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12: Duveen Gallery Interior
In 1799, the British and the French were competing in their rush to acquire the treasured antiquities of the ancient world. The British had just captured the Rosette Stone from the French; which the French in turn had discovered in the western delta of the Nile. Meanwhile Lord Elgin originally undertook a project to copy the architecture and sculptures of the Parthenon for his personal estate. In early 1801, he was able to use his connections as British ambassador to Constantinople to get a broader mandate to remove 'some pieces of stone with inscriptions and figures' from the Parthenon. By 1803 several hundred pieces of sculptured marble, including a column from the Erechtheion, seventeen figures from the Parthenon pediments and fifteen metopes, were boxed in 200 chests waiting to be shipped back to Scotland.
While the majority of the cases containing the marbles had arrived in England by 1805, war had broken out between England and Turkey and the French had re-established themselves in Athens. It was not until 1812 that all the marbles arrived in England. Lord Elgin, sticken by debt, was forced to sell the sculptures to the British government in 1916, for £35,000. The sculptures were then placed on display in the British museum. Following a controversial cleaning of the sculptures in the 1930s, Lord Duveen funded a gallery dedicated to housing the Parthenon Sculptures. Building continued from 1936 to 1938, though due to damage sustained during World War II the gallery did not fully open till 1962.
This establishing shot shows the sculptures in their current position
in the gallery. The virtual Duveen gallery was constructed primarily
from Canon D30 images taken in July 2001 (just after that summer's
Eurographics Workshop on Rendering). Since it was undesirable to use
laser scanning in the heavily-trafficked gallery, we opted for a
photogrammetric approach to accurately model the dimensions of the
room. Additional architectural details, scene geometry, and textures
were modelled using Maya. In order to capture the illumination within
the gallery, we took high dynamic range images of the skylight.
Texture photographs were taken of the principal surfaces in the room,
each placed in a radiometrically calibrated space using a Macbeth
ColorChecker chart.
Once the room had been modelled it was possible to incorporate
the frieze, pediment, and metope sculptures from the Basel
Skulpturhalle scanning trip. More details of this process are
included in the explanation of the 4th Sequence.
Photometric modelling of the
gallery: To obtain accurate dimensions, a simplified model of the Duveen
gallery was modelled using the Facade photometric modelling
system. The Facade program uses line correspondences between
images and geometry primitives to solve for camera positions and
geometric dimensions. Facade was used to measure the size of the hall
walls, doors, pedestals, columns, skylights, and sculptures. The
images on the right show one source image with marked correspondences,
and the resulting model of the main gallery. |
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Baked-in lighting:
Contributing to the scene's realism is the soft specular reflection on the floor. As the only light source in the scene is a large area sky-light, this reflection would be costly to render using Monte-Carlo global illumination to reflect the image-based light source of the skylight. Our solution was to render a separate specular pass for the floor leveraging image-based rendering. The first stage was to render the sequence with diffuse floor with no specular reflection. Then we projected the rendered frames back onto the simplified version of the gallery geometry. Finally we rendered the scene with the specular floor, with the simplified geometry set as emissive. This second pass rendered very quickly as it requires no diffuse light bounces. The images on the right show the separate diffuse and specular renders.
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13: Museum Dedication
An inscription in the wall of gallery, commemorates the construction of the exhibit. We slightly repositioned the inscription of the wall to make it more legible, and included the glass display case and the frieze in the shot for visual interest and continuity.
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Shot
14: The Remains of Poseidon
One of the most dramatic sculptures in the gallery is the fragmented torso of Poseidon which originally was central to the Parthenon's West pediment. Though the Basel Skulpturhalle contained a cast of the Poseidon torso, the cast had been augmented with reconstructions of the head and limbs and joined with a cast of the front slab which is in Athens. Lacking accurate 3D geometry of this sculpture, we chose an image-based view-interpolation approach. During the July 2001 British Museum visit, a set of photographes were taken rotating around the Poseidon sculpture. For this shot we interpolate between four of these images with view-dependent texture mapping onto geometry derived from the photographs.
Storyboard: Artistic previsialization of the Poseidon torso by Marc Brownlow.
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Model of Poseidon: After a set of point correspondences were manually selected between the images, a course mesh was generated by triangulating these 3d points. To generate additional control points, the mesh was subdivided using a ---- algorithm. Using a weighted influence, points in each image were simultaneously aligned towards hand marked silhouettes. This was iterated across each image until a suitable mesh was generated. This technique is described in a SIGGRAPH 2005 poster.
Finally we rendered the model using a simple form of view-dependent texture mapping. As the vitual camera moved along a path which interpolates the original camera positions, we textured the model projectively by blending the photographs corresponding to the two closest cameras. We used a simple z-buffer technique to assure that surfaces which are hidden in one of the original camera views are not textured using that camera.
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