three dimensional model can be constructed including faces and textures if desired fig6 a c 7 a c and 8 a c are examples of two dimensional spatial graphs processed as described above fig6 a 7 a and 8 a show the two dimensional spatial graphs fig6 b 7 b and 8 b show the edge types assigned and fig6 c 7 c and 8 c show the three dimensional models reconstructed from the edge types in fig6 b 7 b and 8 b e and r stand for eave and rake and r v and h stand for ridge valley and hip in fig8 a the middle square is identified on the spatial graph as not a roof face indicating a central courtyard if it were a roof face a different roof shape would have been constructed creating a three dimensional representation of the roof allows for the further calculation of the azimuth geographic orientation e g se 135 u00b0 of roof faces one way of doing this is taking the projection of the normal of the roof face onto the ground plane and calculating its angle relative to a vector pointing north if using satellite imagery to create the graph the absolute size of the three dimensional structure can be determined from the scale of the imagery used to construct the graph fig3 a c 4 5 6 a c 7 a c and 8 a c are a simplified.