Introduce a set of Cpp examples for the new volumetric extension

[vijaiaeroastro]

This PR introduces the following Cpp volumetric examples to the develop branch

Creating implicit shapes

• Sphere
• Torus
• Gyroid
• Cylinder

Then two additional examples

• Combine functions
• Volume from Image stack

These have been build using the unit tests created by @3dJan. I can add more examples based on your suggestions.

• FillMeshWithGyroid

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.09%. Comparing base (932f2d6) to head (3824e5f).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #400   +/-   ##
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  Coverage    66.09%   66.09%           
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  Files          395      395           
  Lines        44642    44642           
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  Hits         29506    29506           
  Misses       15136    15136           

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[3dJan]

The examples do not run on my machine due to the use of r-values in the AddLink method. Or maybe it is a lifetime issue of the shared ptr loosing references to early.

[3dJan]

This version crashes at least on windows with msvc. AddLink(...) only works with l-values, an act issue I could not resolve.

cosNode is missing an input.

[3dJan]

This might work:

int main() {
    Lib3MF::PWrapper wrapper = Lib3MF::CWrapper::loadLibrary();
    auto model = wrapper->CreateModel();

    auto gyroidFunction = model->AddImplicitFunction();
    gyroidFunction->SetDisplayName("Gyroid");

    auto input = gyroidFunction->AddInput("pos", "position", Lib3MF::eImplicitPortType::Vector);
    auto sinNode = gyroidFunction->AddSinNode("sin", Lib3MF::eImplicitNodeConfiguration::VectorToVector, "Sine of Position", "group");
    auto cosNode = gyroidFunction->AddCosNode("cos", Lib3MF::eImplicitNodeConfiguration::VectorToVector, "Cosine of Transformed Position", "group");

    auto dotNode = gyroidFunction->AddDotNode("dot", "Dot Product", "group");
    auto sinInputA = sinNode->GetInputA();
    gyroidFunction->AddLink(input, sinInputA);

    auto cosInputA = cosNode->GetInputA();
    gyroidFunction->AddLink(input, cosInputA);
    auto dotInputA = dotNode->GetInputA();
    auto dotInputB = dotNode->GetInputB();

    auto cosResult = cosNode->GetOutputResult();
    auto sinResult = sinNode->GetOutputResult();
    gyroidFunction->AddLink(cosResult, dotInputB);
    gyroidFunction->AddLink(sinResult, dotInputA);

    auto output = gyroidFunction->AddOutput("shape", "Signed Distance Field", Lib3MF::eImplicitPortType::Scalar);
    auto dotResult = dotNode->GetOutputResult();
    gyroidFunction->AddLink(dotResult, output);

    auto writer = model->QueryWriter("3mf");
    writer->WriteToFile("Gyroid.3mf");

    std::cout << "Saved Gyroid.3mf" << std::endl;
    return 0;
}

[3dJan]

Just created a PR to ACT for the fix: PR in ACT

[vijaiaeroastro]

@3dJan How come the unit tests run then ? They also link to the same library right ?

[3dJan]

@vijaiaeroastro The unit tests don't use the return value directly, but store the return value, a shared_ptr, in a variable. That keeps the shared_ptr alive, otherwise it would currently go out of scope without the suggested fix. The API tries to access the already stored raw pointer and fails. See also my comment in PR in ACT.

[vijaiaeroastro]

@3dJan @gangatp I have removed all the other examples and kept only one from @3dJan. We can introduce more later.