MDL SDK 2026.0.0 (391700.996): 01 Jun 2026

ABI compatible with the MDL SDK 2026.0.0 (391700.996) binary release
(see https://developer.nvidia.com/mdl-sdk)

Added and Changed Features

• MDL 1.11 Language Specification

  • Updated version to 1.11.
  • Added enumeration type ::df::backscatter_modifier to modify backscattering behavior
    of microfacet BSDFs.
  • Added parameter uniform backscatter_modifier backscatter for the following BSDFs:
    • specular_bsdf
    • simple_glossy_bsdf
    • microfacet_beckmann_smith_bsdf
    • microfacet_ggx_smith_bsdf
    • microfacet_beckmann_vcavities_bsdf
    • microfacet_ggx_vcavities_bsdf
    • fresnel_factor
    • directional_factor
    • measured_curve_factor
    • measured_factor
    • fresnel_layer
    • color_fresnel_layer
    • custom_curve_layer
    • color_custom_curve_layer
    • measured_curve_layer
    • color_measured_curve_layer

• General

  • The recommended vcpkg version has been updated to git ID 7853666. This update includes
    GLEW 2.3.1 and various security fixes for dependencies.
  • Improved performance of IMdl_module::is_valid().
  • Added spectral rendering support. Refer to the MDL SDK Tutorial documentation
    ("Example for spectral rendering") for integration details.
    • New spectral color type: tct_spectral_sample.
    • New spectral shading state types: Shading_state_material_spectral and
      Shading_state_material_spectral_with_derivs.
    • BSDF/EDF data structures (Bsdf_sample_data, Bsdf_evaluate_data, etc.) are now
      templated on Target_code_color_mode to switch between RGB and spectral layouts.
    • New texture runtime functions for up-sampling from RGB to spectral.
    • New SDK compile-time constant MDL_DF_SPECTRAL_SAMPLES to select the number of
      spectral samples processed per call (default is 5). It can be overrided through
      the new CMake option MDL_DF_SPECTRAL_SAMPLES_OVERRIDE.
    • New backend option libbsdf_enable_spectral enables spectral code generation on backends.
    • Example runtimes and integrations for the native, HLSL, and GLSL backend.
    • Spectral evaluation operates at the BSDF/EDF level only; all input data (colors,
      textures, etc.) remain RGB, but the SDK provides built-in and custom means to upsample
      them to spectral samples per wavelength.
    • Refer to the MDL SDK Tutorial documentation ("Example for spectral rendering") for
      integration details.
  • The new CMake option MDL_BUILD_SEPARATE_DEBUG_INFO allows generating separate debug
    information in release builds.
  • The API reference documentation can now also be built with newer Doxygen versions,
    although the recommended version has been unchanged.
  • The thread-safety guarantees for transactions and database elements have been improved.
    See documentation on ITransaction for details.
  • The performance of internal accesses to database elements has been improved.
  • The unused interfaces Std_allocator and Default_allocator have been deprecated.
    Still available if MI_NEURAYLIB_DEPRECATED_17_0 is defined.
  • The support for MI_NEURAYLIB_DEPRECATED_15_0 has been removed.
  • The documentation for the ::base and ::nvidia::core_definitions modules has been
    converted to Markdown format.
  • Improved handling of I/O errors and invalid input in the OpenImageIO and DDS plugins.
  • Added the API component IExtension_api which allows to register custom IStruct and
    IEnum declarations.
  • Added support for Ninja as CMake generator on Windows.

• MDL Compiler and Backends

  • Added backend option libbsdf_enable_spectral to enable spectral support.
    When enabled, the BSDF data structures will use spectral sample types for IOR, BSDF,
    pdf, and albedo fields. The texture runtime was extended with spectral support
    functions, which can be left unimplemented (null pointers) if spectral mode is not
    used. In spectral mode, the native runtime expects Shading_state_material_spectral
    or Shading_state_material_spectral_with_derivs to be used, which contain a new field
    for the currently active wavelengths. Other backends may use alternative mechanisms to
    make the wavelengths available to the spectral support functions in the texture runtime.
  • Improved HLSL/GLSL code generation.
  • Added MDL_JIT_DISASM_FILE environment variable to dump native JIT disassembly to a
    file for debugging.
  • Changed alignment of texture results and matrices to 16-byte alignment.
  • Added glsl_include_for_api_types GLSL backend option to emit an include directive of
    the provided file name instead of the API types. This allows the use of custom API
    types with additional fields. If this option is used, the GL_GOOGLE_include_directive
    GLSL extension will be required.
  • Handle integer division overflow gracefully in constant folding. A new warning is
    issued: "integer overflow in expression (int)min <op> -1 of type int results in
    <res>"

• MDL Distiller and Baker

  • Improved distilling of rough transparent materials for the rtx_distiller target.
  • Added support for blending of bsdf() (as well as BSDFs converted to bsdf() like
    measured_bsdf()) for the rtx_distiller target.
  • Added support for emission mixing for the rtx_distiller target.

• MDL SDK examples

  • The df_native, df_vulkan, and dxr examples now demonstrate the new MDL SDK
    spectral rendering feature via the --spectral command-line option (default rendering
    remains RGB).
  • Example df_native:
    • Added support for evaluation of hair-BSDFs on an analytical cylinder.
  • Example df_native and dxr:
    • Gamma correction now clips values to avoid NaNs.
  • Example dxr:
    • Added command line option --load_plugin to load additional plugins like custom
      distiller plugins.
    • Added command-line option --show_camera. In the camera panel, it shows world-space
      position and focus (same convention as --camera).

• MDL Core examples

  • Clamp maximum path length to [2,100].
  • Example codegen:
    • Generate code also for volume.emission_intensity.
  • Example df_cuda:
    • Harmonized command-line options: -p is now the MDL path (i.e., --mdl_path),
      --camera is now the camera parameter (previously -p), and --help has been added.

Fixed Bugs

• General

  • Fixed detection of MaterialX for the vcpkg x64-windows triplet.
  • Fixed a rare build error in parallel builds on Windows for projects that embed a
    Windows resource file.
  • Fixed sentinel value of IImage::get_uv_tile_id() (was 2^32-1 instead of 2^64-1).
  • Fixed documentation regarding the sentinel value of methods returning mi::Uint64
    (was documented as -1 instead of ~0U).
  • Fixed a rare race condition related to the registration of struct categories and
    struct/enum types.
  • Fixed a rare crash/deadlock that can occur when committing or aborting a transaction
    in connection with multiple scopes.
  • Fixed corner cases for the assembly implementation of mi::base::Atom32 and the
    Linux/macOS variant of mi::base::Condition::timed_wait(), although no problems have
    been observed in practice.
  • Fixed transaction isolation property in case of ITransaction::remove(...,false) calls.
  • Fixed unit test setup to support CMAKE_TEST_LAUNCHER.

• MDL Compiler and Backends

  • Fixed mangling/demangling of functions with arrays. The mangling name of arrays was
    created wrongly and demangling was missing; however, the mangler still created unique
    names for MDL functions, so this bug was not discovered and does not have any bad
    effect other than poor readability, as the generated names could not be demangled.
  • Fixed mangling/demangling of function instances (i.e., template instantiations). The
    mangling name of instantiated functions with instantiated arrays was computed wrongly
    and demangling was missing; however, the mangler still created unique names for MDL
    functions, so this bug was not discovered and does not have any bad effect other than
    poor readability, as the generated names could not be demangled.
  • Fixed GLSL backend creating a double const modifier for type names, which was
    flagged as a syntax error by the GLSL compiler.
  • Fixed a crash in the material instance opacity analyzer due to a missing break in
    a case statement.

• MDL SDK examples

  • Fixed a bug in the recently added support for subsurface sampling in example df_vulkan.
  • Fixed recognition of MaterialX files, which also triggered on MDL modules containing
    the substring .mtlx.
  • Example DXR:
    • Fixed intermittent texture cache race during parallel material loading.

• MDL Core examples

  • Example df_native:
    • Fixed texture gamma mode being ignored.