Photogrammetry is a technique that uses multiple photos to create 3D models. This article will show you how to plan a photogrammetry shoot, including what equipment you need and the software you’ll use for post-processing. We also have tips on how to take photos that are useful in the project post-processing phase (elevation, overlap).
What is photogrammetry and how does it work.
Photogrammetry is a process that goes beyond typical photography. It’s the process of using software to extrapolate 3D models from 2D photographs. This technology has been around for decades but in recent years it’s become popular with help from computer graphics and video game development. Photogrammetry can be used for all sorts of things like creating high-resolution terrain maps, accurate satellite images, or even generating realistic 3d recreations of archaeological sites.
Photogrammetric shoots are usually done by professional photographers who have experience in this area and they use specialized equipment to take photos at specific angles so that they will be useful during the post-processing phases such as elevation and overlap shots. Only professionals, until now.
Photogrammetry has become more and more accessible to everyone. Do you need some object or space for a rendering? Think about photo-scanning it. You no longer need to model and texture complex models from scratch. You can take a set of photos and turn them into an amazing photorealistic object.
Planning a photogrammetry shoot.
Planning a photogrammetry shoot may seem like a daunting task if you’re not familiar with the process. But, it’s really just about pre-planning and being prepared with the right equipment at the right time.
In order to create the best results from your shoot, you’ll need to plan carefully around five main considerations: Subject, Camera, Lighting, Setting, Software.
What is it you want to capture? It really can be anything. Something you see spur of the moment to something you have been planning to capture for months. Small to large.
What equipment is needed? There are two sets of equipment you’ll need — one while shooting and another once all of your images have been captured. Several years ago, most would say you need to have a DSLR in order to properly capture an object. I believe that is shifting to more working with the camera you have with you when you need to shoot that object. Most likely it’s your phone.
The first thing you’ll need to do is decide on what exactly you want your model for, as it will determine how you shoot and the process of post-processing.
Once you’ve decided on your project, figure out what angles and elevations you’ll need to get enough of a view of every part of the model that you want to be included in it. Be sure to leave enough overlap on multiple shots so that the program can properly line them up.
The last important step is to get as much detail in each shot as possible, and this usually means having an extremely high-resolution camera (50 megapixels or higher), but it’s not required. I use my iPhone 12 most often. It all depends on your needs and your level of detail needed. You can shoot with such a high resolution but it’s often not necessary.
While not crucial, a tripod is quite useful if you want your angles exactly the same on all of your shots. It’s also important that everything stays still while taking each shot (including yourself) so any movement will be visible and could damage your software’s potential of properly aligning the photographs.
Equipment needed for photogrammetry
The equipment needed for photogrammetry shoots includes:
- DSLR Camera or camera phone
- Cable release cord, maybe
- Light, maybe
Lighting is a key component in photogrammetry because the textures and shadows on an object are baked into the material of that object. Therefore harsh shadows or highlights will limit your ability to realistically light the object in your scene later.
A lighting setup that produces good even lighting results can often help when scanning indoors. When outside opt for a more overcast day.
Camera types for photogrammetry shoots
The image you are capturing is important in order to get the best model calculation but also the best textures from that image. It’s more important to have good lighting, sharp focus, and a steady hand than the highest resolution camera in the world.
Camera phones are now more powerful than ever, so if you already have one it’s highly likely that it will be able to do most of what an entry-level DSLR can. If the lighting isn’t too harsh and your photo is sharp enough then a phone would work.
Entry-level or higher-end DSLRs produce nice detailed images with good noise control at high ISOs which comes in very handy when shooting in less than ideal lighting conditions.
Software to use to plan a photo-shoot
Choosing the perfect software to plan a photogrammetry shoot is difficult because there are so many options.
Most people use one of these programs: Reality Capture, Metashape, or some of the newer iPhone apps like Trnio, Polycam, and more.
The desktop-based apps take more personal processing power than the iPhone apps that are using cloud computing. But oftentimes, if done correctly you can get higher-end results from something like Metashape.
The key thing when choosing a software package for photogrammetry optimization is the simplification of the workflow. Not every software has an easy-to-use interface so make sure that any pre-processing and post-processing steps are clear enough before purchasing.
Tips on how to take photos that will be useful in the project post-processing phase (elevation, overlap)
When trying to reconstruct an object with a 2D image you have to think about how the computer will piece all the elements together. It will try to track various parts of your image from one shot to the next. By determining how far each object moves in relation to the next will determine its place on the mesh. You need to take photographs that allow for the software to track the elements. Because of this highly reflective objects that are constantly changing the image they reflect confuses the software and its pixel tracking. You might want to dust heavily reflective objects with chalk spray.
When you start the photographing process, you must be methodical with your approach. I typically create three rings around my object. One low, one in the middle, and one high. Step around the model taking as many photos as you have time. Generally, one side step for each photo works well for me. Ensure each is in focus and capturing as much of the model as possible.
It’s best to try and keep one focal distance. Don’t zoom in and out of an object. This change in focal length can confuse the software and make the reconstruction overly difficult.
Have fun with it. Don’t rush the process if you want good results.