OCC网格模型导入unity

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1.使用OpenCasCade创建好brep后,对边界表达的模型进行网格化处理.

2.occ 网格化处理参照了 OSG plugin下 occ的

osg::Node* BuildShapeMesh(const TopoDS_Shape&amp; aShape)
{
	osg::ref_ptr&lt;osg::Vec3Array> vertexList = new osg::Vec3Array();
	osg::ref_ptr&lt;osg::Group> root = new osg::Group();

	osg::ref_ptr&lt;osg::Geode> geode = new osg::Geode();

	//osg::Array::Binding colorBinding = osg::Array::BIND_OVERALL;

	// vector to save _colorTool
	//osg::ref_ptr&lt;osg::Vec3Array> colorList = new osg::Vec3Array();

	// create one osg primitive set
	osg::ref_ptr&lt;osg::DrawElementsUInt> triangleStrip = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);
	unsigned int noOfTriangles = 0;

	osg::ref_ptr&lt;osg::Geometry> geom = new osg::Geometry;

	gim::EntityPoints1 ep;

	// large vertex datasets work best with VBO.
	geom->setUseVertexBufferObjects(true);

	if (!aShape.IsNull())
	{
		// clean any previous triangulation
		BRepTools::Clean(aShape);

		//_healShape(shape);

		/// call to incremental mesh on this shape
		/// \todo not sure why this 1 is passed. Its called deflection BTW
		///       need to find a way to calculate it
		double linearDeflection = 1.0;
		BRepMesh_IncrementalMesh(aShape, linearDeflection);

		///iterate faces
		// this variable will help in keeping track of face indices
		unsigned int index = 0;
		
		
		for (TopExp_Explorer ex(aShape, TopAbs_FACE); ex.More(); ex.Next())
		{
			
			TopoDS_Face face = TopoDS::Face(ex.Current());
			TopLoc_Location location;

			/// triangulate current face
			Handle(Poly_Triangulation) triangulation = BRep_Tool::Triangulation(face, location);
			if (!triangulation.IsNull())
			{
				int noOfNodes = triangulation->NbNodes();

				// Store vertices. Build vertex array here
				for (int j = 1; j &lt;= triangulation->NbNodes(); j++)
				{
					// populate vertex list
					// Ref: http://www.opencascade.org/org/forum/thread_16694/?forum=3
					gp_Pnt pt = (triangulation->Nodes())(j).Transformed(location.Transformation());
					vertexList->push_back(osg::Vec3(pt.X(), pt.Y(), pt.Z()));

				}
				/// now we need to get face indices for triangles
				// get list of triangle first
				const Poly_Array1OfTriangle&amp; triangles = triangulation->Triangles();

				//No of triangles in this triangulation
				noOfTriangles = triangulation->NbTriangles();

				Standard_Integer v1, v2, v3;
				for (unsigned int j = 1; j &lt;= noOfTriangles; j++)
				{
					/// If face direction is reversed then we add verticews in reverse order
					/// order of vertices is important for normal calculation later
					if (face.Orientation() == TopAbs_REVERSED)
					{
						triangles(j).Get(v1, v3, v2);
					}
					else
					{
						triangles(j).Get(v1, v2, v3);
					}
					triangleStrip->push_back(index + v1 - 1);
					triangleStrip->push_back(index + v2 - 1);
					triangleStrip->push_back(index + v3 - 1);
				}
				index = index + noOfNodes;
			}
		}

		geom->setVertexArray(vertexList.get());

		geom->addPrimitiveSet(triangleStrip.get());
	}
	osg::Vec3Array* vs = dynamic_cast&lt;osg::Vec3Array*>(vertexList->asArray());

	vertex = new float&#91;vs->size() * 3];
	indices = new  int&#91;triangleStrip->size()];

	vertexcount = vs->size();

	for (int i = 0; i &lt; vs->size(); i++)
	{
		vertex&#91;i * 3] = vs->at(i).x();
		vertex&#91;i * 3 + 1] = vs->at(i).y();
		vertex&#91;i * 3 + 2] = vs->at(i).z();
	}
	for (int i = 0; i &lt; triangleStrip->size(); i++)
	{
		indices&#91;i] = triangleStrip->getElement(i);

	}

	geode->addDrawable(geom);

	root->addChild(geode);
	//osgDB::writeNodeFile(*root, "saved.osg");
	return root.release();
}

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osg::Node* BuildShapeMesh(const TopoDS_Shape& aShape)

{

osg::ref_ptr<osg::Vec3Array> vertexList = new osg::Vec3Array();

osg::ref_ptr<osg::Group> root = new osg::Group();

osg::ref_ptr<osg::Geode> geode = new osg::Geode();

//osg::Array::Binding colorBinding = osg::Array::BIND_OVERALL;

// vector to save _colorTool

//osg::ref_ptr<osg::Vec3Array> colorList = new osg::Vec3Array();

// create one osg primitive set

osg::ref_ptr<osg::DrawElementsUInt> triangleStrip = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);

unsigned int noOfTriangles = 0;

osg::ref_ptr<osg::Geometry> geom = new osg::Geometry;

gim::EntityPoints1 ep;

// large vertex datasets work best with VBO.

geom->setUseVertexBufferObjects(true);

if (!aShape.IsNull())

{

// clean any previous triangulation

BRepTools::Clean(aShape);

//_healShape(shape);

/// call to incremental mesh on this shape

/// \todo not sure why this 1 is passed. Its called deflection BTW

/// need to find a way to calculate it

double linearDeflection = 1.0;

BRepMesh_IncrementalMesh(aShape, linearDeflection);

///iterate faces

// this variable will help in keeping track of face indices

unsigned int index = 0;

for (TopExp_Explorer ex(aShape, TopAbs_FACE); ex.More(); ex.Next())

{

TopoDS_Face face = TopoDS::Face(ex.Current());

TopLoc_Location location;

/// triangulate current face

Handle(Poly_Triangulation) triangulation = BRep_Tool::Triangulation(face, location);

if (!triangulation.IsNull())

{

int noOfNodes = triangulation->NbNodes();

// Store vertices. Build vertex array here

for (int j = 1; j <= triangulation->NbNodes(); j++)

{

// populate vertex list

// Ref: http://www.opencascade.org/org/forum/thread_16694/?forum=3

gp_Pnt pt = (triangulation->Nodes())(j).Transformed(location.Transformation());

vertexList->push_back(osg::Vec3(pt.X(), pt.Y(), pt.Z()));

}

/// now we need to get face indices for triangles

// get list of triangle first

const Poly_Array1OfTriangle& triangles = triangulation->Triangles();

//No of triangles in this triangulation

noOfTriangles = triangulation->NbTriangles();

Standard_Integer v1, v2, v3;

for (unsigned int j = 1; j <= noOfTriangles; j++)

{

/// If face direction is reversed then we add verticews in reverse order

/// order of vertices is important for normal calculation later

if (face.Orientation() == TopAbs_REVERSED)

{

triangles(j).Get(v1, v3, v2);

}

else

{

triangles(j).Get(v1, v2, v3);

}

triangleStrip->push_back(index + v1 - 1);

triangleStrip->push_back(index + v2 - 1);

triangleStrip->push_back(index + v3 - 1);

}

index = index + noOfNodes;

}

geom->setVertexArray(vertexList.get());

geom->addPrimitiveSet(triangleStrip.get());

}

osg::Vec3Array* vs = dynamic_cast<osg::Vec3Array*>(vertexList->asArray());

vertex = new float[vs->size() * 3];

indices = new int[triangleStrip->size()];

vertexcount = vs->size();

for (int i = 0; i < vs->size(); i++)

{

vertex[i * 3] = vs->at(i).x();

vertex[i * 3 + 1] = vs->at(i).y();

vertex[i * 3 + 2] = vs->at(i).z();

}

for (int i = 0; i < triangleStrip->size(); i++)

{

indices[i] = triangleStrip->getElement(i);

}

geode->addDrawable(geom);

root->addChild(geode);

//osgDB::writeNodeFile(*root, "saved.osg");

return root.release();

}

3. 最后将网格化后的数据进行到Unity

C++端

&#91;DllImport("brep")]

public static extern void GetVertex(out IntPtr vertex_data,out IntPtr indices_data, out int size);

[DllImport("brep")]

public static extern void GetVertex(out IntPtr vertex_data,out IntPtr indices_data, out int size);

Unity端

UnityExport void GetVertex(float** vertex_data, int** indices_data, int* size)
{
	BuildShapeMesh(test());
	*vertex_data = vertex;
	*indices_data = indices;
	*size = vertexcount;
}

UnityExport void GetVertex(float** vertex_data, int** indices_data, int* size)

{

BuildShapeMesh(test());

*vertex_data = vertex;

*indices_data = indices;

*size = vertexcount;

}

4. 注意在OSG中查看 occ 模型要注意开启

state->setMode(GL_CULL_FACE, osg::StateAttribute::ON);

1	state->setMode(GL_CULL_FACE, osg::StateAttribute::ON);

如果不开启,将进行双面材质的渲染, 不容易区分索引到底对不对.

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