This is a feature release, with support for polysoup primitives and improved volume multiple scattering.
Compatibility
This release uses Arnold 4.2.8.0 and OpenVDB 3.0.0.
Binaries available for the following Houdini, Houdini FX or Houdini Education production builds:
14.0.395
14.0.361
14.0.335
and for the following platforms:
Linux x86_64 (gcc4.4)
Windows 7 x64 (vc11)
Mac OS X 10.8+
Please note that Houdini Apprentice and Houdini Indie do not support third party renderers and thus cannot run HtoA.
Enhancements
Core enhancements, see the full Arnold 4.2.8.0 release notes for more details.
Improved volume multiple scattering: The importance sampling for volume indirect rays has been modified, increasing render time a little, but significantly reducing noise fireflies in various cases.
Faster .ass writing: Writing large .ass files is now 40% faster without compression and 8% faster with .gz compression. Limits on the length of string parameter values have been removed from the .ass parser as well.
Object space adaptive tessellation: Polymeshes have a new subdiv_adaptive_space attribute for subdivision surfaces. subdiv_adaptive_space raster corresponds to the previous behaviour and subdiv_adaptive_space object corresponds to adaptive subdivision in object space. This is useful for instances or when adaptive tessellation is desirable regardless of a specific camera. In line with this new option, subdiv_pixel_error is now called subdiv_adaptive_error. Also, Arnold will warn when raster-space tessellation is used on more than one visible instance.
Wireframe support for non-linear cameras: Wireframe renders now preserve line width when using non-linear cameras such as the built-in spherical and fisheye cameras.
Image texture offsets: The image node now has soffset and toffset parameters for offsetting the textures. This offset takes place before scaling, flipping, or swapping of the S and T coordinates.
Opacity blending supported for FLOAT AOVs: Opacity blending is now supported for AOVs of type FLOAT, in addition to the previously supported RGB and RGBA.
Integrator details in logs: The log files now include more information about the number of samples, GI depths and transparency. Per light volume sampling information was also added. Also, there have been a number of small cleanups and fixes in log files, like removing the legacy, detailed SSS stats, which should result in cleaner, shorter, more reliable and informative logs.
Updated to RLM 11.3BL1: We have upgraded the license server and the external library controlling the licensing subsystem from version 11.2BL2 to 11.3BL1, a more stable release fixing various crashes, bugs, hangs and memory leaks.
HtoA enhancements
Added support for polysoup primitives. Using polysoups gives a 1.75x translation speedup against the equivalent plain polygons geometry
AtString optimizations in shaders resulting in up to 7% faster renders when querying user data
Automatic creation of the Arnold properties tab on Geometry, Instance and Camera OBJ. This behavior can be disabled by setting the HTOA_AUTOPROP environment variable to 0
Allow grouping of several AOVs in a separate file when they share the same filename
You can now control the temporary .ass file location and timeout with the HTOA_TMP and HTOA_TMP_TIMEOUT environment variables
Clarification for the Arnold Volume OBJ and Volume Collector shader UI
Hush log output for progressive passes
Added opacity parameters on the Skin shader
Fixes
Fixed Arnold Procedural and Arnold Volume cannot be selected in the light linker
Fixed shader arrays declared as AI_TYPE_POINTER instead of AI_TYPE_NODE
Fixed regression that disabled motion blur on volumes and procedurals except with Start on Frame
Fixed handling of field of view, parameter translation and IPR updates for custom cameras
Fixed corner cases related to invalid or empty geometry for simple or point instancing
Fixed material not applied to volume instances
Fixed IPR updates for lights with applied light filters
Incompatible changes
Deep EXR files use (AR, AG, AB) as opacity channels: Deep OpenEXR files were using the old (RA, GA, BA) names for three-channel opacity. We have switched to (AR, AG, AB) to follow the EXR standard. Note that Nuke (as of 9v6) does not yet correctly display these deep files anyway.
Single channel texture lookups: In the Image shader, instead of returning it in the R channel only, the single channel is now returned in the R,G,B channels as monochrome RGB
Too-small procedural bounds now an error: Bounds specified for procedurals that end up being too small (and therefore potentially clipping away parts of the object) have been upgraded from a warning to an error. With options.abort_on_error turned on, this will halt the render, which is safer and more reliable than random, non-deterministic, hard to debug clipping of these objects.
The ar_subdiv_pixel_error Arnold property has been renamed ar_subdiv_adaptive_error
Removed linkability of the enumerate parameters of State* and Length shaders