Compared to other recent Arnold releases, Arnold 7.2.4 is a less significant update, described in the documentation as a release with minor changes. The toon shader now better detects inner edges, resulting in previously missed contours displaying correctly, as shown in the image below.
Performance improvements in Arnold 7.2.4 include higher quality mesh light sampling, with rendering times in scenes with multiple light sources reduced by "up to 5%." Interactive rendering has also been enhanced, although specific performance gains aren't mentioned in the release notes. Workflow changes include support for color space aliases in the OCIO color manager and the removal of naming restrictions on nodes in custom MaterialX node definitions.
All Arnold integration plugins have been updated to support the new features:
3ds Max: MAXtoA 5.6.5
Cinema 4D: C4DtoA 4.6.6
Houdini: HtoA 6.2.4.0
Katana: KtoA 4.2.4.0
Maya: MtoA 5.3.4
Arnold 7.2.4 is available for Windows 10 and higher, RHEL/CentOS 7 and higher Linux, and macOS 10.13 and higher. Integration plugins are available for 3ds Max, Cinema 4D, Houdini, Katana, and Maya. GPU rendering is supported only on Windows and Linux and requires a compatible Nvidia GPU. The software is only available through a subscription model, with a single-user subscription costing $50 per month or $400 per year.