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diff --git a/docs/user_guide/aruco_markers/markers_scene_description.md b/docs/user_guide/aruco_markers/markers_scene_description.md new file mode 100644 index 0000000..9938f23 --- /dev/null +++ b/docs/user_guide/aruco_markers/markers_scene_description.md @@ -0,0 +1,117 @@ +Markers scene description +========================= + +The ArGaze toolkit provides ArUcoScene class to describe where ArUco markers are placed into a 3D model. + + + +ArUco scene is useful to: + +* filter markers that belongs to this predefined scene, +* check the consistency of detected markers according the place where each marker is expected to be, +* estimate the pose of the scene from the pose of detected markers. + +ArUco scene description uses common OBJ file format that can be exported from most 3D editors. Notice that plane normals (vn) needs to be exported. + +``` obj +o DICT_APRILTAG_16h5#0_Marker +v -3.004536 0.022876 2.995370 +v 2.995335 -0.015498 3.004618 +v -2.995335 0.015498 -3.004618 +v 3.004536 -0.022876 -2.995370 +vn 0.0064 1.0000 -0.0012 +s off +f 1//1 2//1 4//1 3//1 +o DICT_APRILTAG_16h5#1_Marker +v -33.799068 46.450645 -32.200436 +v -27.852505 47.243549 -32.102116 +v -34.593925 52.396473 -32.076626 +v -28.647360 53.189377 -31.978306 +vn -0.0135 -0.0226 0.9997 +s off +f 5//2 6//2 8//2 7//2 +... +``` + +ArUco scene description can also be written in a JSON file format. + +``` json +{ + "dictionary": "DICT_ARUCO_ORIGINAL", + "marker_size": 1, + "places": { + "0": { + "translation": [0, 0, 0], + "rotation": [0, 0, 0] + }, + "1": { + "translation": [10, 10, 0], + "rotation": [0, 0, 0] + }, + "2": { + "translation": [0, 10, 0], + "rotation": [0, 0, 0] + } + } +} +``` + +Here is a sample of code to show the loading of an ArUcoScene OBJ file description: + +``` python +from argaze.ArUcoMarkers import ArUcoScene + +# Create an ArUco scene from a OBJ file description +aruco_scene = ArUcoScene.ArUcoScene.from_obj('./markers.obj') + +# Print loaded marker places +for place_id, place in aruco_scene.places.items(): + + print(f'place {place_id} for marker: ', place.marker.identifier) + print(f'place {place_id} translation: ', place.translation) + print(f'place {place_id} rotation: ', place.rotation) +``` + +## Markers filtering + +Considering markers are detected, here is how to filter them to consider only those which belongs to the scene: + +``` python +scene_markers, remaining_markers = aruco_scene.filter_markers(aruco_detector.detected_markers) +``` + +## Marker poses consistency + +Then, scene markers poses can be validated by verifying their spatial consistency considering angle and distance tolerance. This is particularly useful to discard ambiguous marker pose estimations when markers are parallel to camera plane (see [issue on OpenCV Contribution repository](https://github.com/opencv/opencv_contrib/issues/3190#issuecomment-1181970839)). + +``` python +# Check scene markers consistency with 10° angle tolerance and 1 cm distance tolerance +consistent_markers, unconsistent_markers, unconsistencies = aruco_scene.check_markers_consistency(scene_markers, 10, 1) +``` + +## Scene pose estimation + +Several approaches are available to perform ArUco scene pose estimation from markers belonging to the scene. + +The first approach considers that scene pose can be estimated **from a single marker pose**: + +``` python +# Let's select one consistent scene marker +marker_id, marker = consistent_markers.popitem() + +# Estimate scene pose from a single marker +tvec, rmat = self.aruco_scene.estimate_pose_from_single_marker(marker) +``` + +The second approach considers that scene pose can be estimated **by averaging several marker poses**: + +``` python +# Estimate scene pose from all consistent scene markers +tvec, rmat = self.aruco_scene.estimate_pose_from_markers(consistent_markers) +``` + +The third approach is only available when ArUco markers are placed in such a configuration that is possible to **define orthogonal axis**: + +``` python +tvec, rmat = self.aruco_scene.estimate_pose_from_axis_markers(origin_marker, horizontal_axis_marker, vertical_axis_marker) +``` |