How to combine a set of shapes into one shape

TopoDS_Compound

Thanks for your answer, I've tried to Add all shapes to a TopoDS_Compund, then exported the Compound to STEP file. When openning the STEP file in Solidworks, there is still many parts. Moving any part, it will separate from the model.

I have exactly the same question.

If you want to export into Step as one single compaund you need to update parameter

STEPCAFControl_Controller::Init();
Interface_Static::SetCVal("write.step.assembly","Off"); 

Best regards, Commenter-3.

Hi Dmitrii. Thanks for your answer. However, it doesn't solve the problem in my case. Setting this parameter flattens the objects hierarchy tree - the resulting step file has one root compound and all solids/shells as its children, i.e. the tree depth is 1. I need the step file to have just one shape, i.e. a tree depth of 0. Do you any ideas how to achieve that?

In that case you need to perform Boolean operation - fuse. Your goal is not related with step format.

Best regards, Commenter-3.

I did try the fuse operation via BOPAlgo_Builder, but it completely preserves the hierarchy of objects. I didn't find an option to disable that.

Here's my code:

TDF_Label top_label;
char* path;
//...
BOPAlgo_Builder builder;
std::queue<TDF_Label> queue;
queue.push(top_label);

while (!queue.empty())
{
    TDF_Label label = queue.front();
    queue.pop();

    if (TDF_LabelSequence children_labels; XCAFDoc_ShapeTool::GetComponents(label, children_labels))
    {
        for (const TDF_Label &child_label : children_labels)
        {
            queue.push(child_label);
        }
    }
    else if (TopoDS_Shape shape; XCAFDoc_ShapeTool::GetShape(label, shape))
    {
        builder.AddArgument(shape);
    }
}

builder.Perform();

STEPControl_Writer writer;
writer.Transfer(builder.Shape(), STEPControl_StepModelType::STEPControl_AsIs);
writer.Write(path);

Here's the result: