Feature Matching Issue

[Sean H]

I'm new to Colmap, and am using the COLMAP-CL version since I don't have a Nvidia card. I am using a small sample set of images for my first project, and all seems to be going well until the feature mapping stage. At this point, the message "Matching Block [1/1, 1/1]" appears. The program continues running, but no progress is made. I'm at a loss as to what the issue could be. A screenshot of the situation I keep running into is attached below.

Any help would be much appreciated!

[Wayne Cochran]

Did you look at the features using after performing feature extraction via Processing -> Database management menu?

You can view the images with the features overlaid as red circles. How many features are extracted?

The features must already be in the database (i.e. feature extraction already done) since the images are skipped. 

This is just a sanity check.

Next you can reduce the block size (I think the default is 50) for feature matching -- this will split the matching

into smaller chunks. See if that helps. How much memory does you GPU and CPU have?

BTW, you actually don't need an nVidia card if you are only performing a sparse reconstruction (CUDA not needed / it will use shader code to perform GPU work).

[Sean H]

It seems that the feature extraction may already be done, as when I view the images with the Processing -> Database management menu the features are shown as red circles. The menu says that over 131,000 features have been found from the 14 images in the data set. But unfortunately, even with block size reduced to 25, the problem I detailed in my first email persists. 

My GPU has 4864 MB available and my CPU has 9.79 GB of RAM available.

I'm not sure if sparse reconstruction will fit my needs; would it be able to generate 3D objects which I could then 3D print?

Thanks for the help, and I appreciated any further suggestions you may have.

I've attached some more screenshots below in case they reveal any important information.

[Wayne Cochran]

Since you only have 14 images you would have to set the block size to a value less than 14 to split up the matching processes,

[Sean H]

Thanks for the suggestion, that makes sense. However, even with block sizes of 10 and 3, the issue doesn't change.

[Sean H]

Update: I seem to have made a bit of progress! Once I unchecked "use_gpu", I was able to get a sparse reconstruction of the model.

However, once I moved on to the stereo phase of dense reconstruction, Colmap immediately crashed (it happened right after I hit the "stereo" button). The following message was displayed in my command line:

QObject::~QObject: Timers cannot be stopped from another thread

I did a bit of researching and found that the problem may be related to a lack of GPU memory, although there are no definitive answers out there. Let me know if you have any thoughts as to what the problem may be.

[abir ben soltane]

Good morning, I want to know where I can find the block size so that I can reduce it ,please.

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[Revisionarian]

In the GUI, the block size is set under the "Processing : Feature matching" menu. It's the first parameter in the "Exhaustive" tab.

In the CLI, it's the "colmap exhaustive_matcher --ExhaustiveMatching.block_size" parameter.