[vtkusers] pipeline setup question

[Geoff Woodcock]

Hi,

I've created a pipeline to try and do "collision detection" for use with copy/paste using vtkIntersectionPolyDataFilter. Basically, I get a set of bounding boxes for objects already in the scene and then another set for the objects being pasted. Then I move the position of the pasted objects around, recalculate the bounding boxes, and test for intersection until it fails.

The pipeline is like this:

CubeSource(1..n) -> appendfilter -> geometry filter -> trianglefilter -intersectfilter

2 pipelines, one for objects already in scene, one for objects being pasted.

I have several problems:


  *   vtkIntersectionPolyDataFilter crashes sometimes when there are multiple objects in the scene or being pasted. It might be a known bug related to https://gitlab.kitware.com/vtk/vtk/commit/eb975a3742de5aa5592fbb7ba2dd4726c9a51313
  *   vtkIntersectionPolyDataFilter does not handle the case where one object is inside of the other (no intersection occurs)
  *   I tried to work around this bug by testing each bounding box separately. So I assign the cubesources one at a time to the appendfilter. When I do this, I get a message, "Can't build OBB tree, no data available", followed by a crash in vtkOBBTree::DisjointOBBNodes. ("nodeA was nullPtr")

Other than an any general advice anyone can give me, can anyone explain the third  item? If I assign the cubesources as I build the pipeline, it works correctly. But if I assign them after the pipeline is built, it crashes...why? There is something fundamental I am not understanding about the pipeline.

Here is my messy test code... commenting and uncommenting the two indicated lines makes the crash come and go...

    vtkSmartPointer<vtkIntersectionPolyDataFilter> intersectFilter = vtkSmartPointer<vtkIntersectionPolyDataFilter>::New();
    vtkSmartPointer<vtkAppendFilter> appendFilter = vtkSmartPointer<vtkAppendFilter>::New();

    // get bounding box of all existing actors
    std::vector<std::vector<double>> bboxes;
    std::vector<vtkSmartPointer<vtkCubeSource>> cubes;
    double bounds[6];
    double maxBounds[3] = {0};
    for (const auto& object : doc->getChildren()) {
        auto actor = vtkProp3D::SafeDownCast(Core::Application::get()->getContext().getActorForPart(object));
        if (actor->GetPickable()) {
            double origin[3];
            actor->GetOrigin(origin);
            actor->GetBounds(bounds);
            if (bounds[1] > maxBounds[0]) {
                maxBounds[0] = bounds[1];
            }
            if (bounds[3] > maxBounds[1]) {
                maxBounds[1] = bounds[3];
            }
            if (bounds[5] > maxBounds[2]) {
                maxBounds[2] = bounds[5];
            }
        }
        std::vector<double> values = {bounds[0], bounds[1], bounds[2], bounds[3], bounds[4], bounds[5], bounds[6]};
        bboxes.push_back(values);
        vtkSmartPointer<vtkCubeSource> cube = vtkSmartPointer<vtkCubeSource>::New();
        cube->SetBounds(bounds);
        cube->Update();
        cubes.push_back(cube);
        appendFilter->AddInputConnection(cube->GetOutputPort()); // <---- works if I add connections here.
    }
    vtkSmartPointer<vtkGeometryFilter> geometryFilter = vtkSmartPointer<vtkGeometryFilter>::New();
    geometryFilter->SetInputConnection(appendFilter->GetOutputPort());
    vtkSmartPointer<vtkTriangleFilter> triFilter = vtkSmartPointer<vtkTriangleFilter>::New();
    triFilter->SetInputConnection(geometryFilter->GetOutputPort(0));
    intersectFilter->SetInputConnection(0, triFilter->GetOutputPort());

    // get bounding box of all objects
    std::vector<vtkSmartPointer<vtkCubeSource>> pasteObjectBounds;
    vtkSmartPointer<vtkAppendFilter> pastedObjAppendFilter = vtkSmartPointer<vtkAppendFilter>::New();

    for (const auto& object : _copyPasteBuffer) {
        vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
        polyData->ShallowCopy(object->data());
        polyData->ComputeBounds();
        polyData->GetBounds(bounds);
        vtkSmartPointer<vtkCubeSource> cube = vtkSmartPointer<vtkCubeSource>::New();
        auto layout = object->layout();
        auto x = layout._matrix->GetElement(0, 3);
        auto y = layout._matrix->GetElement(1, 3);
        cube->SetBounds(bounds);
        cube->SetCenter(x, y, 0);
        cube->Update();
        pastedObjAppendFilter->AddInputConnection(cube->GetOutputPort());

        pasteObjectBounds.push_back(cube);
    }

    pastedObjAppendFilter->Update();
    vtkSmartPointer<vtkGeometryFilter> pastedObjGeometryFilter = vtkSmartPointer<vtkGeometryFilter>::New();
    pastedObjGeometryFilter->SetInputConnection(pastedObjAppendFilter->GetOutputPort());
    pastedObjGeometryFilter->Update();
    vtkSmartPointer<vtkTriangleFilter> pasteTriFilter = vtkSmartPointer<vtkTriangleFilter>::New();
    pasteTriFilter->SetInputConnection(pastedObjGeometryFilter->GetOutputPort(0));
    pasteTriFilter->Update();
    vtkSmartPointer<vtkCleanPolyData> pasteCleanData = vtkSmartPointer<vtkCleanPolyData>::New();
    pasteCleanData->SetInputConnection(pasteTriFilter->GetOutputPort());
    pasteCleanData->Update();

    intersectFilter->SetInputConnection(1, pasteCleanData->GetOutputPort());

    bool foundASpot = false;
    auto polyData = vtkPolyData::SafeDownCast(pastedObjGeometryFilter->GetOutputDataObject(0));
    polyData->ComputeBounds();
    polyData->GetBounds(bounds);
    double p1[3] = {bounds[0], bounds[2], 0};
    double p2[3] = {bounds[1], bounds[3], 0};

    double length = sqrt(vtkMath::Distance2BetweenPoints(p1, p2));
    double step = length / 4.0;
    double radius = 0;
    while (!foundASpot) {
        for (int ii = 0; ii < 6 && !foundASpot; ii++) {
            double angle = 45 * ii;
            double x = radius * sin(angle);
            double y = radius * cos(angle);

            for (auto cube : pasteObjectBounds) {
                double center[3];
                cube->GetCenter(center);
                center[0] += x;
                center[1] += y;
                cube->SetCenter(center);
                cube->Update();
                cube->Modified();
            }

            // check for intersection.
            foundASpot = true;
            for (auto cube : cubes) {
                //appendFilter->SetInputConnection(cube->GetOutputPort());// <----fails if I set input connection here.
                appendFilter->Update();
                appendFilter->Modified();
                geometryFilter->Update();
                geometryFilter->Modified();
                triFilter->Update();
                triFilter->Modified();
                intersectFilter->Update();
                if (intersectFilter->GetNumberOfIntersectionPoints()) {
                    foundASpot = false;
                }
            }
            if (!foundASpot) {
                for (auto pasteCubes : pasteObjectBounds) {
                    double center[3];
                    pasteCubes->GetCenter(center);
                    center[0] -= x;
                    center[1] -= y;
                    pasteCubes->SetCenter(center);
                    pasteCubes->Update();
                    pasteCubes->Modified();
                }
            } else {
                // found a spot!
                foundASpot = true;
                maxBounds[0] = x;
                maxBounds[1] = y;
            }
        }

        radius += step;
    }



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