Thinking man

The Forgers

CS-6998 - 3D Photography - Fall 02

Team members: Alexei Masterov - David Smilowitz - Alejandro Troccoli - Sam Neymotin

Range Data Acquisiton

Le Penseur is located on Columbia's main campus, to the west of Philosophy hall and North of Kent Hall, as marked in yellow below.


Location of Le Penseur.

The scanning of Le Penseur took place on October 18th over the course of 3 hours. For registration purposes, we used a total of 16 targets. Three targets were attached to each side of the base and 1 target was mounted to each tower. There were 4 towers positioned around the base of the sculpture. This gave us a total of 16 targets to use for registration. Our first 4 scans were planned in such a way that we could capture 8 targets on each. This was done so that any additional scans only had to contain 3 targets. After taking the first 4 scans we registered them in Cyclone and planed the additional scans. Based on our observations we decided that 5 additional scans were needed to fill in the holes. Three of these scans were taken from the ground level and 2 of them from two windows on the 5 floor of Philosophy Hall. The French Department was extremely helpful since they allowed us to use their offices to scan the top of the sculpture.

 Registration of the scans was done using the Cyclone software and the targets. As mentioned above the first 4 scans were registered first. Then we added the 2 scans from the windows and finally the 3 remaining ground scans. This allowed us to detect errors in the target acquisition. We had problems with two targets because in both cases a tower partly occluded a target on the base. This partial occlusion caused the scanner to think the target was located on the tower when in reality it was on the base of the sculpture. We were able to identify this problem and removed the occluded targets from the registration process. Once we removed the misplaced targets the resulting registration was accurate.

The nine scans

Scan 1
Scan 2
Scan 3
Scan 4
Scan 5
Scan 6
Scan 7

Scan 8
Scan 9

Analysis of Scanning and Registration

Overall the scanning and registration process was a success. However there are some improvements that could be made. The main problem turned out to be the fact that the number of high scanning locations was limited. This was due to the positioning of nearby buildings and the presence of trees. The result was that only a minimal amount of data about some areas, such as the right hand, was captured. This lack of data made the meshing process much more difficult. The quality of the final point cloud would be increased if additional scans were taken from a tall moveable platform. Of course a more advanced scanner would also improve the detail contained in the model.

Highlights - Registered model movie

    Movie available (download 25Mb)

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