| Photography |

Photogrammetry

Photogrammetry, according to Wikipedia is the science of making measurements from photographs, especially for recovering the exact positions of surface points.

The input to photogrammetry are photographs, and the output is typically a map, a drawing, a measurement, or a 3D model of some real-world object or scene. Many of the maps we use today are created with photogrammetry and photographs taken from aircraft.

Photogrammetry can be classified several ways, but one standard method is to split the field based on camera location during photography. On this basis, we have Aerial Photogrammetry, and Terrestrial (or Close-Range) Photogrammetry and for our project, we used the second one: Terrestrial Photogrammetry.

Computational photogrammetry has been around since the early days of computers. The increasing power of computers, the introduction of the modern graphical user interface, and the introduction of the mouse in the 1980's and 1990's allowed computational photogrammetry to be run on everyday desktop computers. It was now a tool accessible to a wide audience.

Some of the existing software out there are General Applications (terrestrial & drone/UAV), Context Capture & Acute 3D, PhotoModeler, PhotoScan, Pix4dMapper, Reality Capture, Recap, just to mention a few.

For our project, Denton Florian, the Community Relations Manager in the Spirit of Texas Bank asked Epic Software Group to apply the concept of photogrammetry to represent the statues inside the bank as 3D models. The bank has an extensive collection of Texas art and historical memorabilia which they wish to share with the community. This artwork includes several sculptures in and around their headquarters and branch banks.

We choose RealityCapture which is a fully-featured application with a rich easy-to-use UI, extremely fast state-of-the-art core and with a set of unique features which pushes the envelope of what can be done with the photogrammetric methods

It’s an expensive software for 3D artist and professionals, but they offer a three months license to small businesses.

Steps:
 
-Requirements:
 
1. Camera (preferably with a high megapixel count) we used PANASONIC LUMIX FZ1000 4K Point and Shoot Camera with intervals every 4 seconds and 32 pictures in each row.
2. Photogrammetry software, in our case Reality Capture.
3. Turntable, for this one we ordered an intelligent electric turntable model: MT200RUL20.
4. Lights and flash diffusers for avoiding reflections in the object.
5. Patience (a lot of patience).


We choose exterior captures, more specifically singular objects.

Capture Process:

Position the object over the turntable and be sure you have the proper configuration in the camera, the timer, turntable and the lights. Then rotate the turntable between the intervals of the camera, set the camera to make sure you’ll take the right number of pictures needed. Repeat this process from different angles and take some close-up photos. The more the pictures the better.

Important things to remember in the capture process:  


Keep the lighting consistent

Capturing for alignment: To make sure that all your photos align as one 3D mode; your pictures need to overlap at least 30%.


Capturing for texture: The other important side of the capture method is to ensure you have close-up photos of the subject, to get those fine textures and geometry integrated into your scan.

Post Processing
 
This step is surprisingly simple, you don’t need a big knowledge of 3D modeling for this.
1. First, in the WORKFLOW tab in the Reality Capture software you will see a folder button, then just select the folder where you have all of your pictures.


2. For the second step, in the ALIGNMENT tab select “Align Images” and wait for a while.


3. After that in the RECONSTRUCTION tab select “Set Reconstruction Region->Set Region Automatically” to crop the “box” and select which points you wish to concentrate on.


4. For the fourth step in the same tab click on the “Normal Detail” or "High Detail" button, this will take more time, so you need to be patient, next click on “Texture”.


 
If you followed the steps correctly you will have a result like this
 

 

More Information

http://www.photogrammetry.com/

http://www.photogrammetry.com/photogrammetry-software.htm

https://medium.com/realities-io/getting-started-with-photogrammetry-d0a6ee40cb72