = new Node<2>(node_index, true, i + 0.5, 0);
            nodes.push_back(p_node);
            node_index++;
        }
    }
    /*
     * On each interior row, and the first row if isFlatBottom is true, we have
     * numElementsAcross+1 nodes. On the penultimate row, all nodes are boundary
     * nodes. The same is true for the second row, if isFlatBottom is false. On
     * other rows, the first and last nodes only are boundary nodes.
     */
    for (unsigned j = 1; j < 2*numElementsUp + 1; j++)
    {
        if ((j == 1) && isFlatBottom)
        {
            for (unsigned i = 0; i <= numElementsAcross; i++)
            {
                double x_coord = ((j%4 == 0)||(j%4 == 3)) ? i + 0.5 : i;
                double y_coord = 0.0;
 
                Node<2>* p_node = new Node<2>(node_index, true, x_coord, y_coord);
                nodes.push_back(p_node);
                node_index++;
            }
        }
        else
        {
            for (unsigned i = 0; i <= numElementsAcross; i++)
            {
                double x_coord = ((j%4 == 0)||(j%4 == 3)) ? i + 0.5 : i;
                double y_coord = (1.5*j - 0.5*(j%2))*0.5/sqrt(3.0);
                bool is_boundary_node = (j==1 || j==2*numElementsUp || i==0 || i==numElementsAcross) ? true : false;
 
                Node<2>* p_node = new Node<2>(node_index, is_boundary_node, x_coord, y_coord);
                nodes.push_back(p_node);
                node_index++;
            }
        }
    }
 
    /*
     * On the last row we have numElementsAcross nodes, all of which are boundary nodes.
     */
    double y_coord = (1.5*(2*numElementsUp+1) - 0.5*((2*numElementsUp+1)%2))*0.5/sqrt(3.0);
    if (((2*numElementsUp+1)%4 == 0)||((2*numElementsUp+1)%4 == 3))
    {
        Node<2>* p_node = new Node<2>(node_index, true, 0.5, y_coord);
        nodes.push_back(p_node);
        node_index++;
    }
    for (unsigned i=1; i<numElementsAcross; i++)
    {
        double x_coord = (((2*numElementsUp+1)%4 == 0)||((2*numElementsUp+1)%4 == 3)) ? i+0.5 : i;
 
        Node<2>* p_node = new Node<2>(node_index, true, x_coord, y_coord);
        nodes.push_back(p_node);
        node_index++;
    }
    if (((2*numElementsUp+1)%4 == 1)||((2*numElementsUp+1)%4 == 2))
    {
        Node<2>* p_node = new Node<2>(node_index, true, numElementsAcross, y_coord);
        nodes.push_back(p_node);
        node_index++;
    }
 
    /*
     * Create the elements. The array node_indices contains the
     * global node indices from bottom, going anticlockwise.
     */
    for (unsigned j = 0; j < numElementsUp; j++)
    {
        if (j == 0 && isFlatBottom)
        {
            unsigned short_node_indices[5];
            for (unsigned i = 0; i < numElementsAcross; i++)
            {
                short_node_indices[0] = i;
                short_node_indices[1] = i + 1;
                short_node_indices[2] = short_node_indices[1] + numElementsAcross + 1;
                short_node_indices[3] = short_node_indices[2] + numElementsAcross;
                short_node_indices[4] = short_node_indices[2] - 1;
 
                std::vector<Node<2>*> element_nodes;
                for (unsigned k = 0; k < 5; k++)
                {
                    element_nodes.push_back(nodes[short_node_indices[k]]);
                }
 
                element_index = j*numElementsAcross + i;
                VertexElement<2,2>* p_element = new VertexElement<2,2>(element_index, element_nodes);
                elements.push_back(p_element);
            }
        }
        else
        {
            for (unsigned i = 0; i < numElementsAcross; i++)
            {
                if (j == 0)
                {
                    node_indices[0] = i;
                }
                else
                {
                    unsigned first_index;
                    if (isFlatBottom)
                    {
                        first_index = 2*j*(numElementsAcross+1) - 1*(j%2==0) + i - numElementsAcross;
                    }
                    else
                    {
                        first_index = 2*j*(numElementsAcross+1) - 1*(j%2==0) + i;
                    }
                    node_indices[0] = first_index; // different for even/odd rows
                }
                node_indices[1] = node_indices[0] + numElementsAcross + 1 + 1*(j%2==0 && j>0);
                node_indices[2] = node_indices[1] + numElementsAcross + 1;
                node_indices[3] = node_indices[2] + numElementsAcross + 1*(j%2==1 && j<numElementsUp-1);
                node_indices[4] = node_indices[2] - 1;
                node_indices[5] = node_indices[1] - 1;
 
                std::vector<Node<2>*> element_nodes;
                for (unsigned k = 0; k < 6; k++)
                {
                    element_nodes.push_back(nodes[node_indices[k]]);
                }
 
                element_index = j*numElementsAcross + i;
                VertexElement<2,2>* p_element = new VertexElement<2,2>(element_index, element_nodes);
                elements.push_back(p_element);
            }
        }
    }
 
    mpMesh = boost::make_shared<MutableVertexMesh<2,2> >(nodes, elements, cellRearrangementThreshold, t2Threshold);
 
 
    // Scale the mesh so that each element's area takes the value elementArea
    mpMesh->Scale(sqrt(elementArea*2.0/sqrt(3.0)), sqrt(elementArea*2.0/sqrt(3.0)));
}
 
boost::shared_ptr<MutableVertexMesh<2,2> > HoneycombVertexMeshGenerator::GetMesh()
{
    return mpMesh;
}