Unable to get sparse point cloud with colmap with 2 images with known pose

[NagabhushanSN95]

Hi,

I'm trying to train DS-NeRF on two images whose intrinsics and extrinsics are known. I followed this link you suggested in Issue-20, but colmap point_triangulator is failing because it triangulated 0 points.

To debug, I used the fern_2view data and ran imgs2poses.py to obtain camera params and point cloud. Then I followed the known-camera-poses procedure (I removed every second line in images.txt), but it fails even for that. In other words, for the exact same camera params for which first approach worked, the second approach didn't work. So, it can't be a problem with the data, but instead it should be something that I'm doing incorrectly.

I'm new to NeRF and Colmap. Can you please help me out.

More details:
I created a new folder fern_trial and in images folder, added the two images and renamed them as image001.png and image002.png. Also created an empty sparse folder.

This works:

fern_trial$ colmap feature_extractor --database_path database.db --image_path images --ImageReader.single_camera 1
fern_trial$ colmap exhaustive_matcher --database_path database.db
fern_trial$ colmap mapper --database_path database.db --image_path images --output_path sparse --Mapper.num_threads 16 --Mapper.init_min_tri_angle 4 --Mapper.multiple_models 0 --Mapper.extract_colors 0

This does not work:

fern_trial2$ colmap feature_extractor --database_path database.db --image_path images --ImageReader.single_camera 1

I copied camera.txt and images.txt (deleted every second line) from fern_trial to this folder.

fern_trial2$ colmap exhaustive_matcher --database_path database.db
fern_trial2$ colmap point_triangulator --database_path database.db --image_path images --input_path sparse/0 --output_path sparse2 --Mapper.num_threads 16 --Mapper.init_min_tri_angle 4 --Mapper.multiple_models 0 --Mapper.extract_colors 0

[NagabhushanSN95]

I was able to get this with an additional setting --Mapper.tri_ignore_two_view_tracks 0 for the point_triangulator