test.cc

class MyUserFunction : public apf::Function
{
public:
	MyUserFunction(apf::Field* f, apf::Mesh* m) : node_field(f), mesh(m) {}

	void eval(apf::MeshEntity* e, double *result) {
		if(NULL != node_field) {
			apf::MeshElement* me = apf::createMeshElement(this->mesh, e);
			apf::Element* f_elm = apf::createElement(this->node_field, me);
			/*find the location of the single node on entity*/
			apf::Vector3 tmp_vec;
			apf::getVector(this->node_field, e, 0, tmp_vec);

			apf::Vector3 x_vec;
			apf::mapLocalToGlobal(me, tmp_vec, x_vec);
			*result = (2*x_vec[0] + 5*x_vec[1]);
		} else {
			std::cout << "failed to set field" << std::endl;
			*result = -1.0;
		}

	}

protected:
	apf::Field* node_field;
	apf::Mesh* mesh;

};
void test(){
	apf::Mesh2* m = NULL;
	this->mesh_builder->buildBatmanElementMesh(m);

	apf::MeshIterator* it;
	apf::MeshEntity* e;
	it = m->begin(2);
	e = m->iterate(it);
	m->end(it);

	apf::Field* node_f = apf::createField(m, "nodeField", apf::SCALAR, m->getShape());
	// apf::zeroField(node_f);
	MyUserFunction test_fnc(node_f, m);
	apf::Field* test_f = apf::createUserField(m, "testingField", apf::SCALAR, m->getShape(), &test_fnc);

	apf::MeshElement* me = apf::createMeshElement(m, e);
	apf::Element* f_elm = apf::createElement(test_f, me);

	/*pick a random spot inside the element coordinates*/
	apf::Vector3 sample_points[8] =
	{apf::Vector3(-0.1241,    0.4889, 0.0),
	 apf::Vector3( 0.4897,    0.0347, 0.0),
	 apf::Vector3( 0.4090,    0.7269, 0.0),
	 apf::Vector3( 0.4172,   -0.3034, 0.0),
	 apf::Vector3( 0.6715,    0.2939, 0.0),
	 apf::Vector3(-0.2075,   -0.7873, 0.0),
	 apf::Vector3( 0.7172,    0.8884, 0.0),
	 apf::Vector3( 0.6302,   -0.1471, 0.0)};
	for(uint32_t ii = 0; ii < 8; ++ii) {
		apf::Vector3 tmp_grad(0.0, 0.0, 0.0);
		apf::getGrad(f_elm, sample_points[ii], tmp_grad);
		EXPECT_FLOAT_EQ(2.0, tmp_grad[0]);
		EXPECT_FLOAT_EQ(5.0, tmp_grad[1]);
	} 
	apf::writeVtkFiles("batman_elm", m);
}