Materialx

Added
- Added support for the [fract node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2169), with implementations in GLSL, OSL, and MDL.
- Added a bitangent input to the [bump node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2196), aligning its feature set with the normalmap node.
- Added support for [OSL 1.14](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2204) in shader generation, leveraging the latest closures when available.
- Added support for [MDL 1.10](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2214) in shader generation, leveraging the latest closures when available.
- Added initial support for [data library builds](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2226), allowing future releases to generate derived artifacts from the MaterialX data libraries.
- Added an [ElementVec type alias](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2231) in MaterialX C++, allowing certain patterns to be expressed more clearly and concisely.

Changed
- Improved the compatibility of MaterialX shader generation with [Hydra Storm](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2211).
- Refactored the [type system](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2176) in shader generation, improving the thread-safety and robustness of the generation process.
- Improved the implementations of the [BSDF operator nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2191), preferring data definitions over explicit C++ code.
- Improved the implementations of the [time node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2192), using a graph definition in hardware shading languages.
- Optimized [GitHub CI](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2253) to reduce build times for contributors.
- Raised the minimum CMake version to [CMake 3.26](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2235).

Fixed
- Fixed two edge cases in the [version](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2248) [upgrade](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2251) logic for normalmap nodes, addressing the usage of MaterialX versioning in OpenUSD.
- Fixed [tangent frame orthogonalization](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2245) for the normalmap node in OSL shader generation.
- Added validation of [tree depth](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2232) and [XInclude depth](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2233) in XML parsing, addressing cases where unusually complex documents could trigger a stack overflow.
- Adding two missing [null](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2228) [checks](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2229) in the getShaderNodes helper function.
- Integrated fixes to [OSL type classes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2200) from recent work in the OSL project.
- Improved the handling of [invalid materials](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2230) in the MaterialX Viewer, addressing cases where missing lights could trigger a crash.

Added
- Added support for the [Chiang Hair BSDF](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1968), with initial implementations in hardware shading languages and MDL.
- Added support for the [Disney Principled](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2004) shading model, implemented as a language-independent graph.
- Added support for [generic color ramps](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1884), using a graph-based ramp node with ten control points.
- Added support for [Worley noise with solid cells](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2119), opening up new artistic options for metal flake shaders.
- Added support for [data library referencing](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2054), enabling improved performance in shader generation.
- Added support for [custom structure types](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1831) in MaterialX.
- Added support for [functional equivalence](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2003) tests between MaterialX elements.
- Added support for [geompropvalueuniform nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2092), improving functional parity between MaterialX and USD.
- Added support for [transmission effects](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2027) in the translation graph from Standard Surface to glTF PBR.
- Added support for [coated emission](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2087) in the translation graph from Standard Surface to UsdPreviewSurface.
- Added support for [Apple framework builds](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2020).
- Added support for [MDL 1.9](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2102) in shader generation.
- Added support for [viewdirection space](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2036) in hardware shading languages.
- Added support for [image downsampling](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2159) in MaterialXRender.
- Added support for [image difference statistics](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2160) in render tests.
- Added a [combined version define](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2031) to MaterialX C++.
- Added a [release signing workflow](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2009) to GitHub Actions.
- Added documentation for [keyboard shortcuts](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2026) in the MaterialX Viewer.

Changed
- Improved the performance of [graph traversal](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2023) by skipping edges that have already been visited.
- Reduced duplication between the [MSL and GLSL implementations](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2068) of nodes.
- Updated the [UsdPreviewSurface shading model](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2084) to v2.6, maintaining the visual interpretation of existing assets.
- Raised the [minimum OSL version](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2144) to v1.12.6 in OSL shader generation.

Fixed
- Fixed [unintentional camera orbiting](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2032) in the render view of the MaterialX Graph Editor.
- Fixed [banding artifacts](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1977) in the MaterialX Viewer on MacOS.
- Fixed the handling of [missing scenes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2124) in the MaterialX Web Viewer.
- Fixed an edge case for [node pasting](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2145) in the MaterialX Graph Editor.
- Fixed the implementation of [texture filtering](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2158) in OSL shader generation.
- Fixed the implementation of the [heighttonormal node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2165) in OSL shader generation.
- Fixed a call to the [anisotropic_vdf closure](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2016) in OSL shader generation.

Removed
- Removed support for the [legacy OSL closures](https://github.com/AcademySoftwareFoundation/MaterialX/pull/2121), focusing exclusively on the MaterialX-synchronized closures in OSL 1.12 and beyond.

Added
- Added initial shader translation graphs between [Standard Surface](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1934) and [OpenPBR Surface](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1949).
- Added initial support for [code generation hints](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1954).

Changed
- Raised the minimum CMake version to [CMake 3.24](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1929).
- Moved feature proposals from the main specification to a new [MaterialX Proposals](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1953) document.
- Updated the open definitions of the [MaterialX Lama nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1955) to improve alignment with RenderMan.

Fixed
- Fixed errors in the [installation steps](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1923) for CMake builds.
- Fixed the computation of [Fresnel transmission](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1962) in GLSL.
- Fixed an implementation of the [combine2 node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1975) in MDL.
- Fixed transposed matrices in color transforms for the [displayp3 space](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1960).
- Fixed edge cases in the version upgrade process for [swizzle](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1945) [nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1957).
- Fixed a crash in the Graph Editor when [renaming a node graph](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1930).
- Fixed the exporting of [PugiXML symbols](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1944) in MaterialXFormat.

Removed
- Removed an extra installation of the [resources folder](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1927) in MaterialXGenShader.

Added
- Added support for the [OpenPBR Surface](https://academysoftwarefoundation.github.io/OpenPBR/) shading model, including the [MaterialX definition](https://github.com/AcademySoftwareFoundation/MaterialX/blob/main/libraries/bxdf/open_pbr_surface.mtlx) and [example materials](https://github.com/AcademySoftwareFoundation/MaterialX/tree/main/resources/Materials/Examples/OpenPbr) for OpenPBR Surface v1.1.
- Added support for [Hoffman-Schlick Fresnel](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1727), [Zeltner sheen](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1880), and [energy-compensated Oren-Nayar diffuse](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1822), with initial implementations in hardware shading languages.
- Added support for the [LamaGeneralizedSchlick and LamaIridescence](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1897) nodes, with definitions provided as MaterialX graphs.
- Added support for integer-type [add, subtract](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1777), and [conditional](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1786) nodes.
- Added support for matrix-type [switch](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1779) and [conditional](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1780) nodes.
- Added support for additional [convert node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1905) input and output types.
- Added support for [monolithic builds](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1725) of MaterialX.
- Added support for the [full set of shader generators](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1771) in JavaScript.
- Added support for [frame timing](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1739) in the MaterialX Viewer.
- Added a [uiScale option](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1586) for adjusting DPI in the Graph Editor.
- Added an example script to [generate a MaterialX document](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1746) from a folder of textures.
- Added unit tests for [core utilities](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1768) and [ESSL shader generation](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1781).
- Added support for [Python 3.12](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1802) in Python wheel generation.
- Added [GCC 14](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1913) and [Clang 18](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1820) builds to GitHub Actions CI.

Changed
- Raised the minimum C++ version for MaterialX builds to [C++17](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1712).
- Updated the [PyBind11 library](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1839) to version 2.12.0, enabling support for recent compilers and CMake versions.
- Improved the expression of [thin-film layering](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1413) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Improved the generality of the [normalmap node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1911) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Extended the [switch node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1660) to ten inputs in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Renamed the inputs of the [atan2 node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1659) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Changed the type of [subsurface_bsdf radius](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1834) from vector3 to color3 in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Renamed the [normalmap nodedef](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1677) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Improved the support for [double-sided materials](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1866) in MaterialX 1.39.
- Optimized [Fresnel](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1732) [computations](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1733) in [GLSL](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1736), improving the performance of physically based shading in real-time renders.
- Applied [lossless optimization](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1738) to PNG and JPG textures in the MaterialX repository.

Fixed
- Fixed default values for the [creatematrix node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1788).
- Fixed an issue with [keyboard input focus](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1596) in the Graph Editor.

Removed
- Removed the [swizzle node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1793) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Removed the [channels attribute](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1804) in MaterialX 1.39, with automatic upgrade logic for legacy documents.
- Removed the unimplemented [arrayappend node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1707) in MaterialX 1.39.

Added
- Added support for [environment light intensity](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1737) in generated GLSL shaders.

Changed
- Removed an [extra suffix](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1744) from element names in texture baking.

Fixed
- Moved environment prefilter functions to their [referencing GLSL files](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1748), addressing shader compilation errors in USD.
- Enabled color and unit transforms on [root nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1757) in shader generation, addressing missing color transforms in USD.
- Updated [document caches](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1753) to store elements in declaration order, addressing compiler-dependent behavior in nodedef lookups.
- Switched to [framework linkage](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1752) for OpenGL libraries on MacOS, addressing build issues in downstream projects.
- Switched to [legacy OpenGL libraries](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1766) for Python wheels on Linux, addressing missing OpenGL functionality in Python wheels.
- Added a [missing vertex data prefix](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1762) in Vulkan GLSL shader generation.

Added
- Added an initial NPR (non-photorealistic rendering) data library to MaterialX, supporting the [View Direction](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1631), [Facing Ratio](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1671), and [Gooch Shading](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1674) nodes.
- Added new nodes to the standard data library, including [Reflect](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1690), [Refract](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1698), [Safe Power](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1689), [Create Matrix](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1553), and [Round](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1678).
- Added support for the generation of [pre-filtered environment maps](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1420) in MaterialX GLSL and MSL.
- Added support for [geometry drag & drop](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1663), [frame capture](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1636), [UI ranges](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1623) and [enumerated values](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1632) in the MaterialX Web Viewer.
- Added [floating popups](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1565) for hovered pins in the MaterialX Graph Editor.
- Added [UI ranges](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1646) to the 'useSpecularWorkflow' and 'normal' inputs of the UsdPreviewSurface shading model.
- Added [versioning rules](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1664) for the MaterialX API and data libraries to the developer guide.
- Added initial C++ [fuzz tests](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1605) and [coverage tests](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1548) to GitHub Actions CI.
- Added [GCC 13, Clang 15](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1602), and [Python 3.12](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1588) builds to GitHub Actions CI.

Changed
- Enabled the [new OSL closures](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1702) by default in shader generation, with the MATERIALX_OSL_LEGACY_CLOSURES flag used to request legacy closures.
- Updated the MaterialX Web Viewer to [three.js r152](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1615).
- Switched to a more efficient representation of [HDR images](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1616) in the MaterialX Web Viewer.
- Improved the logic for [connecting pins](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1569) in the MaterialX Graph Editor.
- Improved the handling of [filename inputs](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1547) in OSL shader generation.
- Reduced the size of the MaterialX data libraries, improving the use of [graph definitions](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1653) and merging [duplicate implementations](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1642).
- Raised the minimum CMake version to [CMake 3.16](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1607).
- Updated the C++ unit test library to [Catch 2.13.10](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1566).

Fixed
- Fixed the attenuation of [coated emission](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1534) in the Standard Surface shading model.
- Fixed the implementation of the [overlay node](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1539) in shader generation.
- Fixed an edge case for [type pointer comparisons](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1665) in shader generation.
- Fixed an edge case for [transform nodes](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1560) in GLSL and MSL shader generation.
- Fixed the implementation of [mx_hsvtorgb](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1584) in MDL shader generation.
- Fixed [orphaned links](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1667) when deleting nodes in the MaterialX Graph Editor.
- Fixed [scroll wheel interactions](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1578) across windows of the MaterialX Graph Editor.
- Fixed the generation of unused [imgui.ini files](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1570) in the MaterialX Graph Editor.
- Fixed a dependency on [module import order](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1595) in MaterialX Python.
- Fixed an [off-by-one index check](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1582) in Element::setChildIndex.
- Fixed a [missing null check](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1601) in Graph::propertyEditor.
- Fixed cases where [absolute paths](https://github.com/AcademySoftwareFoundation/MaterialX/pull/1603) were stored in MaterialXConfig.cmake.