double GetFirstElement(vtkMatrix4x4 mat*) {
return mat->GetElement(0,0);
}
```
I’m on Mac 10.14.5, on the master branch of VTK. Apologies if I’m missing something simple, and thanks in advance for any help!
Best, and thanks,
–Davis
---
### Author:  [@Ron84](https://discourse.vtk.org/u/Ron84)
#### Post date: [July 7, 2019, 10:49am UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/2 "2019-07-07T10:49:05Z")
The common pattern for VTK and any other package is this:
```auto
find_package(VTK REQUIRED #[[COMPONENTS vtkFiltersSources vtkIOLegacy ... NO_MODULE]])
if(VTK_FOUND)
include(${VTK_USE_FILE}) # this is important
add_library(${PROJECT_NAME} #[[...]])
target_link_libraries(${PROJECT_NAME} ${VTK_LIBRARIES})
endif()
```
---
### Author:  [@sudomakeinstall](https://discourse.vtk.org/u/sudomakeinstall)
#### Post date: [July 7, 2019, 5:49pm UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/3 "2019-07-07T17:49:05Z")
Ron–
Thanks for your response. I had previously been using `include(${VTK_USE_FILE})`, but upon updating to the master branch I began getting an error about there being an incorrect number of arguments to the include function. Is `${VTK_USE_FILE}` no longer being set? I gather from Dr. Lorensen’s examples on github [1] that this functionality has somehow been replaced by `vtk_module_autoinit` in recent versions of VTK.
Ultimately, I was able to get it all working (building a library that depends on VTK, and then building an executable which depends both on VTK and on my library) with something similar to this:
```
cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
project(dv-commandline-utils)
find_package(VTK REQUIRED)
include_directories("includes/")
file(GLOB SRC src/*.cxx)
add_library(dv-utils-lib ${SRC})
target_link_libraries(dv-utils-lib ${VTK_LIBRARIES})
add_executable(dv-visualize-meshes dv-visualize-meshes.cxx)
target_link_libraries(dv-visualize-meshes ${VTK_LIBRARIES} dv-utils-lib)
vtk_module_autoinit(
TARGETS dv-visualize-meshes
MODULES ${VTK_LIBRARIES}
)
```
Thanks very much for your help,
–Davis
---
### Author:  [@Ron84](https://discourse.vtk.org/u/Ron84)
#### Post date: [July 7, 2019, 8:35pm UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/4 "2019-07-07T20:35:40Z")
My mistake. But this is the old problem with VTK. Nothing is well documented…
---
### Author:  [@sudomakeinstall](https://discourse.vtk.org/u/sudomakeinstall)
#### Post date: [July 7, 2019, 8:41pm UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/5 "2019-07-07T20:41:33Z")
Ron–
No worries–your response nonetheless pointed me down the right path. At least what the ITK/VTK echosystem occasionally lacks in documentation, it makes up for with an active and supportive community!
Best, and thanks again,
–Davis
---
### Author:  [@amaclean](https://discourse.vtk.org/u/amaclean)
#### Post date: [July 8, 2019, 4:05am UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/6 "2019-07-08T04:05:58Z")
Since you are using the VTK Master, try using: `Utilities/Maintenance/FindNeededModules.py`.
This will produce an output something like this that only lists the modules needed by your library:
```auto
find_package(VTK
COMPONENTS
CommonColor
CommonCore
CommonDataModel
CommonTransforms
FiltersGeneral
FiltersModeling
FiltersSources
IOGeometry
IOLegacy
IOPLY
IOXML
RenderingCore
# These modules are suggested since they implement an existing module.
# Uncomment those you need.
# InteractionStyle # implements VTK::RenderingCore
# RenderingFreeType # implements VTK::RenderingCore
# RenderingOpenGL2 # implements VTK::RenderingCore
)
```
that you can drop into your CMake file.
Then …
**Note:** _I haven’t tried this!_.
```auto
add_library(dv-utils-lib MACOSX_BUNDLE ${SRC} )
target_link_libraries(dv-utils-lib PRIVATE ${VTK_LIBRARIES})
# vtk_module_autoinit is needed
vtk_module_autoinit(
TARGETS dv-utils-lib
MODULES ${VTK_LIBRARIES}
)
```
---
### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [July 8, 2019, 10:42am UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/7 "2019-07-08T10:42:35Z")
> [@Ron84](#):
>
> But this is the old problem with VTK. Nothing is well documented…
ParaView is in its release cycle and has gotten documentation love. VTK will get the same before the release happens. There’s developer-level documentation, but user-level docs are missing right now.
---
### Author:  [@sudomakeinstall](https://discourse.vtk.org/u/sudomakeinstall)
#### Post date: [July 10, 2019, 3:28pm UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/8 "2019-07-10T15:28:55Z")
Hey @amaclean very cool script! I’ve never known the right way to go about figuring out which components are needed.
I tried running it on my project, and it gave me the following:
```
find_package(VTK
COMPONENTS
CommonCore
CommonDataModel
CommonMath
CommonTransforms
FiltersCore
FiltersExtraction
FiltersGeneral
FiltersModeling
FiltersSources
IOGeometry
IOImage
IOLegacy
ImagingColor
InteractionImage
InteractionWidgets
RenderingAnnotation
RenderingCore
RenderingOpenGL2
RenderingVolumeOpenGL2
# These modules are suggested since they implement an existing module.
# Uncomment those you need.
# InteractionStyle # implements VTK::RenderingCore
# RenderingFreeType # implements VTK::RenderingCore
# RenderingGL2PSOpenGL2 # implements VTK::RenderingOpenGL2
)
```
Looks good, but now it unfortunately can’t find my Qt headers. I expect that it’s related to the rendering core (see commented at the bottom of the script), but I’ve tried uncommenting each in turn, with no luck. Is there something special I need to do to get this working with Qt?
And again, thanks so much for your help.
Best,
–Davis
---
### Author:  [@amaclean](https://discourse.vtk.org/u/amaclean)
#### Post date: [July 10, 2019, 11:23pm UTC](https://discourse.vtk.org/t/building-a-library-which-depends-on-vtk-headers-not-found/1298/9 "2019-07-10T23:23:09Z")
You will have to manually add other components. Tthe script only looks for vtk includes that start with lower-case vtk e.g. `vtkSmartPointer.h`