Point Clouds

Section View of Pointcloud – interior and exterior

from wikipedia: A point cloud is a set of data points in some coordinate system. In a three-dimensional coordinate system, these points are usually defined by X, Y, and Z coordinates, and often are intended to represent the external surface of an object. Point clouds may be created by 3D scanners.

>> And they can be created from photographs… (c’mon wikipedia – get up to date!) 😉

vaults over the nave at The Alamo

The Alamo: orthogonal view

The Alamo: orthogonal view of point cloud

 

Bethlehem Steel Blast Furnace Point Cloud

Bethlehem Steel Blast Furnace Point Cloud

k7You can tweak the sensitivity for portions of the scan in “post production”

k6medium

k5high

k4ultra

 

1

Luzerne County Courthouse – Wilkes-Barre, PA

A point cloud created by photogrammetry is a group of 3-D vertices associated with additional information such as color. In aggregate, millions of these points grouped together to form a sort of three dimensional model of the an object – a building, a sculpture, a landform, a face.

Preliminary point cloud depicting the Old Stone House in Newtown (Stephen's City, VA)

Preliminary point cloud depicting the Old Stone House in Newtown (Stephen’s City, VA)

Three views of a model of this iconic corner building

Three views of a model of this iconic corner building in Staunton, VA


 

 

 

 

 

previous:

Point cloud of an architectural urn at Kykuit generated through photogrammetry

point cloud is a set of vertices defined by XY, and Z coordinates which collectively represent the external surface of an object. With laser scanners, a point cloud is the sum of the measurements made from the device. With photogrammetry, the point cloud is the sum of measurements made from a series of overlapping photographs taken from a variety of vantage points. (In the image above, the green points are measurements while the red rectangles represent camera positions.)

For some time, point clouds have been more closely associated with laser scanners just as rectified imagery has been associated with photogrammetry. The two technologies are converging now. The quality of rectified images created from laser scans are getting closer to photography while the density of point clouds created by photogrammetry has become comparable to those made from lasers.

As usual with new technologies, point clouds are anything but static. The most provocative development in the world of point clouds has to do with their utility in and of themselves.  Until now the point cloud has served as a means to create either line drawings or some kind of 3D model (polygonal or triangle mesh models, NURBS surface models etc.)

In other words, point clouds have required a second step of surface reconstruction to become useful products.  I think that this will not be the case in a relatively short time.  In development now are technologies that will allow point clouds themselves to become enriched (or “hyper dense”) in such a way that they can be used as models themselves, available for extracting a new sort of ortho-photography.

selected photos of Goethean Hall – Franklin & Marshall

Point clouds created from photogrammetry can actually be considered four dimensional since each vertices corresponds to not only a 3D point in space but also a color associated with the material at the point of measurement. Below are some screen captures of the pint cloud generated from the images above.

Orthographic plan view of point cloud from above

Perspective view of point cloud (2)

See also this project page.

Advertisements