def _shadow_blob(x, y, z, cmap_indices, cmap, scale, mlab):
    """Shows blobs as shadows projected parallel to the 3D visualization.
    
    Parmas:
        x: Array of x-coordinates of blobs.
        y: Array of y-coordinates of blobs.
        z: Array of z-coordinates of blobs.
        cmap_indices: Indices of blobs for the colormap, usually given as a
            simple ascending sequence the same size as the number of blobs.
        cmap: The colormap, usually the same as for the segments.
        scale: Array of scaled size of each blob.
        mlab: Mayavi object.
    """
    pts_shadows = mlab.points3d(x, y, z, cmap_indices, 
                                          mode="2dcircle", scale_mode="none", 
                                          scale_factor=scale*0.8, resolution=20)
    pts_shadows.module_manager.scalar_lut_manager.lut.table = cmap
    return pts_shadows