How to lower keypoint threshold limit

[vik748]

Hi,
I am working with a set of images of ice which are low contrast and low texture.  When I use default settings of 40,000 keypoints, Metashape seems to only be able to detect a few thousand.
Is there a way to lower the keypoint detection threshold so that I can get more keypoints?  Possibly by adding something under Tools -> Preferences -> Advanced -> Tweaks

Thanks in advance.

[vik748]

Here is an example of the keypoints detected, see attachment.

[Alexey Pasumansky]

Hello vik748,

Which Accuracy setting do you use and what is the Tie point limit?

Also please specify the image dimensions.

[vik748]

Alexey,
The settings are:
Accuracy: Highest
Key point limit: 60,000
Tie point limit: 100,000

This particular image is from a drone and is 5472 x 3078.  I also use similar images from go pro camera which are 4000x3000.

[Alexey Pasumansky]

Hello vik748,

Then the images may be just too noisy (or do not have sufficient overlap), if there are too few tie points detected even with Highest accuracy.

Note that tie point limit value higher than key point limit would not have any effect - it is equal to tie point limit = key point limit (or just tie point limit set to zero value).

[vik748]

Alexey,
I am only thinking about the detected keypoints and not tie points at this time. The white points are all the detected key points and as you can see they are way less than 60K.
Most feature detectors like ORB and SIFT allow you to choose a minimum threshold to be called a keypoint. Is there any way I can try to reduce that kind of threshold below the default values in Metashape.
Since I am looking at ice, my images are always like this and can't do much while capturing them.
Thanks,
Vik

[Alexey Pasumansky]

Hello Vik,

Key points are not shown in the Photo view mode. You only see tie points (blue - valid, i.e. used tie points, and white - invalid, i.e. unused).

The number of detected key points per image is shown in the processing log (in the Console pane) during the matching operation.

[vik748]

Alexey,
Thanks for that information.  I stand corrected, from the logs I see that Metashape is indeed detecting the required number of points. 

Are there any other tips / tweaks that could be used to improve the matching process?  I have uploaded a few test images to https://drive.google.com/file/d/1O6ib_RFUzzZssZxQyrINJEE5gMDDVkgl/view?usp=sharing

As you can see from the images, visually we can easily track between the images, however Metashape is not able to match the keypoints well.  Are there any settings / tweaks that could help Metashape with the matching?

Thanks for all the help,
Vik