Add EQUIRECTANGULAR camera model support for 360° images

[zalo]

Summary

Add support for equirectangular (360° panoramic) camera model to enable global SfM reconstruction with 360° cameras like Insta360, Ricoh Theta, etc.

Changes

1. Camera model support (glomap/scene/types_sfm.h)

   • Add EQUIRECTANGULAR to CameraModelId enum (ID 10, matching COLMAP)
   • Register in camera model switch macros

2. Intrinsic handling (glomap/scene/types_sfm.cc)

   • Add case for EQUIRECTANGULAR in Camera::GetK() (returns identity - no focal length)
   • Add case in InitializeCamera() for EQUIRECTANGULAR model

3. CMake configuration (cmake/FindDependencies.cmake)

   • Configure to use local COLMAP and PoseLib builds with equirectangular support
   • Uses FetchContent to pull from feature branches

Dependencies

This PR depends on equirectangular support being merged in:

• COLMAP: Add EQUIRECTANGULAR camera model for 360° panoramic images colmap#4014
• PoseLib: Add EQUIRECTANGULAR camera model support for 360° images PoseLib/PoseLib#178

Test plan

• Build passes with local COLMAP/PoseLib
• Successfully reconstructed 330-image 360° panoramic dataset
• Output: 26,384 3D points, 1.09px mean reprojection error

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds support for the EQUIRECTANGULAR camera model to enable global SfM reconstruction with 360° panoramic cameras. The implementation detects spherical camera models and provides compatibility shims for methods that assume perspective projection, while excluding them from focal length calibration.

Changes:

• Added IsSpherical() method to detect equirectangular/spherical camera models and adapted Focal(), PrincipalPoint(), and GetK() to return compatibility values for spherical cameras
• Modified view graph calibration to skip spherical cameras during focal length estimation
• Updated CMake configuration to use local COLMAP and PoseLib builds with equirectangular support

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
glomap/scene/camera.h	Adds spherical camera detection and compatibility methods for cameras without traditional intrinsics
glomap/estimators/view_graph_calibration.cc	Excludes spherical cameras from focal length calibration optimization
cmake/FindDependencies.cmake	Configures build to use local dependency versions with equirectangular support

Comments suppressed due to low confidence (1)

glomap/estimators/view_graph_calibration.cc:185

• Potential index mismatch bug. The FilterImagePairs method iterates through all valid image pairs and accesses residuals by counter, but AddImagePair skips spherical camera pairs without adding residuals to the problem. This means counter will advance for spherical pairs in FilterImagePairs, but no corresponding residuals exist, causing an out-of-bounds access or misaligned residual reading. Need to skip spherical camera pairs in FilterImagePairs similar to AddImagePair.

  for (auto& [image_pair_id, image_pair] : view_graph.image_pairs) {
    if (image_pair.config != colmap::TwoViewGeometry::CALIBRATED &&
        image_pair.config != colmap::TwoViewGeometry::UNCALIBRATED)
      continue;
    if (image_pair.is_valid == false) continue;

    const Eigen::Vector2d error(residuals[counter], residuals[counter + 1]);

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[ichsan2895]

This is a great feature.

Recently, 360 videos into 3DGS is more popular. Instead of creates cubemap/planar of equirectangular images, it can directly train the equirectangular images with Lichtfeld-Studio/others that has GUT feature.

Only agisoft metashape that can handle equirectangular poses. Hopefully glomap can handle it too.