Shared intrinsics for all cameras

[colmap]

Shared intrinsics for all cameras

[sarlinpe]

Indeed, CameraMode defines how the cameras are shared across images and camera_model defines the type of camera (pinhole, radial, etc.) but the focal length is always inferred from the EXIF (image size + sensor specs) while the distortion parameters are initialized to zero.

To actually force a known camera, for now it is best to directly modify the database:

from hlco.utils.database import COLMAPDatabase
db = COLMAPDatabase.connect(database_path)
cam_id = 0
cam_tuple = (cam.model_id, cam.width, cam.height, tuple(cam.params))
db.add_camera(*cam_tuple, camera_id=cam_id)
for i, name in enumerate(sorted(image_list)):
    db.add_image(name, cam_id, image_id=i+1)
db.commit()
db.close()

We should instead bind ImageReaderOptions to have access to ImageReaderOptions.camera_params - you're welcome to submit a PR :)

[Phil26AT]

Yes, you can set shared intrinsics with camera_mode=pycolmap.CameraMode.SINGLE in hloc reconstruction or in pycolmap.import_images.

With shared intrinsics, COLMAP uses one camera for all images, and the intrinsics will be adjusted jointly during bundle adjustment.

[Zhu-Liyuan]

Thanks!

[aunagar]

Regarding shared / per image intrinsic. I see that we can set CameraMode SINGLE or PER_IMAGE. But where do we pass the known intrinsics? I see the option of adding camera_model, but not the actual intrinsic parameters in insert_images function.

Is it possible to pass the intrinsic parameters? If yes, how? Or is there any other way to assign cameras to the added images?

Thanks!

[zr19980402]

As the known camera intrinsic, some details to consult.
Firstly, "cam_tuple = (cam.model_id....) " If we should define a camera structure before the code
Secondly, shoud the image_list be put into the hloc function (import_images)

below are the codes.

details!
import_images is the hloc function.

[zr19980402]

if you want to use fixed camera paremeters, you can download the pycolmap source codes.

1. to change the images.cc you will find it use the colmap as the base. so you can change the ImageOption (class).
2. rebuild pycolmap & holc.