Colmap no good initial image pair found

1. Does Colmap need GPU?
2. How does COLMAP work?
3. What is Colmap?

Does Colmap need GPU?

Available functionality without GPU/CUDA

If you do not have a CUDA-enabled GPU but some other GPU, you can use all COLMAP functionality except the dense reconstruction part. However, you can use external dense reconstruction software as an alternative, as described in the Tutorial.

How does COLMAP work?

COLMAP first loads all extracted data from the database into memory and seeds the reconstruction from an initial image pair. Then, the scene is incrementally extended by registering new images and triangulating new points. The results are visualized in “real-time” during this reconstruction process.

What is Colmap?

COLMAP is a general-purpose Structure-from-Motion (SfM) and Multi-View Stereo (MVS) pipeline with a graphical and command-line interface. It offers a wide range of features for reconstruction of ordered and unordered image collections. The software is licensed under the new BSD license.