In religious art the halo can symbolise divine or sanctified status, or it can be used to distinguish a remarkable contemporary person. Saints are usually represented with a circular halo of heavenly light around their head, either in the form of a round disc or rays of gold lines. Sometimes the name of the saint is inscribed within the halo, and the Virgin Mary's halo can include the words 'Ave Maria Gratia Plena' (Hail Mary, full of grace) - the words of greeting said to her at the Annunciation by the Archangel Gabriel. Christ's halo often contains the shape of a cross within it.
However, not all haloes are circular: God the Father sometimes has a triangular shaped halo to symbolise the Trinity. Popes, emperors and donors may have square shaped halos, and allegorical figures such as the Virtues and Vices can have hexagonal ones.
The hexagonal halo of the pointing centurion in the Crucifixion scene is peculiar to Bernardo Daddi's workshop. It is also seen in his Crucifixion panel no.14 in the Staatliches Lindenau Kunst Museum, Altenburg. It was probably used to differentiate the centurion, not only from the saintly persons on the opposite side of the cross, but also from the other soldiers in the crowd since, unlike the centurion, they did not recognise Christ's divinity.
