RESOLVED: Reading the values from a noise TOP - double rows and cols

I wanted to read out the values of a noise TOP.
I have added a .tox file.
The noise TOP has 10 rows and 10 columns.
If I extract the values of each row individually with a TOP to CHOP and having it read a row with the V Start from 0 to 0.5 (rows 1 to 6) it all works fine.
But with V Start = 0.6 (should be row 7) it shows the same values as row 6.
In my example I named it ‘row_6_again’.
I then have to use V Start = 0.7 to 1 to get the rows 7 to 10.

Same happens similarly when I extract the columns. Col 6 is twice.

When I extract the ‘Full Image’ and have it shown as ‘Single Channel Set’ and then cut it up into the individual rows it works fine.
Does anyone have a solution for this.
Thanks Markus
20230522_reading_noise_values_BUG.tox (10.0 KB)

Hey @knoedel

Thanks for the report.

This is logged for a developer to look into it.


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The values 0.1 0.2 etc are landing directly on the boundary between pixels, since this image is 10 pixels wide. It’s undefined if it’ll end up sampling the left or the right of the coordinate you are choosing. You should be using either pixel indices, or sampling somewhere inside of the pixel (0.05, 0.15 etc.).
For example on my GPU, I don’t get the same results as you, and I see a different column sampled for each coordinate you are specifying.

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Hi Malcolm.
I understand. It is a ‘sub pixel problem’ It would have been convenient to use me.digit to read the corresponding lines.
How would I read the pixel indices?

You can change the unit menu (the small menu on the right of the Crop U/V sliders, into pixel units. Then you can select your pixels more directly.

Thank you @malcolm.
That did it.