What is the unit of tag_size?

[mzahana]

@koide3 Thanks for this useful package.

What is the unit of the tag_size ? If I want to generate tag with 1 meter edge length, what would be the tag_size value?
Thank you.

[koide3]

tag_size in generate.py is the texture size. To change the tag size, you need to change <size> in model.sdf.

gazebo_apriltag/template/model.sdf

Line 9 in 872685a

<size>1.0 1.0 0.01</size>

In this case, real tag size (for pose estimation) will be 0.8 because each tag occupies 80% of the rectangle in width.

[mzahana]

Thanks @koide3 . So, what are the required steps to, for example, generate a tag with physical size of 1 meter?
In this case, the size which will be passed to the tag detector is 1.0.

[koide3]

The steps would be like: 1) change <size> in template/model.sdf to 1 / 0.8 = 1.25, 2) run generate.py, 3) you can find generated models in models

[qlibp]

@koide3 Thanks for the script!
I have another question on how to set the "correct" tag_size. If the physical size of tag is 1mx1m, what's the recommended tag_size? 1024x1024? What if the physical size is 3m? 1024 * 3 x 1024 * 3?

[koide3]

Usually you don't need to change tag_size (texture size) unless you see some blur on rendering results. 1024x1024 is sufficiently large for most situations. If you want to change the "physical size" of tags, modify the <size> tag in model.sdf.

gazebo_apriltag/template/model.sdf

Line 9 in 872685a

<size>1.0 1.0 0.01</size>

[qlibp]

Usually you don't need to change tag_size (texture size) unless you see some blur on rendering results. 1024x1024 is sufficiently large for most situations. If you want to change the "physical size" of tags, modify the <size> tag in model.sdf.

gazebo_apriltag/template/model.sdf

Line 9 in 872685a

<size>1.0 1.0 0.01</size>

Thanks for your experience! As I try to generate a apriltag board, I need to try some texture size to see if it will blur with 1024x1024.