🧑‍💻 Structure From Motion

Here, we will talk about Structure from Motion, a technique that enables you to create 3D objects out of 2D photos. The information is divided into different chapters, as we sequentially progress within our course. The purpose of this resource is to prepare you for each course as part of your time for self-study (Selbststudium) as well as to operate as a general reference for the remainder of the term. It will not replace the content of the course, rather then be an additional resource. The content of this wiki is not equal to the content of the course!

Everything here is written in English and as always work in progress. As this is no traditional wiki, where you are able to participate, I still would enjoy your comments on this online resource. Thanks!

📸 Taking the photos

Chapter 1: Taking the photos

Here, you will learn how to take photos for SfM. It is a simple-enough process, but there are some points to consider. The equipment can be very basic (a simple camera or smartphone) to pretty elaborate (DSLR, Colour Chart, Coded Measures). However, the process of taking the photos is basically the same.
📖 Estimated reading time: 5 minutes -> Go to lesson!

Post-processing the photos

The post-processing of images taken with a DLSR is common to many methods, may it be just for.. well taking photos. RTI images have to undergo the same procedure however and this general tutorial will help us to proceed.
📖 Estimated reading time: 5 minutes

🛠️ Creating the 3D object

Chapter 2: Installing the software

There is various software available for doing Structure from Motion. The most famous one is Agisoft's Metashape. Other possibilities exist as well and depending on your choice, you need to install all necessary software.
📖 Estimated reading time: 1 minute

Chapter 3: Feature Detection

The first step towards a 3D object is to figure out where the features are and in what relation they are standing together. In this step, the software figures out where the cameras are and builds a sparse point cloud.
📖 Estimated reading time: 5 minutes

Chapter 4: Bundle Adjustment

A low-density point cloud looks nice, but you what looks even better? A high-density point cloud! Here we multiply the points and fill the gaps in between.
📖 Estimated reading time: 3 minutes

Chapter 5: Meshing the points

We still can see though our model, so we have to change that. Meshing connects points to polygons and polygons are solid. We therefore create a real 3D object out of our dense point cloud.
📖 Estimated reading time: 4,5 minutes

Chapter 6: Texturing the 3D model

Having the mesh ready, we still need some paint. With texturing, we will project the photos onto the mesh, so we have a fully textured 3D model as a result. After this step, you are basically done.
📖 Estimated reading time: 2,5 minutes

➕ Additional Content

Chapter 7: Exporting the model for archiving

Lastly, we want to save our model in a way, that we can open it later. Tomorrow, next year and next century. We therefore will choose a format that is open and free.
📖 Estimated reading time: 1,5 minutes

Chapter 8: Scaling the model

All is relative, so is your model. We have to scale it to the correct dimensions in order to really have it ready. We can do that within Metashape Professional as well, but in case you use the Standard version, here is a work-around.
📖 Estimated reading time: 3,5 minutes

Chapter 9: Combining two point clouds into one

If you want to create a real watertight 3D model, you need to combine at least two different point clouds. Here, I explain how to do that by the example of a stone-age bi-face.
📖 Estimated reading time: 5 minutes

Sitemap

• Chapter 1: Taking the photos
• Chapter 2: Installing Metashape
• Chapter 3: Feature Detection
• Chapter 4: Bundle Adjustment
• Chapter 5: Meshing the points
• Chapter 6: Texturing the 3D model
• Chapter 7: Exporting the model for archiving
• Chapter 8: Scaling the model
• Chapter 9: Combining two clouds into one