[quentin]

Hello @Hugo,

To clarify, we have to add the UncoupledConstraintCorrection to correct the free calculation (without constraints), don’t we ? But you say that this correction needs to an implicit scheme, or in other words not RungeKutta, is it correct ?

Thanks for your help

Q

[quentin]

Hi @Hugo,

Thanks for the help ! The sum that you talk about, is it a temporal sum or just a sum of all the forces at the precise time ?

Thanks for the help

[quentin]

To resolve my problem, I juste have to see the value of the force really applied on each point. Is it possible to access it with the indices or an option like that ?

[quentin]

Hi everyone,

I found in the oxygen that the totalForce is the sum of all the forces applied at each point : https://www.sofa-framework.org/api/master/sofa/html/classsofa_1_1component_1_1forcefield_1_1_constant_force_field.html#a7f45cdbc837c9ac22f44763806e0823f

That’s why we have the deformation which is not following the force signal. The problem is when I use the force attribute I have the value of the force applied on each point and not divided by the number of points. Is there another attribute that I didn’t find to apply a force which will not be summed in time to all the points (and not to each point) ?

[quentin]

Yes I mean it, I see the force arrows as before but I still have the problem of the displacement which isn’t following the force signal. The situation hasn’t changed.

[quentin]

Hi Hugo,

Thanks for your help ! I tried to directly update the data as you said. The vector is a column one therefore I can access the value like that :
print(self.forceField.findData('totalForce').value[0][1])

Nevertheless, it is impossible to edit it directly, it seems that I have to edit all the vector.

This isn’t working :
self.forceField.findData('totalForce').value[0][1] = force

This is working :
self.forceField.findData('totalForce').value = [0, force, 0]

[quentin]

Hi Jean-Nicolas,

Thanks for your help ! I changed the string I sent to the totalForce in a vector like that :
self.forceField.findData('totalForce').value = [0, force, 0]

I display the new totalForce on the terminal like that :
print(self.forceField.findData('totalForce').value)

I have the good value as I want with my negative sinus square (I see the force arrow s on the GUI) but the deformation doesn’t seem to follow the force signal. In fact, I have a tube with a spring in the middle and I try to compress it. I block the bottom and apply the force on the top part. The problem is that the force is a sinus and the deformation continues to increase permanently (so a line). Here you can see the force applied in the vector lines and the position of the point just under each vector.

[[0.0, -0.0, 0.0]]
1000.0
[[0.0, -21067.05423352457, 0.0]]
998.210218854
[[0.0, -81309.41177357652, 0.0]]
996.376814199
[[0.0, -172266.21253047822, 0.0]]
993.959163958
[[0.0, -281162.84414120595, 0.0]]
991.292846044
[[0.0, -392705.09831248416, 0.0]]
987.782535008
[[0.0, -491227.196924607, 0.0]]
983.855256778
[[0.0, -562892.0040131591, 0.0]]
979.023956496
[[0.0, -597634.4103943433, 0.0]]
973.678487509
[[0.0, -590574.9483385893, 0.0]]
967.601948838
[[0.0, -542705.0983124842, 0.0]]
961.047161738
[[0.0, -460748.03849369887, 0.0]]
954.060967265
[[0.0, -356214.3943757172, 0.0]]
946.75375456
[[0.0, -243785.6056242822, 0.0]]
939.283539129
[[0.0, -139251.96150630055, 0.0]]
931.704832793
[[0.0, -57294.90168751533, 0.0]]
924.099724048
[[0.0, -9425.051661410507, 0.0]]
916.501371709
[[0.0, -2365.5896056567476, 0.0]]
908.91719647
[[0.0, -37107.99598684137, 0.0]]

[quentin]

Hi Hugo,

I just tried to implement the code you proposed and it’s working. I made a loop to find the point at the end of my shape (the point with the biggest x coordinate) before the beginning of the scene :

def bwdInitGraph(self,node):
        # find the position at the end of the shape (which has the biggest x coordinate)
        Positions = self.MechaNode.findData('position').value
        max = 0
        for i in range(len(Positions)):
            if Positions[i][0] > max:
                self.pos = i
                max = Positions[i][0]
        print(self.pos)
        print(Positions[self.pos][0])
        return 0

After that, I just displayed the value at each time step like that :

   # called on each animation step (end)
    def onEndAnimationStep(self, dt):
        # access the 'position' state vector
        Positions = self.MechaNode.findData('position').value
        # print the value of the DOF self.pos (Vec3 : x,y,z) x for 0, y for 1, z for 2
        print str(Positions[self.pos][0])
        return 0

Thank’s for your help !

[quentin]

Hi Hugo,

It’s perfect thank you ! I just have a last question about the point you can access. How can you find the label of the point ? I mean that I want to choose a specific point of the mesh, so how to proceed ? Do I have to look inside the mesh file and find the good line for the point and that’s the label I have to use in x here myMOpositions[x][0] ?

Thank’s for you help !

[quentin]

Thanks for the answer, I just added accordion.createObject('MechanicalObject', name='tetras', template='Vec3d', showObject="1") and it changed nothing

I think I have a problem with the loader and there is no object so the box isn’t defined.

[quentin]

It works, thank’s ! The error was the GUI which is QGL by default.

Quentin

[quentin]

-> subject moved to the SoftRobots Github page

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