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Store log_scale instead of scale in colmap::Sim3d #3494

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B1ueber2y wants to merge 6 commits into from
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Store log_scale instead of scale in colmap::Sim3d #3494

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@B1ueber2y B1ueber2y commented Jul 17, 2025 •
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log_scale spans the full space and has benefits in optimization. Storing log_scale instead of scale avoids invalid sim3d object with negative scale.

The python interfaces for sim3d.scale are kept unchanged, while the C++ interfaces change to SetScale(scale) and GetScale(). Update the cost function as well.

In preparation for removing the PositiveExponentialManifold from colmap.

Example:

In [1]: import pycolmap

In [2]: sim3 = pycolmap.Sim3d()

In [3]: sim3
Out[3]: Sim3d(scale=1, rotation_xyzw=[0, 0, 0, 1], translation=[0, 0, 0])

In [4]: sim3.scale = 2.0

In [5]: sim3
Out[5]: Sim3d(scale=2, rotation_xyzw=[0, 0, 0, 1], translation=[0, 0, 0])

In [6]: sim3.log_scale
Out[6]: array(0.69314718)

In [7]: sim3.log_scale = -1.0

In [8]: sim3
Out[8]: Sim3d(scale=0.367879, rotation_xyzw=[0, 0, 0, 1], translation=[0, 0, 0])

@B1ueber2y B1ueber2y requested review from ahojnnes and sarlinpe July 17, 2025 14:17
This was referenced Aug 5, 2025
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B1ueber2y added a commit that referenced this pull request Aug 5, 2025
@B1ueber2y
Change input in cost function to log scale and remove custom manifold…
9f636ea 
… from colmap. (#3538)

Fixes: #3537
Fixes: #3485

Cherry-picked from #3494 since
there were no consensus on changing the Sim3d structure due to numerical
stability.
@B1ueber2y B1ueber2y closed this Aug 7, 2025
tavislocus pushed a commit to tavislocus/colmap_6dof that referenced this pull request Aug 19, 2025
@B1ueber2y @tavislocus
Change input in cost function to log scale and remove custom manifold…
b8985ad 
… from colmap. (colmap#3538)

Fixes: colmap#3537
Fixes: colmap#3485

Cherry-picked from colmap#3494 since
there were no consensus on changing the Sim3d structure due to numerical
stability.
ahojnnes pushed a commit that referenced this pull request Aug 22, 2025
@B1ueber2y @ahojnnes
Change input in cost function to log scale and remove custom manifold…
cd55537 
… from colmap. (#3538)

Fixes: #3537
Fixes: #3485

Cherry-picked from #3494 since
there were no consensus on changing the Sim3d structure due to numerical
stability.
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@ahojnnes ahojnnes Awaiting requested review from ahojnnes

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