Add a new optional command to export textured mesh to a USD format

[serguei-k]

Description

Add a new optional command to export textured mesh to a USD format.

Features list

• Add new command exportUSD to export mesh and textures to USD
• Add a simple Materials class to capture the small subset of material properties and associated textures that is supported by texturing pipeline
• Update texturing pipeline to make use of new material class
• Fix bug in normal computation (checking for NaN)
• Fix bug in loading mesh data not setting the correct number of atlases and materials used
• Fix bug in loading mesh data using incorrect material ID due to default material
• Add option to merge coincident vertices when loading meshes with multiple materials

[serguei-k]

Was getting 0 normals, found this small issue

[serguei-k]

nmtls property was never set, so when loading an asset with materials the number of atlases wasn't being set correctly.

[serguei-k]

Added as new method for clarity, could edit existing load method instead.

[serguei-k]

moved after texture generation for consistency in logic

[simogasp]

Thanks for your contribution!

Would you mind adding the cmake instructions to install the dependency (https://github.com/PixarAnimationStudios/USD I guess) in the main CMakeLists.txt through ExternalProject_Add, as we did for all the others https://github.com/alicevision/AliceVision/blob/develop/CMakeLists.txt#L10?
you can declare a

option(AV_BUILD_USD "Enable building an embedded USD library" ON)
...
message(STATUS "AV_BUILD_USD: ${AV_BUILD_USD}")

and

if(AV_BUILD_USD)
set(USD_TARGET usd)
ExternalProject_Add(${USD_TARGET}
       .... # see others for examples
       DEPENDS ${TBB_TARGET} ${BOOST_TARGET}. # these seem to be the only dependencies?
       )
set(USD_CMAKE_FLAGS -DUSD_DIR:PATH=${CMAKE_INSTALL_PREFIX}/<where to find the USDConfig.cmake>)
endif()

and add USD_CMAKE_FLAGS at the very end around line 1059

set(AV_DEPS
  ${ZLIB_TARGET}
 .....
  ${CLP_TARGET}
  ${USD_TARGET}       # <<<
)

if(AV_BUILD_ALICEVISION)
ExternalProject_Add(aliceVision
       PREFIX ${CMAKE_CURRENT_SOURCE_DIR}
       .
       .
       .
            ${ZLIB_CMAKE_FLAGS}
            ${ASSIMP_CMAKE_FLAGS}
            ${EIGEN_CMAKE_FLAGS}
            .
            .
            ${FLANN_CMAKE_FLAGS}
            ${PCL_CMAKE_FLAGS}
            ${USD_CMAKE_FLAGS}       # <<<
            -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR> <SOURCE_DIR>
       DEPENDS ${AV_DEPS}
       )
endif()

[fabiencastan]

The error in the CI is unrelated to your PR. It's an issue in the CI env since we switched to C++17.

[serguei-k]

Thanks for your contribution!

Would you mind adding the cmake instructions to install the dependency (https://github.com/PixarAnimationStudios/USD I guess) in the main CMakeLists.txt through ExternalProject_Add, as we did for all the others https://github.com/alicevision/AliceVision/blob/develop/CMakeLists.txt#L10? you can declare a

Thanks for the note, added the optional build step for USD.

[serguei-k]

Hi guys, just a heads up that I will be starting a new job next week that will prevent me from working on oss code, so if you would like me to make any changes please let me know :)

[mugulmd]

Hi guys, just a heads up that I will be starting a new job next week that will prevent me from working on oss code, so if you would like me to make any changes please let me know :)

I've just started building your branch for testing, I'll let you know if I spot something 😉

[simogasp]

Hi guys, just a heads up that I will be starting a new job next week that will prevent me from working on oss code, so if you would like me to make any changes please let me know :)

I was wondering whether it could be better to move the part of the code that actually saves the mesh into a USD file (i.e. the code from main_exportUSD) directly into the library part, so that it could be used everywhere else if one wants to save a mesh in that format. This would also allow the meshroom user to save the mesh directly in USD format in the texturing node, without going through another node.

In practice, we could refactor the code and modify the current Mesh::save() method so that once it detects the format

void Mesh::save(const std::string& filepath)
{
    const std::string fileTypeStr = boost::filesystem::path(filepath).extension().string().substr(1);
    const EFileType fileType = mesh::EFileType_stringToEnum(fileTypeStr);

and then calls another save method accordingly: e.g. saveUSD() method that contains the code you already wrote for the main_exportUSD or e.g. saveAssimp() that saves the mesh using Assimp (i.e. the code of the current Mesh::save() method).

And, obviously, we can modify all the relevant enum such as mesh::EFileType accordingly to add the USD format.

What do you think?

[mugulmd]

Okay so building AliceVision with USD is not an easy task since there are conflicts with TBB versions, so the fact that this is optional is definitely a plus 😅

I did some testing with textured meshes generated with the photogrammetry pipeline and visualized them in usdview, everything seems to be working fine.

Great job, thanks for the contribution!