Halcon/3D object normals

Q&A
1

Hi everyone,
I’m using Mech-eye Pro M with Halcon. My question is related to surface 3D object normals. As you can see in the code, I can extract the data with no issues, but when I try to use the extracted normals their orientation seems off as they all point almost to the same direction. The visualization using Halcon Object Model Inspect shows the normals pointing in the expected directions, but the x, y, z, vector tuples don’t seem right. I’m using the box 3D object to visualize the normals.

xyz_to_object_model_3d (ImageReducedX, ImageReducedY, ImageReducedZ, ObjectModel3DScene)
smooth_object_model_3d (ObjectModel3DScene, ‘mls’, ‘mls_kNN’, 2000, SmoothObjectModel3D)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_coord_x’, GenParamValue)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_coord_y’, GenParamValueY)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_coord_z’, GenParamValueZ)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_normal_x’, NormalPointX)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_normal_y’, NormalPointY)
get_object_model_3d_params (SmoothObjectModel3D, ‘point_normal_z’, NormalPointZ)
for i:=0 to (Length-1) by 1
RobotPose[0] := GenParamValue[i]
RobotPose[1] := GenParamValueY[i]
RobotPose[2] := GenParamValueZ[i]
normal_x := NormalPointX[i]
normal_y := NormalPointY[i]
normal_z := NormalPointZ[i]

tuple_acos (normal_x, u)
tuple_acos (normal_y, v)
tuple_acos (normal_z, w)
tuple_deg (u, U)
tuple_deg (v, V)
tuple_deg (w, W)
create_pose (0, 0, 0, U, V, W, 'Rp+T', 'abg', 'point', PoseNormal)
RobotPose[3] := U
RobotPose[4] := V
RobotPose[5] := W
tuple_string(RobotPose,'-10.3f',stringTuple)
RC7_command := stringTuple[0] + ',' + stringTuple[1] +  ',' +stringTuple[2] + ',' + stringTuple[3] + ',' + stringTuple[4] +  ',' +stringTuple[5]
fwrite_string (FileHandle, RC7_command)
fnew_line (FileHandle)

create_pose(GenParamValue[i],GenParamValueY[i],GenParamValueZ[i], U, V, W, 'Rp+T', 'abg', 'point', Pose1)
gen_box_object_model_3d (Pose1, 1, 3, 6, ObjectModel3D)
visualize_object_model_3d(WindowHandle3d, [ObjectModel3D,SmoothObjectModel3D ], [], [], ['color_1','color_0'], ['white','red'], [], [], [], PoseOut)

endfor

2

Hello, if you need to calculate point cloud normals, you can refer to: Calculating normal vectors using Halcon, and we also provide an example routine for outputting normal point clouds: https://docs.mech-mind.net/en/eye-3d-camera/latest/genicam/obtain-point-cloud-with-normals.html

It seems that your program involves robot pose transformation. If you need to calibrate the extrinsic parameters between the camera and the robot, you can try using the routines we provide: Hand-Eye Calibration.