Fig 1. 3D Phong rendering and colored light system.

Principle of the 3D Phong rendering illustrated with the URC of MLD11-30. Illumination of the 3D model simultaneously by two light sources (LS1 and LS2), each composed of three components (three first columns): ambient, diffuse and specular. Each of the three rows (left half of the picture) shows the individual effect of each component. The combination of all light components is presented in the fourth column. LS1 (middle row) employs a white hue and is oriented in a perpendicular direction to the computer screen (viewer’s perspective—labial side of the crown). Light source 2 has a low white ambient (5 in VGStudio MAX 2.2), an orange diffuse light of moderate intensity (35) and a pale blue specular component with a tenfold higher intensity than the orange light (about 200). Combined with LS1, LS2 is oriented from the top (for taking a first set of images during the rotation of the tooth when mounting a multiple view plate, see S1 Fig), and then from the bottom (second set of images, same conditions) to light the 3D model with a low angle incidence to make topographical and densitometric details more visible. Both sets of images were then combined in Adobe Photoshop to enhance and sharpen topographic details with a mask of high frequency reinforcement. This operation involved taking the top-light image and subtracting structures smaller than 20 pixels that were also present in the bottom-light image (low frequencies), resulting in the combination of unique details from each direction in the final 3D model (far right). File name: Figure_1.tif.