[Wong]

@hugo, could you give me a reply?

[Wong]

Thank you @hugo,

After a lot of testing, the performance can be indeed improved if I simplify the mesh of the model. I will try my utmost to make my scene simple afterwards.

Thank you for your theoretical and detailed reply again.

[Wong]

Hello, I have solved the problem. Thank you.

[Wong]

Hello @hugo,

I think my solution is not the best one because it is fairly complex and use many components. In fact, my mesh object is in fact not a cylinder as the picture you can see. It is a more complex mesh which does not have a smooth flat cut. So I use the SubsetTopologicalMapping component.

But I do not think it is an elegant method. Because it would be troublesome if it is used in real time cutting. One cut has resulted in so much code, let alone the situation when many cuts occur, although I am not sure if the smooth flat one would have the similar problem.

So I still want a more elegant method.

By the way, can you answer my new question at this link?

[Wong]

Hello @hugo

Thank you. I have solved the problem

[Wong]

Hello @hugo,

It is indeed a deformable object with an initial cut/crevice, but not an auto-collision model.
I mean the problem is not the collision. You can even use the visual model instead.

The problem is the BarycentricMapping. The mapping would be not correct if such mesh is used to map to the tetrahedral mesh. The vertices of the crevice would map to the same tetrahedron.

Now can you understand it?

Wong

[Wong]

Hello @hugo,

I think it should be a solution because I have tried it as well before. But now I do not use the beams in my scene any more.

By the way, can you answer my another question at this link?

How to model a deformable object with a deep crevice?

[Wong]

Hi @hkomninos,

FreeMotionAnimationLoop::SPtr loop = sofa::core::objectmodel::New<FreeMotionAnimationLoop>(groot.get());
	loop->setName("Loop");
	groot->addObject(loop);

[Wong]

Hello @meldiwiny,

Thank you.

This topic can be ignored. I have solved the problem.

[Wong]

Hello everyone,

This topic can be ignored. I have solved the problem.

[Wong]

Hello @meldiwiny,
Have you found the local frames?
I am eager to use them and waiting for your good news daily.

[Wong]

Hello @meldiwiny,

Yes. It is just the kind of scene I am looking for, as the figures shown above. I want to map the beams to the local frames. How can I implement it?

The visualization of the local frames is not necessary, but it would be fine if they do.

[Wong]

Hello @hugo,
I think this is the feature of the component in Sofa. It is no reason that you have no impression about this. The paper(figure 2) mentions about these local frames and you can know about it by reading this paper.

[Wong]

Hello @hugo,
Increasing both the alarmDistance and contactDistance is sure to be fine, but the animation would become slow. How to address this issue?

[Wong]

Hello @hugo,

Just V17.12, can you help me?

[Wong]

Hello @hugo,
Thank you, I have solved the problem.

[Wong]

Hi @hugo,
Where is the topic info?

[Wong]

Hello @hugo,
1)I have read the paper and the paper mentions a mapping between a tetrahedron and a 6DoF-beam node. Does such a mapping exist in current Sofa version?

2)I have read the BeamFEMForceField.scn and it runs fine. But when I add the FreeMotionAnimationLoop component into this scene, as shown below, the collision model behaves unnormally.

<Node name="root" dt="0.005">
    <RequiredPlugin pluginName="SofaMiscCollision" />
    <VisualStyle displayFlags="showBehaviorModels showForceFields showCollisionModels" />
    <CollisionPipeline depth="6" verbose="0" draw="0" />
    <BruteForceDetection name="N2" />
    <CollisionResponse name="response" response="FrictionContact" />
    <LocalMinDistance name="proximity" alarmDistance="0.15" contactDistance="0.05" angleCone="0.0" />
    <FreeMotionAnimationLoop/>
    <LCPConstraintSolver tolerance="0.001" maxIt="1000"/>
    <!--<CollisionGroup name="Group" />-->
    <Node name="beam">
        <EulerImplicit rayleighStiffness="0" printLog="false"  rayleighMass="0.1" />
        <BTDLinearSolver template="BTDMatrix6d" printLog="false" verbose="false" />
        <MechanicalObject template="Rigid" name="DOFs" size="8" position="0 0 0 0 0 0 1  1 0 0 0 0 0 1  2 0 0 0 0 0 1  3 0 0 0 0 0 1  4 0 0 0 0 0 1  5 0 0 0 0 0 1  6 0 0 0 0 0 1  7 0 0 0 0 0 1" />
        <Mesh name="lines" lines="0 1 1 2 2 3 3 4 4 5 5 6 6 7" />
        <FixedConstraint name="FixedConstraint" indices="0" />
        <UniformMass mass="1 1 0.01 0 0 0 0.1 0 0 0 0.1" printLog="false" />
        <BeamFEMForceField name="FEM" radius="0.1" youngModulus="20000000" poissonRatio="0.49"/>
        <PrecomputedConstraintCorrection recompute="1"/>
        <Node name="Collision">
            <!--        <CubeTopology nx="115" ny="4" nz="4" xmin="0" xmax="7" ymin="-0.1" ymax="0.1" zmin="-0.1" zmax="0.1" /> -->
            <CubeTopology nx="15" ny="2" nz="2" min="0 -0.1 -0.1" max="7 0.1 0.1" />
            <MechanicalObject />
            <BeamLinearMapping isMechanical="true" />
            <Triangle />
        </Node>
    </Node>
</Node>

3) The blood vessel I want to represent is not an ordinary one. It is an artery with an aneurysm. So what is the best way to simulate such a blood vessel?

[Wong]

Hello @epernod,

I have searched some information. To be used in C#, a C function (if it returns a C++ class object) is usually wrapped into a particular form to return the C++ class pointer of the object and exported in a .dll file. Then the P/Invoke Interop is used to import the C function in C# and the corresponding object of the returned value is a IntPtr type object.

Do you do like that? Thanks.

[Wong]

Hello @epernod,

If the C bindings are used, the C++ class object must be returned when the C function ends, or it will be destroyed. But the corresponding type cannot be found in C#. So how to address this issue?

Thanks.

[Wong]

Hello @epernod,

Can you tell me where I can learn about C bindings? Thanks.

[Wong]

Hello @epernod,

As far as I know, Native Plugin seemingly cannot export C++ classes in C#. So how to use Sofa C++ classes in C#?

The data structure type in C++ is different from that in C#.So how to pass the data from C++ to C# ?

[Wong]

Hello @epernod ,

Which way do you use to combine Sofa with Unity? Managed Plugins or Native Plugins? How to use the C++ classes in C#?

The data structure type in C++ is different from that in C#.So how to pass the data from C++ to C# ?

[Wong]

Hello @alexbilger ,

Which way do you use to combine Sofa with Unity? Managed Plugins or Native Plugins? How to use the C++ classes in C#?

The data structure type in C++ is different from that in C#.So how to pass the data from C++ to C# ?

[Wong]

Hi @mtournie

Max,could you give me a reply?

[Author]

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