# vtkRenderWindow memory leak

**URL:** <https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612>\
**Category:** Support\
**Tags:** python\
**Created:** [February 3, 2023, 8:44pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612 "2023-02-03T20:44:51Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![skoudoro](https://discourse.vtk.org/user_avatar/discourse.vtk.org/skoudoro/32/4568_2.png) [@skoudoro](https://discourse.vtk.org/u/skoudoro)\
**Post date:** [February 3, 2023, 8:44pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/1 "2023-02-03T20:44:51Z")

</div>

Hi VTK Team

I encounter a memory leak when use the code below, RAM utilization is going up.

It seems that vtkRenderWindow is not freed correctly. If I put out of the loop vtkRenderwindow, everything is ok.

Also, It seems to be an old problem as you can see here ([RAM blow out when looping vtkRenderWindow render](https://discourse.vtk.org/t/ram-blow-out-when-looping-vtkrenderwindow-render/3034)). This problem is still present on the last release.

```python
def test_memory_leak():
    colors = vtkNamedColors()

    # create source
    source = vtkSphereSource()
    source.SetCenter(0, 0, 0)
    source.SetRadius(5.0)
    source.SetPhiResolution(30)
    source.SetThetaResolution(30)

    # mapper
    mapper = vtkPolyDataMapper()
    mapper.SetInputConnection(source.GetOutputPort())

    # actor
    actor = vtkActor()
    actor.GetProperty().SetColor(colors.GetColor3d('IndianRed'))
    actor.GetProperty().SetSpecular(0.6)
    actor.GetProperty().SetSpecularPower(30)
    actor.SetMapper(mapper)

    for time in range(200):
        # create a rendering window and renderer
        ren = vtkRenderer()
        renWin = vtkRenderWindow()
        renWin.AddRenderer(ren)
        renWin.SetWindowName('Screenshot')

        # create a renderwindowinteractor
        iren = vtkRenderWindowInteractor()
        iren.SetRenderWindow(renWin)

        #renwin offscreen
        renWin.SetOffScreenRendering(1)

        # assign actor to the renderer
        ren.AddActor(actor)
        ren.SetBackground(colors.GetColor3d('MistyRose'))

        renWin.Render()

        # screenshot code:
        w2if = vtkWindowToImageFilter()
        w2if.SetInput(renWin)
        w2if.SetInputBufferTypeToRGB()
        w2if.ReadFrontBufferOff()
        w2if.Update()

        writer = vtkPNGWriter()
        writer.SetFileName('file%02d.png' % time)
        writer.SetInputConnection(w2if.GetOutputPort())
        writer.Write()

test_memory_leak()

```

I am on macOsX M1, using rosetta system (x86\_64), python 3.9.13, vtk 9.2.5

---

<div class="post-metadata">

**Author:** ![skoudoro](https://discourse.vtk.org/user_avatar/discourse.vtk.org/skoudoro/32/4568_2.png) [@skoudoro](https://discourse.vtk.org/u/skoudoro)\
**Post date:** [February 3, 2023, 9:06pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/2 "2023-02-03T21:06:09Z")

</div>

Not sure, but it seems related and they are working on it : [https://gitlab.kitware.com/vtk/vtk/-/issues/18573](https://gitlab.kitware.com/vtk/vtk/-/issues/18573)

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [February 4, 2023, 10:28pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/3 "2023-02-04T22:28:04Z")

</div>

Hello,

I’m not sure whether that such test can realiably diagnose a leak. I see a loop that creates 400 objects and Python’s garbage colletion and memory management are a black box. I believe you can try forcing a GC after running the loop and then measure memory consumption.

best,

Paulo

---

<div class="post-metadata">

**Author:** ![skoudoro](https://discourse.vtk.org/user_avatar/discourse.vtk.org/skoudoro/32/4568_2.png) [@skoudoro](https://discourse.vtk.org/u/skoudoro)\
**Post date:** [February 8, 2023, 10:11pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/4 "2023-02-08T22:11:12Z")

</div>

Thank you for your feedback @Paulo_Carvalho

I followed your advice, and simplify the loop. I still observe a leak. The RAM is slowly increasing. See below the code:

```python
def test_memory_leak():
      for time in range(200):
              gc.collect()
              ren = vtkRenderer()
              renWin = vtkRenderWindow()
              renWin.AddRenderer(ren)
              renWin.SetWindowName('Screenshot')
              gc.collect() 

test_memory_leak()

```

It’s been a very long time, I did not need to touch C++. I will try to find the time to reproduce this example and see if I observe this leak in C++ also.

---

<div class="post-metadata">

**Author:** ![afa](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/a/e9bcb4/32.png) [@afa](https://discourse.vtk.org/u/afa)\
**Post date:** [February 15, 2023, 2:21pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/5 "2023-02-15T14:21:10Z")

</div>

This user is also testing memory leaks, in C++ code: [Memory leak occurs if I use vtkSmartPointer in sub-thread. - #2 by sohnishi](https://discourse.vtk.org/t/memory-leak-occurs-if-i-use-vtksmartpointer-in-sub-thread/10631/2)  
You could take inspiration from his code + VTK examples + VTK\_DEBUG\_LEAKS

---

<div class="post-metadata">

**Author:** ![gpu](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/g/e47c2d/32.png) [@gpu](https://discourse.vtk.org/u/gpu)\
**Post date:** [December 15, 2023, 2:52am UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/6 "2023-12-15T02:52:31Z")

</div>

how about it in C++?

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 8:11am UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/7 "2024-03-07T08:11:36Z")

</div>

I have just encountered this same issue in c++. Version 9.2.x, MacOS, Intel silicon. The render window is not closing, possibly having to do with using vtkPNGWriter and no window interactor. When run in lldb, after 100 iterations a warning pops up saying “[Window] WARNING: NSWindow has detected an excessive live window count of 101. Window 0x1e69 of class ‘NSWindow’ created after passing the threshold of 100.” I’ll post the backtrace at the bottom here.

I encountered this at first creating the renderWindow inside a function that is looped, then tried a workaround where a single renderWindow is passed into the function inside the loop. In every case, Finalize() is supposed to free the resources, but does not. More troubling is the fact that even the object going out of scope (when inside the function it was wrapped in a vtkNew) does not free the resources.

As a side note, I tried to run VTK\_DEBUG\_LEAKS but couldn’t get it to report anything. If anyone knows a good tutorial that would be really helpful.

```auto
[Window] WARNING: NSWindow has detected an excessive live window count of 101. Window 0x1e69 of class 'NSWindow' created after passing the threshold of 100. This window is not necessarily the cause, and this warning will only be shown once per window class. (
        0 AppKit 0x00007ff811a41b35 -[NSWindow _setWindowNumber:] + 837
        1 AppKit 0x00007ff8123cc4ef _NXCreateWindow + 278
        2 AppKit 0x00007ff811b4d71e -[NSWindow _commonAwake] + 871
        3 AppKit 0x00007ff811a40b5f -[NSWindow _commonInitFrame:styleMask:backing:defer:] + 1209
        4 AppKit 0x00007ff811a40290 -[NSWindow _initContent:styleMask:backing:defer:contentView:] + 1047
        5 AppKit 0x00007ff811a3fe72 -[NSWindow initWithContentRect:styleMask:backing:defer:] + 42
        6 libvtkRenderingOpenGL2-9.2.9.2.6.dy 0x0000000103c60d4d _ZN20vtkCocoaRenderWindow13CreateAWindowEv + 1859
        7 libvtkRenderingOpenGL2-9.2.9.2.6.dy 0x0000000103cd1c61 _ZN21vtkOpenGLRenderWindow5StartEv + 31
        8 libvtkRenderingOpenGL2-9.2.9.2.6.dy 0x0000000103c6137b _ZN20vtkCocoaRenderWindow5StartEv + 15
        9 libvtkRenderingCore-9.2.9.2.6.dylib 0x000000010c049f5d _ZN15vtkRenderWindow6RenderEv + 169
        10 libvtkRenderingOpenGL2-9.2.9.2.6.dy 0x0000000103cd3d27 _ZN21vtkOpenGLRenderWindow6RenderEv + 73
        11 genVTKimages 0x000000010005e33f _ZN8swiftLib14testVTKDataVizE15vtkSmartPointerI15vtkRenderWindowERNSt3__16vectorIS0_I11vtkPolyDataENS3_9allocatorIS6_EEEESA_PNS4_IdNS7_IdEEEEmmPNS3_12basic_stringIcNS3_11char_traitsIcEENS7_IcEEEE + 2191
        12 genVTKimages 0x000000010005f115 _ZN8swiftLib14testVTKDataVizE15vtkSmartPointerI15vtkRenderWindowES0_I11vtkPolyDataES4_PNSt3__16vectorIdNS5_9allocatorIdEEEEmmPNS5_12basic_stringIcNS5_11char_traitsIcEENS7_IcEEEE + 437
        13 genVTKimages 0x000000010005d751 _ZN8swiftLib14testVTKDataVizE15vtkSmartPointerI15vtkRenderWindowES0_I11vtkPolyDataES0_I9vtkPointsEPNSt3__16vectorIdNS7_9allocatorIdEEEEmmPNS7_12basic_stringIcNS7_11char_traitsIcEENS9_IcEEEE + 209
        14 genVTKimages 0x000000010005d5ff _ZN8swiftLib17dataVizComponents11writeOutImgENSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE15vtkSmartPointerI15vtkRenderWindowE + 143
        15 genVTKimages 0x000000010005d992 _ZN8swiftLib17dataVizComponents11writeOutImgE15vtkSmartPointerI15vtkRenderWindowE + 98
        16 genVTKimages 0x0000000100041e15 main + 7237
        17 dyld 0x00007ff80e5fc41f start + 190

```

3

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 11:06am UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/8 "2024-03-07T11:06:53Z")

</div>

Can you, please, share the C++ code of your test?

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 5:38pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/9 "2024-03-07T17:38:42Z")

</div>

Here it is, as an MRE. Note that the problem persists even if, as here, the vtkRenderWindow is rendering a blank scene. The preprocessor directives are to quickly verify the issue exists whether one vtkRenderWindow is instantiated for the entire loop and passed in, or within the looped function.

```auto
#include <sstream>
#include <vtkPNGWriter.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>
#include <vtkWindowToImageFilter.h>

// only turn one of these on at a time
//#define ONE_RENDERER // instantiate vtkRenderWindow outside the loop and pass into fcn
#define MANY_RENDERERS // instantiate vtkRenderWindow inside fcn

void testVTKDataViz(
#ifdef ONE_RENDERER
    vtkSmartPointer<vtkRenderWindow> renWin,
#endif
    std::string OPpath) {
        
#ifdef MANY_RENDERERS
        vtkNew<vtkRenderWindow> renWin;
        renWin->OffScreenRenderingOn();
#endif
        renWin->Render();
        
        vtkNew<vtkWindowToImageFilter> imgf;
        imgf->SetInput(renWin);
        imgf->SetInputBufferTypeToRGB();
        imgf->Update();
        
        vtkNew<vtkPNGWriter> wr;
        wr->SetFileName(OPpath.c_str());
        wr->SetInputConnection(imgf->GetOutputPort());
        wr->Write();
        
#ifdef MANY_RENDERERS
        renWin->Finalize();
#endif
}

int main() {

#ifdef ONE_RENDERER
        auto renWin = vtkSmartPointer<vtkRenderWindow>::New();
        renWin->OffScreenRenderingOn();
#endif
        std::string test_dir = "./imgDump";
        
        for (size_t ii=0; ii<1500; ii++) {
                std::stringstream ssPath;
                ssPath << test_dir << "/sphere_" << ii << ".png";
                std::cout << ssPath.str() << std::endl;
#ifdef MANY_RENDERERS
                testVTKDataViz(ssPath.str());
#endif
#ifdef ONE_RENDERER
                testVTKDataViz(renWin, ssPath.str());
                renWin->Finalize();
#endif
        }
        
        return EXIT_SUCCESS;
}

```

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 6:19pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/10 "2024-03-07T18:19:05Z")

</div>

Does the crash occur with `ONE_RENDERER` or `MANY_RENDERERS`?

All those `#define`s are obfuscating the code.

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 6:22pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/11 "2024-03-07T18:22:07Z")

</div>

It occurs in either scenario, that’s why I included them.

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 9:16pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/12 "2024-03-07T21:16:46Z")

</div>

Ok. Can you, please, post the simpler (enabled by `ONE_RENDERER`) one?

Thank you

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 9:20pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/13 "2024-03-07T21:20:37Z")

</div>

Sure:

```auto
#include <sstream>
#include <vtkPNGWriter.h>
#include <vtkRenderWindow.h>
#include <vtkSmartPointer.h>
#include <vtkWindowToImageFilter.h>

void testVTKDataViz(ER
    vtkSmartPointer<vtkRenderWindow> renWin,
    std::string OPpath) {
        
        renWin->Render();
        
        vtkNew<vtkWindowToImageFilter> imgf;
        imgf->SetInput(renWin);
        imgf->SetInputBufferTypeToRGB();
        imgf->Update();
        
        vtkNew<vtkPNGWriter> wr;
        wr->SetFileName(OPpath.c_str());
        wr->SetInputConnection(imgf->GetOutputPort());
        wr->Write();
        
}

int main() {

        auto renWin = vtkSmartPointer<vtkRenderWindow>::New();
        renWin->OffScreenRenderingOn();
        std::string test_dir = "./imgDump";
        
        for (size_t ii=0; ii<1500; ii++) {
                std::stringstream ssPath;
                ssPath << test_dir << "/sphere_" << ii << ".png";
                std::cout << ssPath.str() << std::endl;R
                testVTKDataViz(renWin, ssPath.str());
                renWin->Finalize();
        }
        
        return EXIT_SUCCESS;
}

```

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 9:47pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/14 "2024-03-07T21:47:20Z")

</div>

If you look into the code of `vtkWindowToImageFilter`’s `SetInput()` method:

```cpp
void vtkWindowToImageFilter::SetInput(vtkWindow* input)
{
  if (input != this->Input)
  {
    if (this->Input)
    {
      this->Input->UnRegister(this);
    }
    this->Input = input;
    if (this->Input)
    {
      this->Input->Register(this);
    }
    this->Modified();
  }
}

```

Notice the `vtkObjectBase::Register()` method which, in the end, prevents the instance from being deallocated once its smart pointer goes out of the scope, hence the “memory leak”. You need to call `imgf->SetInput(nullptr)` to un-register the instance with the `renWin` object before leaving the scope of `testVTKDataViz()`. The way your test is coded, getting that VTK warning is expected.

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 10:23pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/15 "2024-03-07T22:23:07Z")

</div>

Thanks for the suggestion. I tried it and am still having the same issue. Sequential calls to imgf-\>GetInput() before and after imgf-\>SetInput(nullptr) result in the following:

```auto
0x7faaebc04080
0x0

```

This seemingly confirms the vtkRenderWindow has been released by the vtkWindowToImageFilter. However, the memory problem remains. For good measure I tried also to SetInputConnection(nullptr) on the vtkPNGWriter, but no effect.

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 10:29pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/16 "2024-03-07T22:29:58Z")

</div>

Make sure you pass the null pointers while still inside the `testVTKDataViz()` function:

```cpp
void testVTKDataViz(ER
    vtkSmartPointer<vtkRenderWindow> renWin,
    std::string OPpath) {
        
        renWin->Render();
        
        vtkNew<vtkWindowToImageFilter> imgf;
        imgf->SetInput(renWin);
        imgf->SetInputBufferTypeToRGB();
        imgf->Update();
        
        vtkNew<vtkPNGWriter> wr;
        wr->SetFileName(OPpath.c_str());
        wr->SetInputConnection(imgf->GetOutputPort());
        wr->Write();

        imgf->SetInput(nullptr);
        wr->SetInputConnection(nullptr);
        
}

```

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 10:32pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/17 "2024-03-07T22:32:02Z")

</div>

Yes, they’re inside the `testVTKDataViz()` function.

---

<div class="post-metadata">

**Author:** ![Paulo\_Carvalho](https://discourse.vtk.org/user_avatar/discourse.vtk.org/paulo_carvalho/32/370_2.png) [@Paulo\_Carvalho](https://discourse.vtk.org/u/Paulo_Carvalho)\
**Post date:** [March 7, 2024, 10:40pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/18 "2024-03-07T22:40:38Z")

</div>

Since you already have a simple code that reproduces the issue, please, report a bug here: [https://gitlab.kitware.com/vtk/vtk/-/issues](https://gitlab.kitware.com/vtk/vtk/-/issues)

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 10:56pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/19 "2024-03-07T22:56:29Z")

</div>

I’m attempting to report it but keep getting flagged as spam. I’ll wait an hour or so then try again.

---

<div class="post-metadata">

**Author:** ![Zachary\_Stamler](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zachary_stamler/32/8581_2.png) [@Zachary\_Stamler](https://discourse.vtk.org/u/Zachary_Stamler)\
**Post date:** [March 7, 2024, 11:03pm UTC](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612/20 "2024-03-07T23:03:57Z")

</div>

Ok, done.

[Next page](https://discourse.vtk.org/t/vtkrenderwindow-memory-leak/10612.md?page=2)