Customizing Shader Object Filenames in CMake with VS_SHADER_OBJECT_FILE_NAME

VS_SHADER_OBJECT_FILE_NAME

Introduced in CMake version 3.12, this property allows you to explicitly specify the filename for the compiled shader object file generated from a HLSL (High-Level Shading Language) source file during the build process.

Purpose

• Conflict Resolution
  If you have multiple HLSL source files with potentially conflicting default names for their compiled object files, you can use VS_SHADER_OBJECT_FILE_NAME to assign unique names and avoid overwriting issues.
• Customization
  By overriding the default naming convention, you gain control over the output filename for shader object files. This can be useful for organizing your project structure or integrating with specific build systems that have naming requirements.

Usage

1. Target Configuration
   Within your CMakeLists.txt file, locate the target that compiles your HLSL source file. This target could be a custom command or a built-in generator like shader.

set_source_files_properties(
    <HLSL_source_file>  # Path to your HLSL source file
    PROPERTIES
        VS_SHADER_OBJECT_FILE_NAME "<output_filename>.<object_extension>"
)

• The <object_extension> will typically be .fxobj for DirectX projects on Windows or a platform-specific extension depending on your target graphics API and compiler.
• Set <output_filename> to the desired name for the compiled object file (without the extension).
• Replace <HLSL_source_file> with the actual path to your HLSL source file.

Example

set(HLSL_SOURCE_FILE "path/to/my_shader.hlsl")

set_source_files_properties(
    ${HLSL_SOURCE_FILE}
    PROPERTIES
        VS_SHADER_OBJECT_FILE_NAME "custom_shader"  # Output filename without extension
)

In this example, the HLSL source file my_shader.hlsl will be compiled, and the resulting object file will be named custom_shader.<object_extension> (e.g., custom_shader.fxobj on Windows).

Benefits

• Reduced risk of naming conflicts that could lead to build errors.
• Improved organization and clarity in your project structure, especially when dealing with multiple HLSL files.

---

# Define the directory containing your HLSL source files
set(HLSL_SOURCE_DIR "path/to/your/hlsl/files")

# List of HLSL source files (assuming they are all in the same directory)
set(HLSL_SOURCES
    vert_shader.hlsl
    frag_shader.hlsl
    geometry_shader.hlsl  # Optional, if you're using a geometry shader
)

# Compile each HLSL source file with a unique object filename
foreach(HLSL_SOURCE ${HLSL_SOURCES})
    get_filename_component(HLSL_FILENAME_WO_EXT ${HLSL_SOURCE} NAME_WE)

    # Set VS_SHADER_OBJECT_FILE_NAME with a custom naming convention
    set_source_files_properties(
        ${HLSL_SOURCE_DIR}/${HLSL_SOURCE}
        PROPERTIES
            VS_SHADER_OBJECT_FILE_NAME "${HLSL_FILENAME_WO_EXT}_obj"
    )

    # Add the HLSL source file to the target (assuming a custom target)
    add_custom_command(
        TARGET my_shader_target  # Replace with your actual target name
        OUTPUT_FILE "${HLSL_SOURCE_DIR}/${HLSL_FILENAME_WO_EXT}_obj"  # Output object file
        COMMAND fxc
            /T vs_5_0  # Shader model (adjust as needed)
            /E ${HLSL_FILENAME_WO_EXT}  # Entry point function name
            /Fo "${HLSL_SOURCE_DIR}/${HLSL_FILENAME_WO_EXT}_obj"  # Output object filename
        WORKING_DIRECTORY "${HLSL_SOURCE_DIR}"
        DEPENDS "${HLSL_SOURCE_DIR}/${HLSL_SOURCE}"
    )
endforeach()

1. HLSL Source Directory
   Define the HLSL_SOURCE_DIR variable to point to the directory containing your HLSL source files.
2. HLSL Source List
   Create a list named HLSL_SOURCES containing the names of your HLSL files (assuming they're all in the same directory).
3. Iterate Over Sources
   The foreach loop iterates through each HLSL source file in the list.
4. Extract Filename
   Use get_filename_component to extract the filename without the extension and store it in HLSL_FILENAME_WO_EXT.
5. Set VS_SHADER_OBJECT_FILE_NAME
   Inside the loop, use set_source_files_properties to set the VS_SHADER_OBJECT_FILE_NAME property for the current HLSL source file. The output filename is constructed using "${HLSL_FILENAME_WO_EXT}_obj" to create a unique name with the .obj extension (replace with the appropriate extension for your target platform).
6. Custom Command
   A custom command is added to the target (replace my_shader_target with your actual target name). This command uses the fxc compiler (adjust the command and options based on your specific compiler and shader model requirements) to compile the HLSL source file and specify the output object filename using the previously set VS_SHADER_OBJECT_FILE_NAME.
7. Dependencies
   The custom command depends on the corresponding HLSL source file to ensure it's compiled first.

---

1. CMake's Default Naming Convention
   CMake typically generates object filenames based on the source filename and target properties. You can often rely on this default behavior for basic project structures.

2. Custom Target Properties
   

   • If you have a custom target that compiles your HLSL source files, you can set target-specific properties to influence the naming of generated files. Consult your build system's documentation for details on supported properties.

Choosing the Right Approach