Changing “cuda_compile_and_embed” to "embed_ptx"

[LCM1999]

I'm trying to upgrade the owl and optix versions in ExaBricks for some experience, I think I'm close to achieving this，however, a problem occurred after I modified the following code:
Change from
cuda_compile_and_embed( ptxCode programs/exabrick.cu )
to
embed_ptx( OUTPUT_TARGET ptxCode PTX_LINK_LIBRARIES owl::owl SOURCES exabrick.cu )
and I followed https://github.com/owl-project/owl/issues/136's suggestion, modified the variable for the ptx code to
extern "C" const char exabrick[];
when I build it, I got
[build] OptixRenderer.cpp.obj : error LNK2001: Unresolved external symbols exabrick.
Then I tried to check what's wrong with ptxCode by message(STATUS "PTX code embedded in target: ${ptxCode}") and the result is empty.

My environment:
cuda version: v12.6
optix 7.7
owl version: pull from master branch
device: rtx 4070ti
os: windows11

Could you give me some advice? Thanks a lot.

[szellmann]

Hi,
my blind guess is you're building the embedded PTX target, but not linking with it? Which would be fixed with a target_link_libraries(... ptxCode).

Can I ask which version of ExaBricks this is on? We haven't maintained the sample code in the while, but significant parts have moved to this project, which is also better maintained (CMake-wise..): https://github.com/owl-project/owlExaStitcher/tree/main (see {model|sampler}/ExaBricks.xxx).

[LCM1999]

Thanks a lot for your reply so quickly and your awesome work!

In the original CMakelists. ptxCode was added as exaViewer‘s source code
`
add_executable(exaViewer
glutViewer/Camera.cpp
glutViewer/FlyMode.cpp
glutViewer/InspectMode.cpp
glutViewer/OWLViewer.cpp
exa/viewer.cpp
exa/TriangleMesh.cpp
exa/ScalarField.cpp
exa/Config.cpp
exa/OptixRenderer.cpp
exa/ExaBricks.cpp
exa/Regions.cpp
exa/Texture.cpp
exa/ColorMapper.cpp
${ptxCode}
)
target_link_libraries(exaViewer
glui_static
owl::owl

${CUDA_LIBRARIES}
${OWL_LIBRARIES}
${OWL_VIEWER_LIBRARIES}
${TBB_LIBRARIES}
${GLUT_LIBRARIES}
${OPENGL_LIBRARIES}
${CMAKE_DL_LIBS}
)
`
I tried linking ptxCode as your advice, but it doesn't work, as I mentioned before it seems that the ptxCode is empty(? maybe the way I check it is wrong?).

I'm working on this version https://github.com/owl-project/owlExaBrick, I will immediately try ExaStitcher.

Whatever, it seems that the ExaStitcher could be a better repo to go on.

Thanks for your help again.

[szellmann]

I think the issue is that you use ptxCode as a variable (${ptxCode}) while in fact it is a target. Used as a variable, it would naturally be empty/not set, as that variable doesn't exist. So I think it should just be fixed by doing

target_link_libraries(exaViewer
glui_static
owl::owl
ptxCode -> add here

${CUDA_LIBRARIES}
${OWL_LIBRARIES}
${OWL_VIEWER_LIBRARIES}
${TBB_LIBRARIES}
${GLUT_LIBRARIES}
${OPENGL_LIBRARIES}
${CMAKE_DL_LIBS}
)

but not using ${...} syntax.

This has changed in OWL, embed_ptx generates a real cmake target these days, similar to the glui_static or owl::owl that you see. Which can be a bit confusing. Back in the days it generated C source code directly that you would compile as part of the host project, but not anymore, these days the PTX code gets linked.