pyc3dtools

This is python package that you can use it to read your c3d file. Actually, this is an C3Dtools.com API.

- I called it MAHSA

The C3Dtools.com is a free web-based biomechanical toolbox. On C3Dtools.com you can :

    - Lower Body Inverse Kinematic - Plug-in Gait Model NEW
    - Convert C3D file to ASCII and create .TRC and .MOT that is compatible with the Opensim
    - Convert Xsens IMU sensors data to .sto to use in Opensim(Opensens)
    - Detect Gait events based on kinematic data
    - Calculate spatiotemporal gait parameters based on kinematic data
    - Apply Butterworth low-pass and high-pass digital filtering
    - Free C3D files repository
    - Trim C3D file   

Install

pip install pyc3dtools

Usage

First of all, create an account (Register) and then log in to your account, you can find the API token on the home page

and then import pyc3dtools package

import pyc3dtools

Finally pass the API token and your file path to the readC3D function as inputs,

c3d =  pyc3dtools.readC3D(TOKEN,'TYPE-2.C3D')

Get data

1.Header section

Number_of_Markers = c3d['Header']['Number_of_Points']
First_Frame = c3d['Header']['first_frame']
Last_Frame = c3d['Header']['last_frame']
Video_Sampling_Rate = c3d['Header']['Video_Frame_Rate']
Number_of_Analog_Channels = c3d['Header']['Analog_number_channel']
Analog_Sample_Rate = c3d['Header']['Analog_Frame_Rate']
Analog_sample_per_video_frame = c3d['Header']['Analog_sample_per_Frame']

2.Marker & Analog Labels

Markers_Label = c3d['Markers Label']
Analog_Label = c3d['Analog Label']

3. Markers

### c3d['Markers'][frame][marker][:3]

p1 = c3d['Markers'][0][0][:3] # Get the position of the first marker (x,y,z) in the first frame 
p2 = c3d['Markers'][100][0][:3] # Get the position of the first marker (x,y,z) in the 100th frame
p3 = c3d['Markers'][100][1][:3] # Get the position of the second marker (x,y,z) in the 100th frame

5. Units and Coordinate System

Units = c3d['Units']
coordinate_System = c3d['Coordinate system'] #[X_SCREEN, Y_SCREEN]

6. ForcePlate Type 2,3,4,5

### c3d['ForcePlate'][Plate Number]['FZ'][Frame][Analog Frame per Video Frame]

Number_Of_Forceplates = len(result['ForcePlate'])
Force = c3d['ForcePlate'][0]['FX'][100] ,c3d['ForcePlate'][0]['FY'][100],c3d['ForcePlate'][0]['FZ'][100] 
Force = c3d['ForcePlate'][0]['FX'][100][10] ,c3d['ForcePlate'][0]['FY'][100][10],c3d['ForcePlate'][0]['FZ'][100][10] 
Corners c3d['ForcePlate'][0]['corners']
Origin = c3d['ForcePlate'][0]['Origin']

### c3d['ForcePlate'][Plate Number]['COP'][Frame][X|Y|Z][Frame][Analog Frame per Video Frame]
Xcop_frame_50_1 = c3d['ForcePlate'][0]['COP'][50][0][1]
Ycop_frame_50_1 = c3d['ForcePlate'][0]['COP'][50][1][1]
Zcop_frame_50_1 = c3d['ForcePlate'][0]['COP'][50][2][1]

Sample

import sys
import pyc3dtools
import matplotlib.pyplot as plt
import numpy as np

TOKEN = "YOUR TOKEN"

result =  pyc3dtools.readC3D(TOKEN,'TYPE-2.C3D')

if result['Status']=='Failed':
  print(f"Failed to Read File... | {result['error']}") 
  sys.exit(0)

print('---------------------------- C3Dtools.Com ----------------------------')
print(f"Header::Number of Markers = {result['Header']['Number_of_Points']}")
print(f"Header::First Frame = {result['Header']['first_frame']}")
print(f"Header::Last Frame = {result['Header']['last_frame']}")
print(f"Header::Video Sampling Rate = {result['Header']['Video_Frame_Rate']}")
print(f"Header::Analog Channels = {result['Header']['Analog_number_channel']}")
print(f"Header:: Analog Sample Rate = {result['Header']['Analog_Frame_Rate']}")
print(f"Header:: Analog sample per video frame = {result['Header']['Analog_sample_per_Frame']}")


print('----------------------------------------------------------------------')
print(f"GP::Markers Label = {result['Markers Label']}")
print(f"GP::Analog Label = {result['Analog Label']}")
print('----------------------------------------------------------------------')
print(f"Markers:: Frame->0 , {result['Markers Label'][0]}  = {result['Markers'][0][0][:3]}")
print(f"Markers:: Frame->100 , {result['Markers Label'][0]}  = {result['Markers'][100][0][:3]}")
print(f"Markers:: Frame->150 , {result['Markers Label'][1]}  = {result['Markers'][150][1][:3]}")
print(f"Markers:: Units = {result['Units']}")
print(f"coordinate System [X_SCREEN, Y_SCREEN] = {result['Coordinate system']}")
print('----------------------------------------------------------------------')
print(f"Number Of Forceplates = {len(result['ForcePlate'])}")
#print(f"First plate:: FX, FY, FZ :: Frame->100 = ({result['ForcePlate'][0]['FX'][100] ,result['ForcePlate'][0]['FY'][100],result['ForcePlate'][0]['FZ'][100] })") # Analog sample per video frame is equal 20 
print(f"First plate:: FX, FY, FZ :: Frame->100 :: Analog Sample 10 = {result['ForcePlate'][0]['FX'][100][10] ,result['ForcePlate'][0]['FY'][100][10],result['ForcePlate'][0]['FZ'][100][10] }") # Analog sample per video frame is equal 20 
print(f"First plate:: Corners = {result['ForcePlate'][0]['corners']}")
print(f"First plate:: Origin = {result['ForcePlate'][0]['Origin']}")
print(f"First plate:: COP :: X,Y,Z :: Frame->50 :: Analog Sample 1 = {result['ForcePlate'][0]['COP'][50][0][1],result['ForcePlate'][0]['COP'][50][1][1],result['ForcePlate'][0]['COP'][50][2][1]}") # Analog sample per video frame is equal 20 



#plot data
Marker1 = result['Markers'][:,1,:3]

FZ = np.array(result['ForcePlate'][0]['FZ'])
FZ = FZ.flatten()


COP = result['ForcePlate'][0]['COP'][:,:,:]
COP_X = COP[:,0,:]
COP_Y = COP[:,1,:]
COP_X = COP_X.flatten()
COP_Y = COP_Y.flatten()


Vec_GRF = result['ForcePlate'][0]['GRF_VECTOR'][:,:,:]
Vec_GRF_X = Vec_GRF[:,0,:]
Vec_GRF_Y = Vec_GRF[:,1,:]
Vec_GRF_Z = Vec_GRF[:,2,:]
Vec_GRF_X = Vec_GRF_X.flatten()
Vec_GRF_Y = Vec_GRF_Y.flatten()
Vec_GRF_Z = Vec_GRF_Z.flatten()


fig = plt.figure()
axs = fig.subplots(2, 2)
axs[0, 0].plot(Marker1[:,0], color='r', label='X')
axs[0, 0].plot(Marker1[:,1], color='g', label='Y')
axs[0, 0].plot(Marker1[:,2], color='b', label='Z')
axs[0, 0].set_title('Marker Position')
axs[0, 1].plot(FZ, 'tab:orange')
axs[0, 1].set_title('GRF Z')
axs[1, 0].plot(COP_X, color='g', label='copX')
axs[1, 0].plot(COP_Y, color='b', label='copY')
axs[1, 0].set_title('COP')
axs[1, 1].plot(Vec_GRF_X, color='g', label='GRFX')
axs[1, 1].plot(Vec_GRF_Y, color='b', label='GRFY')
axs[1, 1].plot(Vec_GRF_Z, color='r', label='GRFZ')
axs[1, 1].set_title('GRF vector')




NumFrames = result['Header']['last_frame'] - result['Header']['first_frame']

Forceplates = result['ForcePlate']
cop_data = []
grf_vector = []
corners = []
for fp in Forceplates:  
  #COP 
  cop_data.append(fp['COP'])
  #GRF
  grf_vector.append(fp['GRF_VECTOR'])
  #Corners
  for c in range(4):    
    corners.extend(fp['corners'])



# COP & GRF
main_cop_data =[]
main_grf_data =[]

for i in range(NumFrames):   
  for fp in range(len(Forceplates)):
    main_cop_data.append([cop_data[fp][i,0,0] , cop_data[fp][i,1,0]])
    main_grf_data.append([grf_vector[fp][i,0,0] , grf_vector[fp][i,1,0], grf_vector[fp][i,2,0]])  



# Get Analog data
Analog_Label = result['Analog Label']
Analog_Data = result['Analog']

ch0 = Analog_Data[:,:,0]
ch1 = Analog_Data[:,:,1]
ch2 = Analog_Data[:,:,2]




plt.show()

print('OK')

Export .mot and .trc

If you need to convert your c3d file to compatible files for OpenSim software you can use getTRCMot function. This function returns all c3d file data and also write .mot and .trc file in a directory

import pyc3dtools
TOKEN = "YOUR_TOKEN"
#result =  pyc3dtools.getTRCMot(TOKEN,'Input C3D File','Destination directory')
result =  pyc3dtools.getTRCMot(TOKEN,'TYPE-2.C3D','./exportData')

Export .mot and .trc Sample code

import pyc3dtools
TOKEN = "YOUR_TOKEN"
result =  pyc3dtools.getTRCMot(TOKEN,'TYPE-2.C3D','./exportData')
if result['Status'] == 'Success':
    print('Done.')

Inverse Kinematic : Plug-in Gait

By this API can compute the joint's kinematics. Just pass a static trial, a dynamic trial and anthropometry data of your subject.

import pyc3dtools
import matplotlib.pyplot as plt
import numpy as np

TOKEN = "YOUR TOKEN"

Anthropometry = [('Left_Leg_Length',800), # mm
                  ('Right_Leg_Length',800),
                  ('Knee_Width',100),
                  ('Ankle_Width',90),
                  ('Marker_Radius',14)]


Markers_label = [('LASI','LASI'), # (Fixed label , your label in c3d file)
                 ('RASI','RASI'), # (Fixed label , your label in c3d file)
                 ('LPSI','LPSI'), # (Fixed label , your label in c3d file)
                 ('RPSI','RPSI'), # (Fixed label , your label in c3d file)
                 #('SACR','SACR'), # (Fixed label , your label in c3d file) - Optional
                 ('LTHI','LTHI'), # (Fixed label , your label in c3d file)
                 ('RTHI','RTHI'), # (Fixed label , your label in c3d file)
                 ('LKNE','LKNE'), # (Fixed label , your label in c3d file)
                 ('RKNE','RKNE'), # (Fixed label , your label in c3d file)
                 ('LTIB','LTIB'), # (Fixed label , your label in c3d file)
                 ('RTIB','RTIB'), # (Fixed label , your label in c3d file)
                 ('LANK','LANK'), # (Fixed label , your label in c3d file)
                 ('RANK','RANK'), # (Fixed label , your label in c3d file)
                 ('LHEE','LHEE'), # (Fixed label , your label in c3d file)
                 ('RHEE','RHEE'), # (Fixed label , your label in c3d file)
                 ('LTOE','LTOE'), # (Fixed label , your label in c3d file)
                 ('RTOE','RTOE')] # (Fixed label , your label in c3d file)


#pyc3dtools.IKPiG(TOKEN, Static Trial,Dynamic Trial, Markers_label,Anthropometry,[start Frame, end Frame] *Optional)
result =  pyc3dtools.IKPiG(TOKEN,'Cal 01.C3D','Walking 01.C3D',Markers_label,Anthropometry)



if result['Status'] == 'Success':
    print('Done.')
    t = np.arange(0,len(result['IK_Result'][0]['angle']))  

    fig, axs = plt.subplots(3, 2)
    # HIP Joint
    LHIP = next((obj for obj in result['IK_Result'] if obj['name'] == 'LHIP'),  None)
    RHIP = next((obj for obj in result['IK_Result'] if obj['name'] == 'RHIP'),  None)
    LHIP_angle_x = [item[0] for item in LHIP['angle']]
    LHIP_angle_y = [item[1] for item in LHIP['angle']]
    LHIP_angle_z = [item[2] for item in LHIP['angle']]
    axs[0,0].plot(t,LHIP_angle_x,t,LHIP_angle_y,t,LHIP_angle_z)
    axs[0,0].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[0,0].set_ylabel('Left HIP')

    RHIP_angle_x = [item[0] for item in RHIP['angle']]
    RHIP_angle_y = [item[1] for item in RHIP['angle']]
    RHIP_angle_z = [item[2] for item in RHIP['angle']]     
    axs[0,1].plot(t,RHIP_angle_x,t,RHIP_angle_y,t,RHIP_angle_z)
    axs[0,1].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[0,1].set_ylabel('Right HIP')

    # KNEE Joint
    LKNEE = next((obj for obj in result['IK_Result'] if obj['name'] == 'LKNEE'),  None)
    RKNEE = next((obj for obj in result['IK_Result'] if obj['name'] == 'RKNEE'),  None)
    LKNEE_angle_x = [item[0] for item in LKNEE['angle']]
    LKNEE_angle_y = [item[1] for item in LKNEE['angle']]
    LKNEE_angle_z = [item[2] for item in LKNEE['angle']]
    axs[1,0].plot(t,LKNEE_angle_x,t,LKNEE_angle_y,t,LKNEE_angle_z)
    axs[1,0].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[1,0].set_ylabel('Left Knee')

    RKNEE_angle_x = [item[0] for item in RKNEE['angle']]
    RKNEE_angle_y = [item[1] for item in RKNEE['angle']]
    RKNEE_angle_z = [item[2] for item in RKNEE['angle']] 
    axs[1,1].plot(t,RKNEE_angle_x,t,RKNEE_angle_y,t,RKNEE_angle_z)
    axs[1,1].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[1,1].set_ylabel('Right Knee')


    # ANKLe Joint
    LANK = next((obj for obj in result['IK_Result'] if obj['name'] == 'LANK'),  None)
    RANK = next((obj for obj in result['IK_Result'] if obj['name'] == 'RANK'),  None)
    LANK_angle_x = [item[0] for item in LANK['angle']]
    LANK_angle_y = [item[1] for item in LANK['angle']]
    LANK_angle_z = [item[2] for item in LANK['angle']]
    axs[2,0].plot(t,LANK_angle_x,t,LANK_angle_y,t,LANK_angle_z)
    axs[2,0].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[2,0].set_ylabel('Left Ankle')

    RANK_angle_x = [item[0] for item in RANK['angle']]
    RANK_angle_y = [item[1] for item in RANK['angle']]
    RANK_angle_z = [item[2] for item in RANK['angle']] 
    axs[2,1].plot(t,RANK_angle_x,t,RANK_angle_y,t,RANK_angle_z)
    axs[2,1].legend(['Flex/Ext','Abd/Add','Ex/Int Rotation'])
    axs[2,1].set_ylabel('right Ankle')
   

    plt.show()    

Inverse Kinematic Sample Output

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