Update to Colmap 3.9.1 and added Dockerfile.

[pablospe]

This PR updates the changes made to Colmap 3.9 and adds a Dockerfile. Usage:

export COLMAP_VERSION=3.9.1
export CUDA_ARCHITECTURES=70
docker build -t pyceres \
    --build-arg COLMAP_VERSION=${COLMAP_VERSION}  \
    --build-arg CUDA_ARCHITECTURES=${CUDA_ARCHITECTURES}  \
    -f Dockerfile .

A possible improvement for a future pull request is to create a runtime docker stage that only installs the essential dependencies and uses the compiled ceres-solver and colmap from the builder stage (this will reduce the docker image size considerably).

[pablospe]

@Phil26AT @sarlinpe I was wondering if you could take a look to this PR.

[sarlinpe]

LGTM. I don't use Docker so I don't really understand all these details.

[sarlinpe]

@pablospe Since COLMAP 3.9.1 the quaternions follow the Eigen format (xyzw instead of wxyz) but this wasn't updated here - so the user need to manually handle any conversion.

[pablospe]

Yes, you are right, this is not handle it here. Should we revert these changes?

[sarlinpe]

I'd rather revert for now and do a proper upgrade in #27 - can you submit one and keep the Docker stuff if you need it?

[pablospe]

Yes, it makes sense to revert. I'll create another PR with only the Dockerfile. You could also take the changes from this PR, like the rename of WorldToImage for ImgFromCam: see in bundle.cc.

[pablospe]

One question, it only uses only the camera models from Colmap, right? I was wondering if it would make sense to simply take a copy the models.h to avoid Colmap dependency in this repo? It is like a circular dependency, for compiling Colmap you need ceres, and for pyceres you need Colmap :)

[sarlinpe]

My plan is to move the bundle & PGO cost functions to pycolmap, such that pyceres handles only the core features without any dependency on COLMAP. But this requires some updates upstream to add covariances.

[pablospe]

Related PR (for the Dockerfile part): #31