Gabriele Cosmo
98 lines
2.6 KiB
Markdown
98 lines
2.6 KiB
Markdown
\page Examplevtk Example vtk
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This example demonstrates VTK visualisation driver. The code is based on
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the basic/B1 example, although the geometry has been modified. The physical
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example is a concerete dump, so a cuboid with a cylindrical hole removed.
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VTK is a graphical pipeline (https://book.vtk.org/en/latest/VTKBook/04Chapter4.html#pipeline-design-and-implementation)
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based renderer.
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VTK has some visualisation commands which are not applicable to all viewers,
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which currently include cutters, clippers and geometry overlays. The VTK commands
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are in vtk.mac and you can explore apply different VTK only commands.
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A- VISUALISATION
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================
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This example is really for demonstration of VTK and so the easiest way to start with
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```
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% G4VIS_DEFAULT_DRIVER=VtkQt ./exampleVtk
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```
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or
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```
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% G4UI_USE_TCSH=1 G4VIS_DEFAULT_DRIVER=VtkNative ./exampleVtk
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```
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The event loop for the UI can be blocked by the VtkNative window. So if input events
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are captured by VTK, then the easiest way to exit from the viewer is to hit the 'q' button,
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then you are returned to the shell UI. To restart interaction then issue the command
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```
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Idle> /vis/vtk/startInteractor
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```
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B- USER INTERFACES
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==================
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VTK can be used in conjunction with all UI systems. If a shell UI is used event loop for the UI can be blocked
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by the VtkNative window. So if input events are captured by VTK, then the easiest way to
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exit from the viewer is to hit the 'q' button, then you are returned to the shell UI.
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To restart interaction then issue the command
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```
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Idle> /vis/vtk/startInteractor
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```
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C- HOW TO RUN
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=============
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Starting with VTK
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```
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% G4VIS_DEFAULT_DRIVER=VtkQt ./exampleVtk
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```
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Executing VTK specific commands
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```
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Idle> /control/execute vtk.mac
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```
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There are various pipelines and the state of the pipelines can be
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displayed by issuing this command
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```
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/vis/vtk/printDebug
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```
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Pipelines can be switched during operation. This is performed by calling
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```
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/vis/vtk/set/polyhedronPipeline (append/tensor/bake/separate)
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```
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and then a subsequent
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```
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/vis/viewer/flush
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```
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There is significantly different performance between these pipelines. Append, tensor
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and bake are all designed for large models and high performance. Separate creates
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a pipeline for each polyhedron, each pipeline will ultimately end with a draw call.
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In general with modern pipelined shaders draw calls should be kept to a minimum.
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For debugging the VTK viewer it is possible to place a head up display (HUD) which
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gives key information on the viewer performance. The HUD is enabled by issuing
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```
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/vis/vtk/set/hud 1
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```
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Stewart Boogert
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7th November 2023
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