from SimPEG import *

def run(plotIt=True):
    """
        Mesh: QuadTree: Hanging Nodes
        =============================

        You can give the refine method a function, which is evaluated on every cell
        of the TreeMesh.

        Occasionally it is useful to initially refine to a constant level
        (e.g. 3 in this 32x32 mesh). This means the function is first evaluated
        on an 8x8 mesh (2^3).

    """
    M = Mesh.TreeMesh([8,8])
    def function(cell):
        xyz = cell.center
        dist = ((xyz - [0.25,0.25])**2).sum()**0.5
        if dist < 0.25:
            return 3
        return 2
    M.refine(function);
    M.number()
    if plotIt:
        import matplotlib.pyplot as plt
        M.plotGrid(nodes=True, cells=True, facesX=True)
        plt.legend(('Grid', 'Cell Centers', 'Nodes', 'Hanging Nodes', 'X faces', 'Hanging X faces'))
        plt.show()

if __name__ == '__main__':
    run()