2RO045 - Volumetric Scanning

by Kristin Lucas

Introduction

Volumetric scanning is the process of digitally mapping physical objects and areas into x, y, z coordinates, forming a virtual point cloud geometry and a texture map that can be used for the purposes of digital archiving, analysis, asset creation for 3d software environments, and object reproduction through digital fabrication. The scanning process requires wired or wireless communication between scanning hardware and software.

Volumetric scanning technologies and methods have been developed for a variety of applications and use case priorities. Criteria are target type (object vs area), target size, geometry and texture resolution quality, portability of scanning technology, speed of capture, ease of use, and amount of post-capture artefact cleanup. Scanning technologies that produce both cloud point geometry and texture maps, include: infrared depth sensor scanning, photogrammetry, and laser scanning. They are available on the marketplace at wide-ranging price points, based on applications and use case priorities. A volumetric scanning report has been generated to outline the pros and cons of each approach and its investment costs.

Below is a breakdown of current volumetric scanning technology in three categories: Depth Sensor, Photogrammetry, and Laser.

Inexpensive: Depth Sensor scanning

  • Wireless Sensor

  • Wired Sensors

    • Advantage

      • Doesn’t require WiFi connection

    • Disadvantage

      • Requires a laptop and two people: one to hold laptop, one to hold sensor

      • It can get crowded with two people moving around an object so you need enough space

      • Depth scanners have short USB cables and do not function with standard USB extension cables. They require a specialized and expensive USB extension that can be ordered, but is not distributed in stores

    • Hardware

    • Software

      • Skanect Pro lets you export with or w/o color. 

      • Notice half of the body is in shadow. Subject was not evenly lit. Color in scan became muted/muddy on poorly lit side of body.

  • Overall Lighting Conditions

    • Requires a good amount of even lighting or the color of your model will translate poorly

    • Avoid harsh shadow, reflection and movement

    • Harsh light confuses the infrared reading of depth sensors

  • Space Requirements

    • Scanning requires at least 4 ft of space all the way around an object so that you can move all the way around the object at the same distance

    • Good to have object separated out from clutter in background. If this is unavoidable, it is recommended to set up a scrim to separate the model from the background

  • Overall Advantage of 3d scanning with depth sensors

    • Speed of capture

    • Small to human-scale object range (larger scale is untested)

    • Some available apps can scan rooms (crude look)

  • Overall Disadvantage of 3d scanning with depth sensors

    • Low resolution

    • Must move slowly or the scanner loses track of the model and you need to start over

    • Can leave holes in model in difficult places to scan. There is an autofill feature in the software but it doesn’t always yield the results you are looking for.

    • Clean up work to remove unwanted artefacts especially if lighting conditions are not ideal

    • Tall objects may require a ladder


Moderate: Photogrammetry

  • Setup

    • Hardware: DSLR camera

      • 24-50mm lens

      • Fixed focal length, do not change during shoot

      • Fixed aperture, do not change during shoot

      • Everything must be in focus

    • Software

    • Other

      • Ladder depending on size of object

  • Background

    • Setup black and white patterned markers in the background

      • Markers can be printed and placed at different heights around room such as on shelfs, sofa, tables, floor, etc

      • Alternately markers can be placed on stands or printed on scrims

      • Do not move the markers during the shoot, they are used for registration in post-processing

    • If background is too cluttered, set up scrims to reduce the visual noise, otherwise there may be a lot of post-processing cleanup work

      • Set scrims up far enough away from object that they do not interfere with photographing the object

  • Lighting Conditions

    • Good lighting or use tripod

    • Well-lit, even lighting

    • Avoid harsh shadows, reflection and movement

  • Photographic Tips

    • Generally 48+ photos are required depending on scale

    • 40% overlap of photos as you move around

      • First round of images

        • Fill 70% of frame with the object in the first round of image

      • Second round of images 

        • Ensures full coverage

        • Be sure sure to photograph undercuts and overhead angles or your model will process with holes in it

      • Third round (optional)

        • Record close up images in areas where you’d like to see more detail in your model

  • Overall Advantage

    • Texture recording is much better than with Depth Sensor scanning

    • small, medium and large scale scanning

  • Overall Disadvantage

    • Time-consuming

    • Clean up work

Expensive: Handheld Portable Scanners

    • Creaform Portable Scanners (contact company for price)

      • Creaform Scanners are designed to work with specific size objects

      • They used to have a package of two scanner models for different size objects

    • Artec Eva ($19,800, PC)

      • Artec Scanners are designed to work with specific size objects

  • Advantages

    • Speed

    • Mesh Accuracy

    • Color accuracy

    • Less clean up work

    • Freedom of movement while scanning

    • Communicates wirelessly to software

Expensive: Laser scanning


Conclusion

Our collective experience with volumetric scanning gives us a competitive edge in the art archiving marketplace. Our first step will be learning to 3D model rooms and buildings efficiently, ideally with software assistance. We hope to see some drone-based room scanning options on the market soon. 

The technology is still very new and experimental, but many companies are working on it. We don’t want to adapt a clumsy solution that will take lots of time and energy for a mediocre outcome. We also don’t want to spend $20,000 on an unfamiliar piece of equipment before we have steady income. We will keep a eye on the market, and stay ready to incorporate the right invention.

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