Photogrammetry Explained

Photogrammetry Explained

Photogrammetry is the science of measuring objects from photographs. In VFX, it means taking a series of overlapping photos of a real object or location and using software to reconstruct it as a 3D model. The result is a highly detailed digital replica with photorealistic textures automatically generated from the photos. This is one of the most powerful techniques for creating realistic 3D assets quickly.

The capture process is straightforward but requires discipline. You photograph the subject from every angle, making sure each photo overlaps with the next by at least sixty percent. The software needs to see the same features from multiple viewpoints to calculate their 3D positions. Good lighting is important. Diffuse, even lighting without harsh shadows gives the best results. Specular highlights can confuse the software because they move as you change position.

The software works in stages. First, it detects distinctive features in each photo, like corners, edges, and textured spots. Then it matches these features across different photos. Using the matched features, it calculates the camera position for each photo and the 3D position of each feature point. This creates a sparse point cloud. Then comes the dense reconstruction, where the software guesses the 3D position of every pixel to create a dense point cloud or mesh.

Popular photogrammetry software includes RealityCapture, Agisoft Metashape, and Meshroom. RealityCapture is known for being extremely fast and producing high quality results. Metashape has a gentle learning curve and is widely used. Meshroom is free and open source but slower. All of them can export textured meshes in standard formats like OBJ, FBX, and Alembic that you can import into any 3D package.

Photogrammetry has limitations. Transparent and reflective objects are very difficult because the software cannot consistently track features through them. Moving objects like trees in the wind need to be frozen. Very large environments require hundreds or thousands of photos. But for capturing real world props, sets, and locations, it is unmatched in speed and realism. Many blockbuster movies use photogrammetry to digitize actors, vehicles, and entire cities.