On the left is a photograph of Michelangelo's David. On the right is a computer rendering made from a geometric model. Constructed in December, 1999 at a resolution of 1.0 mm, the model is watertight and contains 4 million polygons. For a brief overview of the steps required to build this model, click here. The coloring in this model was computed from digitized color images using the procedure outlined here. For a more detailed description of these procedures, refer to our Siggraph 2000 paper.
Although this model looks fairly good, we are nowhere near our goal of building a full-resolution (0.29 mm) model. The full-resolution data for this part of the statue contains 480 million polygons and 2,000 color images. Here's a tiny sample of our full-resolution dataset. Frankly, we are finding it challenging to clean up, align, merge, and process this much geometric and color data. To see the most complex geometric model we've built to date, look at figure 4 on our page of renderings of St. Matthew.
By the way, the photograph (at left) was taken under uncalibrated conditions, so its viewpoint and illumination differ slightly from those in the rendering. Other differences between the photograph and the rendering are that the photograph has shadows while the rendering does not, and the photograph has a finite depth of field while the rendering is in perfect focus. We're working on fixing these differences.
(Warning - these images are large! The 3rd one is 2K x 2K pixels)
Computer renderings made in December, 1999 by Henrik Wann Jensen from a 2.0 mm, 8-million polygon model of the entire statue. The veining and reflectance are artificial. The renderings include physically correct subsurface scattering, but with arbitrary parameters.
Aside from the artificial coloring, this model, created in June of 1999, has many problems: noisy data, misaligned meshes, holes, etc. We think of this image as our "to-do list." Our ultimate goal, of course, is a flawless, watertight, full-resolution model of the entire statue, with color. The raw data for this task consists of 2 billion polygons and 7,000 color images, occupying 32 gigabytes.
If you want to fly around this model of the David (without color), but you don't qualify for a license to download the data, try ScanView: our secure client / server rendering system.
The image at left is an outtake - a mistake we made while tuning our rendering parameters for the December 1999 renderings shown in the previous section. Specifically, the depth of subsurface scattering was set too high. It's an intersting image, though, because it helps us explore our assumptions about surface appearance. Most observers say this looks like an onyx replica of David's head that measures about 6 inches across. Apparently, we have strong notions about the absolute scale of subsurface scattering in onyx. The perceptual effects of subsurface scattering are explored further in our Siggraph 2001 paper on subsurface light transport.
The David has been waxed several times during his history, and conservators would like to know which parts of the statue are still coated. Fortunately, wax fluoresces when illuminated with ultraviolet light. The image at right is an unretouched digital photograph of David's head taken under ultraviolet light. The light-colored patches on his left cheek and forehead are probably wax. This photograph is one image from a full-length ultraviolet "portrait" we made of the David during our year in Italy. We are currently mapping this data onto our polygon mesh model, thereby producing a per-vertex UV fluorescence map. This map will be used to help restorers plan a major cleaning of the statue that is scheduled to begin in Autumn of 2001.
Note that the absolute intensity of the fluorescence was low, forcing us to raise the gain on our camera; this accounts for the noisy appearance of this image under magnification. The blueness near silhouettes, for example on top of his head and shoulder, are a physical artifact, not a digital one, caused by fluorescent scattering from dusty surfaces viewed at a grazing angle. This problem is endemic in UV imaging, so conservators are trained to ignore it. However, since we have acquired UV images from multiple directions, and we have a 3D model of the statue, we can discard grazing-angle pixels when mapping the data onto our model. This will permit us to produce a UV map that is free of this particular artifact.
Notice: The images of Michelangelo's statues that appear on this web page are the property of the Digital Michelangelo Project and the Soprintendenza ai beni artistici e storici per le province di Firenze, Pistoia, e Prato. They may not be copied, downloaded and stored, forwarded, or reproduced in any form, including electronic forms such as email or the web, by any persons, regardless of purpose, without express written permission from the project director Marc Levoy. Any commerical use also requires written permission from the Soprintendenza.
Notizia: Questi modelli elaborati al computer, immagini computerizzate, e fotografiche sono propriet� del Progetto Digitale Michelangelo e la Soprintendenza Per I Beni Artistici e Storici per le Province di Firenze, Pistoia e Prato. Non possono essere copiati, scaricati da internet su un file, inviati, o riprodotti in nessuna forma, incluso la posta elettronica o il web, da nessuna persona per nessun motivo, senza un permesso scritto da Marc Levoy, il direttore del progetto. Eventuali usi commerciali esigono anche il permesso scritto dalla Soprintendenza.