[Development] QSG render thread crashes during volumetric rendering

[Cartik Sharma]

Hello,

I'm trying to do volumetric rendering with VTK using the
QVTKFramebufferObject class from
https://gist.github.com/nocnokneo/c3fb01bb7ecaf437f7d6

Essentially this is a class based on QQuickFramebufferObject and over rides
rendering with certain presets for OpenGL states.

It works well for images and 3D objects but crashes the QSG render thread
during render calls from vtkFixedPointVolumeRayCastMapper. I need help
debugging the crash and fixing this error. (please refer crash report in
render_crash.txt)

Best regards,
Cartik
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Thread 7 Crashed:: QSGRenderThread

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: EXC_I386_GPFLT

0   com.apple.GeForceGLDriver     	0x000000020032d729 gldBlitFramebufferData + 162529
1   com.apple.GeForceGLDriver     	0x0000000200324d14 gldBlitFramebufferData + 127180
2   com.apple.GeForceGLDriver     	0x00000002002d8e87 gldRestoreTextureData + 779309
3   com.apple.GeForceGLDriver     	0x00000002002d80c3 gldRestoreTextureData + 775785
4   com.apple.GeForceGLDriver     	0x00000002001d66e2 0x200000000 + 1926882
5   com.apple.GeForceGLDriver     	0x0000000200305e8e gldBlitFramebufferData + 582
6   libGPUSupport.dylib           	0x00000001470e9a6d gldUpdateDrawFramebuffer + 108
7   GLEngine                      	0x0000000146e72e55 gleUpdateDrawFramebufferState + 556
8   GLEngine                      	0x0000000146d60369 glClear_Exec + 256
9   QtQuick                       	0x00000001114e8f95 QSGBatchRenderer::Renderer::renderBatches() + 533
10  QtQuick                       	0x00000001114ea557 QSGBatchRenderer::Renderer::render() + 2343
11  QtQuick                       	0x00000001114f70b0 QSGRenderer::renderScene(QSGBindable const&) + 352
12  QtQuick                       	0x00000001114f6f3c QSGRenderer::renderScene() + 28
13  QtQuick                       	0x000000011150620b QSGRenderContext::renderNextFrame(QSGRenderer*, unsigned int) + 107
14  QtQuick                       	0x0000000111542179 QQuickWindowPrivate::renderSceneGraph(QSize const&) + 649
15  QtQuick                       	0x000000011151f521 QSGRenderThread::syncAndRender() + 289
16  QtQuick                       	0x000000011151f968 QSGRenderThread::run() + 200
17  QtCore                        	0x00000001129f5332 QThreadPrivate::start(void*) + 338
18  libsystem_c.dylib             	0x00007fff89aea772 _pthread_start + 327
19  libsystem_c.dylib             	0x00007fff89ad71a1 thread_start + 13