10.2. Interconnecting the points#

In the previous section, we learned how to show markers in the Player:

import kineticstoolkit.lab as ktk

# Download and read markers from a sample C3D file
filename = ktk.doc.download("kinematics_tennis_serve_2players.c3d")
markers = ktk.read_c3d(filename)["Points"]
p = ktk.Player(markers, up="z", anterior="-y")

10.2.1. Interconnection dictionary#

To ease the visualization, it is often practical to interconnect markers with lines. We create these links as a dictionary of this form:

Player custom viewpoint

Fig. 10.2 Interconnection dictionary.#

Let’s see the list of point names we have in this example:

markers.data.keys()

dict_keys(['Derrick:C7', 'Derrick:CLAV', 'Derrick:LANK', 'Derrick:LASI', 'Derrick:LBHD', 'Derrick:LELB', 'Derrick:LFHD', 'Derrick:LFIN', 'Derrick:LFRM', 'Derrick:LHEE', 'Derrick:LKNE', 'Derrick:LPSI', 'Derrick:LSHO', 'Derrick:LTHI', 'Derrick:LTIB', 'Derrick:LTOE', 'Derrick:LUPA', 'Derrick:LWRA', 'Derrick:LWRB', 'Derrick:RANK', 'Derrick:RASI', 'Derrick:RBAK', 'Derrick:RBHD', 'Derrick:RELB', 'Derrick:RFHD', 'Derrick:RFIN', 'Derrick:RFRM', 'Derrick:RHEE', 'Derrick:RKNE', 'Derrick:RPSI', 'Derrick:RSHO', 'Derrick:RTHI', 'Derrick:RTIB', 'Derrick:RTOE', 'Derrick:RUPA', 'Derrick:RWRA', 'Derrick:RWRB', 'Derrick:STRN', 'Derrick:T10', 'Viktor:C7', 'Viktor:CLAV', 'Viktor:LANK', 'Viktor:LASI', 'Viktor:LBHD', 'Viktor:LELB', 'Viktor:LFHD', 'Viktor:LFIN', 'Viktor:LFRM', 'Viktor:LHEE', 'Viktor:LKNE', 'Viktor:LPSI', 'Viktor:LSHO', 'Viktor:LTHI', 'Viktor:LTIB', 'Viktor:LTOE', 'Viktor:LUPA', 'Viktor:LWRA', 'Viktor:LWRB', 'Viktor:RANK', 'Viktor:RASI', 'Viktor:RBAK', 'Viktor:RBHD', 'Viktor:RELB', 'Viktor:RFHD', 'Viktor:RFIN', 'Viktor:RFRM', 'Viktor:RHEE', 'Viktor:RKNE', 'Viktor:RPSI', 'Viktor:RSHO', 'Viktor:RTHI', 'Viktor:RTIB', 'Viktor:RTOE', 'Viktor:RUPA', 'Viktor:RWRA', 'Viktor:RWRB', 'Viktor:STRN', 'Viktor:T10'])

To create interconnections for Derrick’s left lower limb, we would need to connect these points:

  • Foot: draw a line that starts at Derrick:LTOE, then Derrick:LHEE, then Derrick:LANK, then back to Derrick:LTOE.

  • Shank and thigh: draw a line that starts at Derrick:LANK, then Derrick:LKNE, then Derrick:LASI. Also, draw a line between Derrick:LKNE and Derrick:LPSI.

This translates to this code:

interconnections = dict()

interconnections["LLowerLimb"] = {
    "Color": (0, 0.5, 1),  # In (R,G,B) format (here, greenish blue)
    "Links": [  # List of lines that span lists of markers
        ["Derrick:LTOE", "Derrick:LHEE", "Derrick:LANK", "Derrick:LTOE"],
        ["Derrick:LANK", "Derrick:LKNE", "Derrick:LASI"],
        ["Derrick:LKNE", "Derrick:LPSI"],
    ],
}

Let’s see the result:

p.set_interconnections(interconnections)

We continue with Derrick’s other segments:

interconnections["RLowerLimb"] = {
    "Color": (0, 0.5, 1),
    "Links": [
        ["Derrick:RTOE", "Derrick:RHEE", "Derrick:RANK", "Derrick:RTOE"],
        ["Derrick:RANK", "Derrick:RKNE", "Derrick:RASI"],
        ["Derrick:RKNE", "Derrick:RPSI"],
    ],
}

interconnections["LUpperLimb"] = {
    "Color": (0, 0.5, 1),
    "Links": [
        ["Derrick:LSHO", "Derrick:LELB", "Derrick:LWRA", "Derrick:LFIN"],
        ["Derrick:LELB", "Derrick:LWRB", "Derrick:LFIN"],
        ["Derrick:LWRA", "Derrick:LWRB"],
    ],
}

interconnections["RUpperLimb"] = {
    "Color": (1, 0.5, 0),
    "Links": [
        ["Derrick:RSHO", "Derrick:RELB", "Derrick:RWRA", "Derrick:RFIN"],
        ["Derrick:RELB", "Derrick:RWRB", "Derrick:RFIN"],
        ["Derrick:RWRA", "Derrick:RWRB"],
    ],
}

interconnections["Head"] = {
    "Color": (1, 0.5, 1),
    "Links": [
        ["Derrick:C7", "Derrick:LFHD", "Derrick:RFHD", "Derrick:C7"],
        ["Derrick:C7", "Derrick:LBHD", "Derrick:RBHD", "Derrick:C7"],
        ["Derrick:LBHD", "Derrick:LFHD"],
        ["Derrick:RBHD", "Derrick:RFHD"],
    ],
}

interconnections["TrunkPelvis"] = {
    "Color": (0.5, 1, 0.5),
    "Links": [
        ["Derrick:LASI", "Derrick:STRN", "Derrick:RASI"],
        ["Derrick:STRN", "Derrick:CLAV"],
        ["Derrick:LPSI", "Derrick:T10", "Derrick:RPSI"],
        ["Derrick:T10", "Derrick:C7"],
        ["Derrick:LASI", "Derrick:LSHO", "Derrick:LPSI"],
        ["Derrick:RASI", "Derrick:RSHO", "Derrick:RPSI"],
        [
            "Derrick:LPSI",
            "Derrick:LASI",
            "Derrick:RASI",
            "Derrick:RPSI",
            "Derrick:LPSI",
        ],
        [
            "Derrick:LSHO",
            "Derrick:CLAV",
            "Derrick:RSHO",
            "Derrick:C7",
            "Derrick:LSHO",
        ],
    ],
}

p.set_interconnections(interconnections)

10.2.2. Wildcards#

We could do the same for Viktor, by replacing every occurrence of “Derrick:” by “Viktor:” in interconnections. However, a more generic way is to use wildcards (*). A wildcard mean “assign any name in place of *”. According to the naming scheme, we may choose to use wildcards as a prefix or as a suffix. Here, we use it as a prefix:

interconnections = dict()  # Will contain all segment definitions

interconnections["LLowerLimb"] = {
    "Color": (0, 0.5, 1),  # In RGB format (here, greenish blue)
    "Links": [  # List of lines that span lists of markers
        ["*LTOE", "*LHEE", "*LANK", "*LTOE"],
        ["*LANK", "*LKNE", "*LASI"],
        ["*LKNE", "*LPSI"],
    ],
}

interconnections["RLowerLimb"] = {
    "Color": (0, 0.5, 1),
    "Links": [
        ["*RTOE", "*RHEE", "*RANK", "*RTOE"],
        ["*RANK", "*RKNE", "*RASI"],
        ["*RKNE", "*RPSI"],
    ],
}

interconnections["LUpperLimb"] = {
    "Color": (0, 0.5, 1),
    "Links": [
        ["*LSHO", "*LELB", "*LWRA", "*LFIN"],
        ["*LELB", "*LWRB", "*LFIN"],
        ["*LWRA", "*LWRB"],
    ],
}

interconnections["RUpperLimb"] = {
    "Color": (1, 0.5, 0),
    "Links": [
        ["*RSHO", "*RELB", "*RWRA", "*RFIN"],
        ["*RELB", "*RWRB", "*RFIN"],
        ["*RWRA", "*RWRB"],
    ],
}

interconnections["Head"] = {
    "Color": (1, 0.5, 1),
    "Links": [
        ["*C7", "*LFHD", "*RFHD", "*C7"],
        ["*C7", "*LBHD", "*RBHD", "*C7"],
        ["*LBHD", "*LFHD"],
        ["*RBHD", "*RFHD"],
    ],
}

interconnections["TrunkPelvis"] = {
    "Color": (0.5, 1, 0.5),
    "Links": [
        ["*LASI", "*STRN", "*RASI"],
        ["*STRN", "*CLAV"],
        ["*LPSI", "*T10", "*RPSI"],
        ["*T10", "*C7"],
        ["*LASI", "*LSHO", "*LPSI"],
        ["*RASI", "*RSHO", "*RPSI"],
        ["*LPSI", "*LASI", "*RASI", "*RPSI", "*LPSI"],
        ["*LSHO", "*CLAV", "*RSHO", "*C7", "*LSHO"],
    ],
}

p.set_interconnections(interconnections)