Launched at SIGGRAPH 2014, Arnold for Houdini (or HtoA) provides a tight bridge to the Arnold renderer from within the standard Houdini interface, in a way that is familiar to both Houdini users and Arnold users in Maya or Softimage. It also enables smooth lighting workflows between Houdini and other DCC applications, since setups can be exported and shared.

Features
All Arnold cameras (perspective, orthographic, spherical, fisheye) with depth of field and advanced shutter controls.
All Arnold lights (point, distant, spot, quad, disk, cylinder, skydome, mesh) with light filters and accurate viewport representation.
Custom Arnold shading network context with a comprehensive list of 106 shaders and utilities.
Atmospheric and background effects.
Volume rendering with support for OpenVDB and particles.
Polymeshes, curves, points with support for displacement and bump mapping and subdivision.
Procedurals, with sample Alembic and mandelbulb implementations.
Accurate motion blur (transform, deform, velocity, acceleration), overridable per object.
Geometry attributes translation as user data.
Optional Arnold properties for objects and cameras.
Render to AOVs, in single or separate files.
Support all Houdini rendering contexts (render region, mplay, render viewer, render COP, batch), with support for AOVs and clickable buckets.
Interactive rendering (IPR) allows parameter changes to be rapidly previewed without interrupting your work.
Instancing.
Multi-camera renders.
DeepEXR support.