I’m trying to use the April-Tag texture in a scene and had some issues because my April Tag detectors didn’t agree with the ground truth data I got from Isaac. I used the demo-markers from Assets/Isaac/4.2/Isaac/Samples/ROS/Scenario/april_tag.usd and finally noticed that all markers are rotated clockwise by 90 deg.
A mere rotation of the object does not help because this would also rotate the tf-frame. The orientation of the tag in the local frame of the prim has to change.
I created a new marker that fixes the issue by scaling the cube in z to 0.0001 instead of x. I then published the image (and the tag on /tf) and ran apriltag_ros. Now the frame published by IsaacSim and apriltag_ros are aligned.
This is the usda of my marker: I also added a back cover to make sure that the tag on the back side is not visible so make sure that I don’t put the marker on a wall in the wrong direction and run into new weird effects of a flipped coordinate system.
If you want to repeat the experiment with apriltag_ros, make sure to set the marker size of 0.8.
