#include "gridmesh.h"

GridMesh::GridMesh(int width, int height, bool alternate)
{
    for(int i=0; i<=width; ++i)
    {
        for(int j=0; j<=height; ++j)
        {
            float x = (float)i/(float)width;
            float y = (float)j/(float)height;
            addPosition(x, y, 0);
            addNormal(0, 0, 1);
            addTexCoord(x, y);
            if(i > 0 && j > 0)
            {
                if(alternate && (i+j)%2)
                {
                    addTriangle(getVertexId(i, j, height),
                                getVertexId(i-1, j, height),
                                getVertexId(i, j-1, height));
                    addTriangle(getVertexId(i-1, j-1, height),
                                getVertexId(i, j-1, height),
                                getVertexId(i-1, j, height));
                }
                else
                {
                    addTriangle(getVertexId(i, j, height),
                                getVertexId(i-1, j, height),
                                getVertexId(i-1, j-1, height));
                    addTriangle(getVertexId(i, j, height),
                                getVertexId(i-1, j-1, height),
                                getVertexId(i, j-1, height));
                }
            }
        }
    }
}

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