Tag Archives: 3d

Like a Cat Scan of a Building

View of “internal organs”

Using a medical analogy to understand new ways of accessing point cloud data… The slide above shows the point cloud in RECAP software with the exterior envelope layer turned off, revealing the cluster of internal spaces.

The slides below show a series of “slices” taken vertically through the buildings at 1 meter intervals, from north towards the south and then from east proceeding towards the west.

a series of “slices” ex. 1

a series of “slices” ex. 2

Aerial Photography > Dense Point Clouds

Since 2009 I’ve done a fair amount of work with aerial photography, all the while continuing to explore architectural photography and photogrammetry while on the ground. I’ve tried in the past with some success to merge the two things but have found the results to be lacking something. That something, I think, is the hyper dense point cloud – and now I have it pretty much figured out.

Below are tow animated GIF images showing first the point cloud describing our local hospital (which I was contracted to cover with aerial photographs a few years back) and the second is a textured 3-D model of the scan.

Its so amazing to think that the flight over this structure can be reconstructed virtually a few years later with even more options to “fly around”…

Dense Point Cloud

Dense Point Cloud

Textured 3-D model

Textured 3-D model

The Clocktower Building in Staunton, VA

Three views of a model of this iconic corner building

Three views of a model of this iconic corner building

Just a quick share of the results of a test project to evaluate some new technology. Check out the video below to see all three views above in their 3D context.

A New way to use Photogrammetry (as a design tool)

Wireframe model projected accurately back into photograph

Typically I use photogrammetry to measure and draw existing structures.  Recently I’ve started using it also to visualize new structures. The photo above shows an image that was used originally to create a set of measured drawings of an existing house.  Once I had those drawings completed I designed a new structure to be built above the foundation of an existing garage.  I made a simple 3-D model of the new design and then accurately projected the model back into the photograph. This has been an invaluable tool in getting my client to understand the new design.

Alternate View

More on this new way of working to come…

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

Understanding Photogrammetry thanks to Albrecht Durer

Understanding photogrammetry thanks to Albrecht Durer

For me this drawing goes a long way towards explaining the geometry of capturing 3D points on a 2D plane. With this drawing we can better understand how a photograph is, in its essence, a relationship between a 2D plane and a single 3D point of view.  In photogrammetry, it is the precise understanding of the relationship between the focal point of a lens and the plane defined by the sensor (used to be the negative) that provides the basis for “back calculating” camera stations. When I read back what I’ve written it sopunds like gibberish. Its just not easy to explain. Probably an animation sould do the trick. in the mean time, looking at this picture above and the diagram below might help.

Stereo pair diagram