Tag Archives: sculpture

Documentation of a sculptural element using Photogrammetry

Test subject

In August I shot a variety of sculptural objects with a mind towards testing the capabilities of photogrammetric software to create useful point cloud descriptions of objects that are difficult to assess conventionally. This urn represents a little of both – parts of its form is sculptural, organic, non repeating, while parts are more classical or architectural in  nature.

Photo with magnifying glass (or ‘loupe’) in Elcovision software

For this study I processed 72 photographs which consisted of three sets of images: two rings around the urn at 16mm and a half arc at 50mm (spatial constraints made it impossible to go all the way around at 50mm).

Point Cloud and photo stations (in red)

60,000 points were generated to describe the urn itself.  When viewed orthographically the point cloud behaves like a drawing – or can be the basis for a measured drawing.  The sculptural relief of the figures still escapes precise documentation in the point cloud, I think.  Laser scans still do this fine detail better, it seems.  But this point cloud – even as it is – in combination with  the photographs do so much more than what photogrammetry was able to do even a year or so ago. I think its catching up to laser sourced point clouds and doesn’t require the huge equipment investment.

Orthographic View of Point Cloud

Documentation of a sculptural element using Photogrammetry

Test subject

In August I shot a variety of sculptural objects with a mind towards testing the capabilities of photogrammetric software to create useful point cloud descriptions of objects that are difficult to assess conventionally. This urn represents a little of both – parts of its form is sculptural, organic, non repeating, while parts are more classical or architectural in  nature.

Photo with magnifying glass or loupe in Elcovision software

For this study I processed 72 photographs which consisted of three sets of images: two rings around the urn at 16mm and a half arc at 50mm (spatial constraints made it impossible to go all the way around at 50mm).

Point Cloud and photo stations (in red)

60,000 points were generated to describe the urn itself.  When viewed orthographically the point cloud behaves like a drawing – or can be the basis for a measured drawing.  The sculptural relief of the figures still escapes precise documentation in the point cloud, I think.  Laser scans still do this fine detail better, it seems.  But this point cloud – even as it is – in combination with  the photographs do so much more than what photogrammetry was able to do even a year or so ago. I think its catching up to laser sourced point clouds and doesn’t require the huge equipment investment.

Orthographic View of Point Cloud

Reclining Figure Arch Leg – Sculpture by Henry Moore 1973

Reclining Figure Arch Leg – by Henry Moore 1973

This summer (2010) marks the real debut of a reliable automatic generation of dense point clouds by using photogrammetry.  I travelled to Switzerland in July and gave this exciting new software module a try on something that would be a real challenge to document in anyway other way – a sculpture by Henry Moore.

The four panels below show different views of the point cloud generated from these photographs. For me the real lesson in this study is that objects to be documented in this way need to be photographed in conditions that produce as even lighting as possible. One can see that some of the reflectiveness from the metal (brass) surface of the sculpture resulted in less-dense-than-desired regions in the point cloud. Still, I was excited to see how well it performed under what I now understand to be relatively harsh conditions.

The density of these point clouds is considerably higher than what photogrammetry ordinarily would produce while not being the hard-to-manage overkill produced by laser scans. what’s more, these point clouds can be enriched with the same type of smart point clouds that provide a meaningful link to both rectified photography and architectural description.