#include "gridmesh.h"

GridMesh::GridMesh(int width, int height, bool alternate) : Mesh(), m_width(width), m_height(height)
{
    for(int i=0; i<=width; ++i)
    {
        for(int j=0; j<=height; ++j)
        {
            Vertex v;
            v.position = glm::vec3((float)i/(float)width, (float)j/(float)height, 0);
            v.normal = glm::vec3(0, 0, 1);
            v.texCoord = glm::vec2(v.position.x, v.position.y);
            addVertex(v);
            if(i > 0 && j > 0)
            {
                if(alternate && (i+j)%2)
                {
                    addFace(getVertexId(i, j),
                            getVertexId(i-1, j),
                            getVertexId(i, j-1));
                    addFace(getVertexId(i-1, j-1),
                            getVertexId(i, j-1),
                            getVertexId(i-1, j));
                }
                else
                {
                    addFace(getVertexId(i, j),
                            getVertexId(i-1, j),
                            getVertexId(i-1, j-1));
                    addFace(getVertexId(i, j),
                            getVertexId(i-1, j-1),
                            getVertexId(i, j-1));
                }
            }
        }
    }
}

int GridMesh::getVertexId(int i, int j)
{
    return i*(m_height+1) + j;
}