# \[Volume Rendering\] Rendering artifacts after window refresh and model hide/show operations in VTK 9.1.0

**URL:** https://discourse.vtk.org/t/volume-rendering-rendering-artifacts-after-window-refresh-and-model-hide-show-operations-in-vtk-9-1-0/16179
**Category:** Support
**Tags:** rendering, code
**Created:** [December 10, 2025, 9:45am UTC](https://discourse.vtk.org/t/volume-rendering-rendering-artifacts-after-window-refresh-and-model-hide-show-operations-in-vtk-9-1-0/16179 "2025-12-10T09:45:45Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![maomaolemon](https://discourse.vtk.org/user_avatar/discourse.vtk.org/maomaolemon/32/10388_2.png) [@maomaolemon](https://discourse.vtk.org/u/maomaolemon)
#### Post date: [December 10, 2025, 9:45am UTC](https://discourse.vtk.org/t/volume-rendering-rendering-artifacts-after-window-refresh-and-model-hide-show-operations-in-vtk-9-1-0/16179/1 "2025-12-10T09:45:45Z")

</div>

**Problem Description** :

I’m using `vtkOpenGLGPUVolumeRayCastMapper` to render volumetric data imported via `vtkImageImport`. The data source is a series of 128×128 CV\_8UC1 images, as implemented in my `ShowImageData()` function (code attached below). The initial render works correctly and produces acceptable results (Figure 1).

**Current Setup** :

- VTK Version: 9.1.0
- Data type: `CV_8UC1` images converted to vtkImageData

**Current Problem: Window Refresh Artifact and Hide/Show Artifact**  
After the initial successful rendering, when I refresh the 3D window by calling the same model generation function (`Refresh3DVolumeZoom()`), or when I hide the current volume model to display a different surface-rendered model and then show the original volume model again, the rendering quality degrades significantly (Figure 2). The volume appears darker with noticeable artifacts.  
Same function (`Refresh3DVolumeZoom()`) is called for both initial render and refresh, and no parameters are changed between calls.

**Code Snippets** :

```cpp
unsigned char *m_p3DVisualizationDataLumenZoomIn;
void ShowImageData()
{
	int frames = m_n3DFrames;
	int imSize = 128 * 128;
	for (int frameInd = 0; frameInd < frames; ++frameInd)
	{
		cv::Mat output, imgC = cv::Mat::zeros(128,128,CV_8UC1);
		......
		......
		memcpy(m_p3DVisualizationDataLumenZoomIn + frameInd * imSize, imgC.data, imSize * sizeof(char));
	}	

	double sizeV = 700;
	double size3D = 128;
	double vol = sizeV / size3D;
	m_p3DImageImportZoom->SetDataSpacing(m_d3DSpaceXY * vol, m_d3DSpaceXY * vol, m_d3DSpaceZ);
	m_p3DImageImportZoom->SetDataOrigin(0, 0, 0);
	m_p3DImageImportZoom->SetWholeExtent(0, 127, 0, 127, 0, frames - 1);
	m_p3DImageImportZoom->SetDataExtentToWholeExtent();
	m_p3DImageImportZoom->SetDataScalarTypeToUnsignedChar();
	m_p3DImageImportZoom->SetNumberOfScalarComponents(1);
	m_p3DImageImportZoom->RemoveAllInputs();
	m_p3DImageImportZoom->SetImportVoidPointer(m_p3DVisualizationDataLumenZoomIn);
	m_p3DImageImportZoom->Update();

	m_p3DRenWin->Render();
}

void Refresh3DVolumeZoom()
{
	m_p3DVolumeMapper1 = vtkSmartPointer<vtkOpenGLGPUVolumeRayCastMapper>::New();
	m_p3DVolume1->SetMapper(m_p3DVolumeMapper1);

	m_p3DVolumeProperty1->SetInterpolationTypeToLinear();
	m_p3DVolumeProperty1->ShadeOn();
	m_p3DVolumeProperty1->SetAmbient(1.2);
	m_p3DVolumeProperty1->SetDiffuse(0.2);
	m_p3DVolumeProperty1->SetSpecular(0.1);

	m_p3DGaussian1->SetInputConnection(m_p3DImageImportZoom->GetOutputPort());
	m_p3DGaussian1->SetDimensionality(3);
	m_p3DGaussian1->SetRadiusFactor(1.0);
	m_p3DGaussian1->SetStandardDeviation(1.0);
	m_p3DGaussian1->Update();
	m_p3DImageImportZoom->GetOutput()->ShallowCopy(m_p3DGaussian1->GetOutput());

	m_p3DVolumeMapper1->SetBlendModeToComposite();
	m_p3DVolumeMapper1->SetInputData(m_p3DImageImportZoom->GetOutput());
	m_p3DVolumeMapper1->SetSampleDistance(0.0005);
	m_p3DVolumeMapper1->AutoAdjustSampleDistancesOff();

	m_p3DVolumeComposite1->RemoveAllPoints();
	m_p3DVolumeComposite1->AddPoint(0, 0.0);
	m_p3DVolumeComposite1->AddPoint(10, 0.0);
	m_p3DVolumeComposite1->AddPoint(11, 0.3);
	m_p3DVolumeComposite1->AddPoint(30, 0.5);
	m_p3DVolumeComposite1->AddPoint(50, 0.7);
	m_p3DVolumeComposite1->AddPoint(70, 0.9);
	m_p3DVolumeComposite1->AddPoint(128, 0.99);
	m_p3DVolumeComposite1->AddPoint(255, 1.0);

	m_p3DVolumeGradient1->RemoveAllPoints();
	m_p3DVolumeGradient1->AddPoint(0, 1.0);
	m_p3DVolumeGradient1->AddPoint(1, 1.0);
	m_p3DVolumeGradient1->AddPoint(1.1, 1.0);
	m_p3DVolumeGradient1->AddPoint(255, 1.0);

	m_p3DVolumeColor1->RemoveAllPoints();
	m_p3DVolumeColor1->AddRGBPoint(0, 0.0, 0.0, 0.0);
	m_p3DVolumeColor1->AddRGBPoint(10, 0.0, 0.0, 0.0);
	for (int i = 11; i <= 255; i++) {
		m_p3DVolumeColor1->AddRGBPoint(i, m_vSepiaMap[i], m_vSepiaMap[i + 256], m_vSepiaMap[i + 512]);
		//m_vSepiaMap is an immutable constant value.
	}

	double* dataSpace = m_p3DImageImportZoom->GetDataSpacing();
	int* dataExtent = m_p3DImageImportZoom->GetDataExtent();
	m_p3DVolume1->SetOrigin((dataExtent[1] + 1) * dataSpace[0] / 2.0, (dataExtent[3] + 1) * dataSpace[1] / 2.0, 0);
	m_p3DVolumeProperty1->Modified();
	m_p3DVolumeMapper1->Modified();
	m_p3DVolume1->Modified();

	m_p3DSurfRenderer->SetUseDepthPeeling(1);
	m_p3DSurfRenderer->ResetCameraClippingRange();
	m_p3DRenWin->Render();
}

```

**Screenshots** :  
Image1:

 ![image](https://discourse.vtk.org/uploads/default/original/2X/1/138593150b243b131b208827762e8544796db770.png)  
Image2:  
 ![image](https://discourse.vtk.org/uploads/default/original/2X/6/6ddd4f958c7503aef02a54188fec1d9814484326.png)

**Thank you for any guidance!**