What's New in Arnold - Arnold User Guide

Arnold 7.4.x

Volume Rendering

Arnold 7.4.5.0 Volume mip maps The Arnold volume node now accepts OpenVDB files with mip-mapped grids, which gives substantial speedups in volumes with a lot of scattering (for example, clouds). Faster GPU volume rendering

Line shader

Arnold 7.4.5.0 The new line shader renders lines in various styles to create geometric patterns or brush-stroke-like textures when combined with noise and textures. You can generate complex hierarchical patterns by connecting line shaders together. We recommend using the line shader with uv_transform. (ARNOLD-14976)

Point cloud queries

Arnold 7.4.5.0 nearest_points shaderThe new nearest_points shader samples point clouds from OpenVDB points files, or alternatively, the vertices from points, curves, and polymesh nodes. The shader can output the number of points found, average distance, or an average of a custom, user-data attribute from the points. (ARNOLD-15550) OSL support for point cloud search and getArnold now supports the built-in OSL pointcloud_search and pointcloud_get functions. To specify a points, curves, or polymesh node, use the node name for the point cloud name. To specify an OpenVDB file, use the format filename:grid for the point cloud name. Currently these functions are supported for CPU rendering only in this release. (ARNOLD-15550)

Bloom color dispersion

Arnold 7.4.5.0 The imager_lens_effect node has a new aperture_dispersion parameter, which controls the amount of color dispersion when in bloom_mode aperture. Increasing the dispersion value spreads the different colors further apart, decreasing it brings the colors closer together. (ARNOLD-16912)

Scattering mode for standard hair

Arnold 7.4.4.0 A scattering option scattering_mode has been added to the standard hair shader. Use the approximate mode to get the previous behavior. The accurate mode can be noisier, and so takes about 10–30% longer to render, but delivers more realistic results, especially in close-ups, by simulating each hair as a cylinder instead of flat surface. The adaptive mode uses the accurate mode for close-up hairs and the approximate for far-away hairs, automatically balancing quality and performance.

Improved bloom lens effect

Arnold 7.4.4.0 The lens effects imager has improved bloom modes that can run in a fraction of a second and produce more interesting bloom effects. The new aperture bloom mode procedurally mimics the bloom defined by a physical camera and you can control the size with bloom_strength, and the shape and number of spikes with aperture_blades and aperture_curvature. The other new mode, shape_file allows you to load a bloom kernel from disk.

Faster rendering with Global Light Sampling

Arnold 7.4.3.0 Scenes using Global Light Sampling, render up to 2.5x faster in our tests. The numbers below are for same-noise renders. (ARNOLD-13091)

Improved Global Light Sampling (GLS) on glossy material in GPU renders

Arnold 7.4.3.0 GPU renders (like CPU renders since Arnold 7.3.7.0) now take material glossiness into account when sampling, which greatly enhances the quality especially when many small lights are present. In the robot scene below, we get a ~3x speedup with adaptive rendering. (ARNOLD-15833)

Faster volume rendering on GPU

Arnold 7.4.3.0 Scenes with volumes (procedural or OpenVDB) render up to 3.3x faster in our tests. Scenes with OpenPBR transmission or scattering materials render up to 1.2x faster. (ARNOLD-11077, ARNOLD-16304)

Inference Imager

Arnold 7.4.3.0 This imager is capable of performing inference on image-to-image machine learning models using the ONNX framework.

Arnold Performance Improvements

Arnold 7.4.1.0 Significant updates to Arnold greatly improve rendering performance for scenes with complex hierarchies and point instancers. Time to first pixel, interactivity in IPR, and scene processing time for batch renders are also faster.

GPU Toon Shading

Arnold 7.4.1.0 Arnold GPU now includes initial support for the Toon shader and the contour filter. The Toon shader is currently limited to rendering direct lighting only (no reflections, refractions, or indirect lighting). (ARNOLD-15656, ARNOLD-15988)

Render Report

Arnold 7.4.1.0 An HTML-based, interactive viewer for the Arnold render statistics. You can quickly visualize and inspect detailed render stats such as frame render time, memory usage, render time by category or by node, and texture usage. If you're using kick, add the -report flag. Arnold plugins like MtoA and HtoA include Render Report options in the Diagnostic render settings. (ARNOLD-14140)

MaterialX

Arnold 7.4.0.0 MaterialX has been upgraded to v1.38.10-OpenPBR, this new version brings support for the OpenPBR MaterialX node, improved Lama support and new nodes such as the NPR nodes. See v1.38.10, v1.38.9 release notes for details. (ARNOLD-15659)

OpenVDB points support in aiVolume node

MtoA 5.5.1 You can now load VDB files that contain points data and render them as Arnold points primitives (MTOA-2234)

Save snapshots with render logs in the Arnold Render View

MtoA 5.5.1 When saving snapshots you can now save the current render log and view them in the Arnold Render Logs window (ARNOLD-12266)

Arnold 7.3.7.0

Improved, More Realistic Shadows for Glass Objects

Arnold 7.3.7.0 Transparent objects like clear glass now cast shadows. The look of the shadow is controlled by the new transmission_shadow_density parameter on the openpbr_surface and the standard_surface shaders. (ARNOLD-6881, ARNOLD-15863, ARNOLD-15828)

Improved Global Light Sampling (GLS) for Glossy Materials

Arnold 7.3.7.0 Global Light Sampling (GLS) now takes material glossiness into account when sampling. That greatly enhances the quality especially when many small lights are present and in adaptive setting it brings good speedups in such scenes. (ARNOLD-15489)

OpenVDB Points Rendering

Arnold 7.3.7.0 The points node has new parameters for loading points from a points grid in an OpenVDB file. At a minimum, you must set the file_name and file_grid parameters to load an OpenVDB file. Arnold tries to guess the point attributes for position, radius and velocity, but these attributes from the grid can be specified directly if needed. All other point attributes that reasonably map to Arnold data types are available to shaders as user data. Note that not all Arnold plugins expose the points node. (ARNOLD-15663)

More Arnold Enhancements

More Normal Types for triplanar

Arnold 7.3.6.0 The triplanar shader has a new parameter normal_type which can be used to select the type of normal to use for selecting the dominant axis for texturing. The options are shading, which is the previous behavior and uses the smooth shading normal (this normal includes bump), smooth_and_displaced is like the shading normal but without the bump, and finally smooth_before_displacing gives the smooth normal before displacement and bump. Note that smooth_before_displacing requires that autobump be enabled. (ARNOLD-15523)

Cryptomatte support on GPU

Arnold 7.3.5.0 Arnold now has an internal implementation of Cryptomatte that supports GPUs. On both CPU and GPU, Cryptomatte now also uses much less memory for samples, making it easier to use higher AA settings, progressive rendering, and adaptive rendering (when properly used with FIS). In a simple scene rendered at 640x480 resolution with three cryptomattes we see the following improvements in peak memory. (ARNOLD-11042)

Arnold cameras in Hydra

Arnold 7.3.5.0 Arnold Cameras in Hydra: Arnold cameras (vr, cylindrical, spherical, uv, fisheye) are now supported in Hydra. You create the Arnold cameras as USD built-in cameras, with a string primvar arnold:camera that specifies the Arnold camera type. (usd#1738 usd#2082) Arnold camera types now supported in the Houdini Solaris Camera LOP (HTOA-1749)

Faster OpenVDB volume intersection

Arnold 7.3.5.0 Intersecting OpenVDB volumes are optimized for many-cores. Scenes where volume::intersection is a sizable component of render time can see large speedups. One scene where it accounted for 73% of render time on a 128-core machine saw the volume::intersection time drop to 16% of total time, for an overall 3x speedup in render time. (ARNOLD-15448)

GPU: Support element linking of array parameters in ramp shaders

Arnold 7.3.5.0 Arnold GPU supports the linking of individual ramp parameter components for the position, value, color, and interpolation parameters. (ARNOLD-7120)

MaterialX OSL closure support

Arnold 7.3.5.0 The OSL closures defined by MaterialX (v1.38) for definition of layered physical materials have been ported to Arnold. As one key application, the OpenPBR surface model has been implemented in Arnold via these closures as an OSL shader (as well as a native C++ shader).

Faster uv_camera baking

Arnold 7.3.5.0 The uv_camera.grid_size default is now 0 instead of 16, where 0 specifies that the grid_size is automatically chosen. Using the new default, baking a sphere with 800k triangles is now 6.5x faster than the previous default. (ARNOLD-15441)

Cryptomatte support on GPU

MAXtoA 5.7.6.0 Support Isolate Selected for materials and maps: Isolate Selected in the Arnold RenderView now works for materials and maps as well as objects and lights. To use this, make sure no objects or lights are selected, and then select one (or more) materials or maps in SME. The selected materials and maps are rendered in the Arnold RenderView, making it easier to debug complicated shader trees. (MAXTOA-1852)

OpenPBR Surface and Standard Hair presets

C4DtoA 4.7.8 OpenPBR Surface and Standard Hair shader presets are now shipped with C4DtoA. You can load them from the Presets tab or from the Asset Browser. (C4DTOA-3242) (C4DTOA-3301)

OpenPBR Surface

Arnold 7.3.3.0 A new openpbr_surface shader implements the OpenPBR specification. OpenPBR Surface is an evolution of Standard Surface, developed in collaboration with Adobe and the Academy Software Foundation. It introduces many improvements, in particular a better sheen/fuzz model and improved metal reflectivity parameterization. (ARNOLD-13385)

Scattering diffusion in volumes

Arnold 7.3.3.0 Two new parameters in standard_volume improve how light is scattered in volumes. scatter_diffusion accelerates scattering volumes. scatter_diffusion_roughness improves scattering specifically in highly isotropic volumes. gain and bias curves can further tweak the effect of both parameters (ARNOLD-14482)

Stochastic volume interpolation

Arnold 7.3.3.0 The tricubic interpolation mode of AiVolumeSampleXXX() calls, such as those used by the standard_volume shader, now uses a stochastic method of interpolation that greatly reduces the amount of voxel data read in each sample call. This can speed up rendering by as much as 20% in assets such as the WDAS cloud data set. Note that this technique does not always produce a perfectly matching image as a result, and can be toggled via the stochastic_volume_interpolation render option (default is on). (ARNOLD-3856)

Intel Open Image Denoise (OIDN)

Arnold 7.3.3.0 OIDN support for Apple Metal and AMD GPU The Intel OIDN denoiser now supports all Apple Metal hardware (M1 and newer) and AMD GPUs using RDNA2 (Navi 21 only) and RDNA3 (Navi 3x) architectures. This allows for significantly faster denoising. (ARNOLD-14855, ARNOLD-14856) Update to Intel Open Image Denoise (OIDN) 2.3.0 The updated Intel Denoiser improves denoising quality and can produce sharper results with less artifacts on scenes with specular reflections and transmission. For more information about changes in this version, see the OIDN release notes (ARNOLD-15059).

USD Enhancements

Arnold 7.3.3.0 Skinning on USD curves and points - Binding skeleton on BasisCurves and points will now work with the procedural. usd#1814 User data on lights - Support primvars as user data on lights. usd#1939 Renders abort on license fail - The render delegate used by husk aborts a render if a license isn't found and the environment variable ARNOLD_FORCE_ARBORT_ON_LICENSE_FAIL is set to 1. usd#1950 Reduced memory usage when using husk - When rendering one frame, the render delegate switches to the batch render mode, which consumes less memory than the interactive mode. usd#1918 Improved quad and mesh light exports - Mesh lights are now exported as a Mesh with light attributes instead of a GeometryLight. usd#1955

GPU Improvements and Optimizations

Arnold 7.3.3.0 GPU improved time to first pixel in scenes with many nodes educed time to first pixel with Arnold GPU and scenes with many nodes. For example, we have seen a 18% improvement in time to first pixel on a simple scene with 1,000,000 instances. (ARNOLD-13652) GPU Many-lights support for light linking: Arnold GPU now uses Global Light Sampling for group of lights linked to a shape. This can improve rendering performance for scenes with light linking. For example, the ALab scene now renders twice as fast when you use Global Light Sampling. (ARNOLD-15050) Motion vector AOV on GPU: The motionvector AOV is now supported when rendering on GPU. (ARNOLD-11046)

Ramp shader 3d modes and offsets

Arnold 7.3.3.0 3D ramp modes: Ramp shaders have three new modes: 3d_linear, 3d_spherical, and 3d_cylindrical. These modes calculate the ramp input from the distance between the shading point and a user-defined reference point or line. (ARNOLD-15051, ARNOLD-15196) 3d_linear 3d_spherical 3d_cylindrical Ramp offset: Ramp shaders can now offset the input value, which allows you to add noise to the ramp. (ARNOLD-15052, ARNOLD-15197) worley noise (3d_spherical) cell_noise (u) alligator noise (v)

Tonemap Imager Creates Heatmaps

Arnold 7.3.3.0 The tonemap imager now has a heatmap mode that creates a spectrum based on a looked-up AOV quantity. The color ranges from blue (at minimum) to red (at maximum) (ARNOLD-15123).

Improved AOV memory usage in non-progressive renders

Arnold 7.3.3.0 Non-progressive, adaptive renders with the box filter now use less memory. Memory usage is also reduced in non-adaptive renders when using the following filters gaussian_filter, triangle_filter, sinc_filter, catrom_filter, mitnet_filter, blackman_harris_filter. For example, in a 1080p render using adaptive with AA_samples_max 50 and 6 AOVs, the memory used by AOVs was reduced from 14GB to 730MB (-96%). Note also that AOV memory usage now remains constant as AA_samples_max increases, unlike previous releases where the memory would increase quadratically. (ARNOLD-10160)

Improved efficiency of the Alembic procedural

Arnold 7.3.3.0 The Alembic procedural now reads data in parallel, which optimizes initialization times of heavy Alembic files with many objects. We observed startup times going from 15 minutes to 4 seconds on a large production scene. (ARNOLD-14796)

API Changes

Arnold 7.3.3.0 New shader, threading, and critical section APIs.

Motion vector AOV on GPU

Arnold 7.3.3.0 The motionvector AOV is now supported when rendering on GPU. (ARNOLD-11046)

Toon hue saturation tone-mapping

7.3.2.0 You can now drive the hue and saturation of tonemapping in the toon shader through a set of four new parameters that complement the existing value-based tonemapping parameters.

Better volume denoising

7.3.2 Denoising volumes now produces better results. The changes in how volume albedo is computed help the denoiser to keep more details. Ringing artifacts when objects are viewed against the background are also reduced, and a new N_denoise AOV fixes some denoising artifacts visible in low-AA renders. (ARNOLD-14936, ARNOLD-13071)

Geometry Baking

7.3.2 Thanks to a new API for baking geometry, all Arnold plugins can now bake subdivided and displaced polygon meshes to disk.

Many-lights support for light linking

7.3.2 Global light sampling is now applied per group of lights linked to a shape. That can improve rendering performance for scenes with light linking. The ALab scene now renders twice as fast when you use Global Light Sampling. (ARNOLD-14985)

Improved Standard Hair on GPU

7.3.2.0 The GPU renderer now supports the extra_depth parameter. This enables accurate rendering of blond or bright-colored hair without raising GI_specular_depth.

Improved volume albedo AOV

7.3.2 Volume albedo values are now more physically-based. This improves volume denoising and any LPE AOV using volume albedo is now much more useful for compositing. For backwards compatibility, you can set the new global option legacy_volume_albedo to true. (ARNOLD-13071)

Improved OSL interoperability

7.3.2 The color4, color2, vector4, vector2, and matrix33 are now supported as output types of OSL shaders when connected to Arnold shaders. Additionaly, Arnold shaders that output RGBA or Vector2 types can now be directly connected to OSL shader color4 and vector2 input parameters. Those features make it easier to mix Arnold and MaterialX standard library shader nodes. (ARNOLD-13989, ARNOLD-14692)

Imager plugin API

7.3.1 A public API is now available for imagers. This adds support for custom and third-party imagers in Arnold. (ARNOLD-10322)

Automatic Denoising

Arnold 7.3.1 For new scenes, Arnold plugins such as MtoA and MAXtoA now automatically denoise renders with the Intel® Open Image Denoiser (OIDN) imager. New scenes automatically include the Intel Denoiser imager; existing scenes are not changed. You can disable the automatic denoising for new scenes in the plugin Arnold Render Settings.

Progressive dithered sampling

7.3 Arnold now supports dithered samples in progressive and adaptive rendering. Dithering brings nicer noise distributions at low AA sample counts.

GPU Renderer Overhaul

7.2.5 A large part of the GPU renderer was rewritten using NVIDIA OptiX 8. This allowed numerous improvements such as much faster startup times and better scaling on multiple GPUs.

Global light sampling in volumes

7.2.5 Global light sampling is now supported in volumes. The render time speedup when using global light sampling in volumes depends on the number of lights, but even scenes with only a few lights are faster to render.

Distance shader in reflections

7.2.5 The distance shader now properly handles secondary paths such as reflections.

Overlay imager

7.2.5 A new imager that allows you to decorate or tag your renders by printing text over the rendered images.

Improved thick curves intersector

7.2.5 Curves in thick mode are on average 10% faster (in some cases, more than 100% faster) and they look better in closeups.

Toon light-group AOVs

7.2.5 The toon shader now outputs AOVs for direct lighting from lights that have a label in their aov parameter.

OptiX denoiser runs on progressive negative AA passes

7.3.1 The OptiX denoiser imager now denoises the low-resolution progressive passes (renders with AA < 0). This should result in higher quality feedback in IPR. (ARNOLD-11487)

Update Intel Open Image Denoise (OIDN) to version 2.2.2

7.3.1 The updated denoiser has 10% better performance on CPU, includes some critical bug fixes, and handles high-frequency details better. (ARNOLD-14772)

MaterialX node definitions

7.3.1 The MaterialX node definitions for Arnold shaders now use the standard surfaceshader and volumeshader types, which make them easier to use in DCCs and mix with standard library shaders. The UI for Arnold MaterialX shaders is also improved with the addition of parameter groups and node categories. (ARNOLD-14717, ARNOLD-14736, ARNOLD-14716)

OCIO environment variable

7.3.1 The OCIO environment variable now takes priority over the builtin OCIO configuration file. The OCIO environment variable is now taken into account by maketx. (ARNOLD-9012)

Curves support in procedural viewport API

7.3.1 Procedurals can now return curves nodes in AI_PROC_POLYGONS viewport mode. (ARNOLD-14756) Currently, only C4DtoA and KtoA support the display of Arnold curves in the viewport.

USD - Light linking on custom procedurals

7.3.1 You can now use light linking on custom procedurals such as Yeti in the render delegate. (usd#1730)

Device selection in the Intel Denoiser

7.3 It is now possible to toggle between Auto/CPU/GPU for OIDN denoiser imager. Arnold now also provides accurate timing information for the denoiser in the log. (ARNOLD-14526) (ARNOLD-14524)

Improved MaterialX support

7.3 Arnold can now render MaterialX node graphs mixing standard library. DCCs loading the Arnold node definitions will benefit from the newly added UI metadata and provide a better user experience. Arnold also now uses MaterialX 1.38.8, this update brings new nodes in the MaterialX standard library, for a full list of changes please see the full release notes (ARNOLD-14286) (ARNOLD-14623, ARNOLD-14513)

Emission and per-light-group AOVs

7.3 Per-light-group indirect AOVs no longer include emission. Emissive surfaces now only appear in the "default" light group output. When using emission in shaders, the sum of the light group AOVs will now add up to the beauty pass.(ARNOLD-9453)

Evaluate autobump in SSS on GPU

7.3 Autobump will now be evaluated in the SSS computation with the GPU renderer when the sss_use_autobump option is enabled, this matches the behavior when rendering on CPU. (ARNOLD-8494).

GPU denoising in Intel Open Image Denoise

7.2.5 The Intel denoiser was upgraded from version 1.4.1 to 2.1.0, which brings real-time denoising through NVIDIA and Intel GPU support.

New network server configuration modes in the License Manager

7.3 You can now use a license file (licpath.lic) or a list of servers to set up redundant and distributed license servers in the Arnold License Manager. (ARNOLD-14586, ARNOLD-14615)

Add license checkout time to render statistics

7.3 The render statistics now include the "license checkout time", which is the time in microseconds spent on license checkout for a specific render. This is useful to users to diagnose long checkout times when rendering in batch. (ARNOLD-13497)

OCIO, Alembic, and ADP upgrades

7.3 Upgrade to OpenColorIO 2.3.1: OpenColorIO library has been upgraded to use version 2.3.1. For the list of changes see the release notes for 2.3 and 2.3.1. (ARNOLD-14026) Updated Alembic to 1.8.5: The Alembic procedural has been upgraded to use version 1.8.5 of the Alembic library. (ARNOLD-14448) Autodesk Analytics Program: A newer version of the Autodesk Analytics Program (ADP) has been integrated into Arnold. This brings stability improvements. (ARNOLD-13805)

Velocity motion blur for points

7.3.1 Points with a velocities attribute now render with motion blur. usd#1868

Export ArnoldOptions as UsdRenderSettings

7.3.1 The Arnold USD exporter covnerts the Arnold options node to UsdRenderSettings, UsdRenderProduct, and UsdRenderVar nodes. usd#1852, usd#1865

Imager node support

7.3.1 USD support for the new Arnold AI_NODE_IMAGER node type. ( usd#1870

Better default for transmission ray depth

7.3.1 Set the default transmission depth to 8, so that the default settings work better with glass, and to match default in other Arnold plugins like HtoA and MtoA. usd#1889

Improved tooltips

7.3.1 The tooltips in DCCs for Arnold nodes in USD is much improved. (usd#1835)

Update to USD 23.11

7.3 The USD version was updated USD from 22.11 to 23.11 in the procedural. The USD Arnold procedural embeds a static version of USD 23.11, see USD 23.11 Changelog for all the changes related to this new version of USD.

Light instances

7.3 You can now instance lights with a Point Instancer. (usd#1705)

Visibility and Mattes on instances

7.3 In the Hydra Render Delegate, the Arnold visibility and matte attributes now work on instances. (usd#1635)

Batch renders now abort on license fail

7.3 Arnold now aborts if there is a license error in a batch render. The option abort_on_license_fail is now true by default, and applies to batch renders only. This means you don't have to check rendered image sequences for watermarks. Interactive renders do not abort, and have a watermark on license fail as usual. The environment variable ARNOLD_FORCE_ABORT_ON_LICENSE_FAIL overrides this default behavior 0 = batch and interactive render with watermarks on license fail 1 = batch and interactive abort on license fail). (ARNOLD-13024)

Improved profiling

7.2.5 Procedural and volume intersection times are now listed separately, instead of being included with the parent BVH. Profiling has also been added in other areas, in particular multithreaded code where helper threads were not being accounted for. This should result in higher quality statistics.

UDSZ files supported as file format

7.2.5 You can render usdz files with kick, load them with the usd procedural, and render them in a Hydra render delegate.

Orthographic cameras in Hydra

7.2.5 Orthographic Cameras are now supported in the Hydra render delegate.

Pixel Aspect Ratio in Hydra

7.2.5 The Arnold Render Delegate now supports the pixelAspectRatio parameter in RenderSetting primitives.

Plugin Enhancements

Support added for camera > backgroundColor

MtoA 5.4.3 The maya camera attrbiute "backgroundColor" is now supported to change the background color of the current render(MTOA-1727)

Standins Viewport Display Color

MtoA 5.4.3 A custom color can be set on aiStandIn nodes to control how they are displayed in the viewport, through the attribute "Object Display/Draw Override/Enable Overrides"

Sphere and Box volume added to aiVolume

MtoA 5.4.3 A new attribute has been added to the aiVolume to set the volume shape to box or sphere, defaults to existing file mode (MTOA-247)

Arnold RenderView Enhancements

MtoA 5.4.3 Including scriptable Save Image options, a new preference for the snapshots folder, and a quick way to deselect snapshots.

Improvements to the Arnold Render View Snapshots

MtoA 5.4.1 The snapshot workflow and interface in the Arnold RenderView has multiple enhancements and behaviours.

Denoising by default with Intel Open Image Denoise (OIDN)

MtoA 5.4.1 The Intel ® Open Image Denoiser imager is now added by default to new scenes (MTOA-1787). More information is available here.

Support for MaterialX shader networks in LookDevX

MtoA 5.4.0 MtoA 5.4.0 adds support for the new LookDevX MaterialX node graph editor. This allows you to assign LookdevX shader networks to Maya geometry and mix MaterialX shader nodes with Arnold shaders. (MTOA-1672, MTOA-1703)

Soloing LookDevX nodes

MtoA 5.4.0 MtoA 5.4.0 adds support for soloing individual shaders in a LookDevX node graph.

OSL Enum support in Attribute Editor

MtoA 5.4.1 Shader parameters of type ENUM on the OSL code node create a combo box with the available options (MTOA-1781)

New presets added to aiRampRgb

MtoA 5.4.1 Over 100 new presets for the aiRampRGB node (MTOA-1630)

Automatic aiStandardVolume shader for new aiVolume nodes

MtoA 5.4.1 When you create an aiVolume node, an aiStandardVolume shader is automatically created and assigned to the aiVolume. (MTOA-1803)

Improved support for USD cameras

MtoA 5.4.1 Cameras from a USD Stage are displayed in the Render View Camera list (MTOA-1597) You can use UFE camera paths when rendering in batch (MTOA-1597) USD Stage cameras are listed in the Render Settings if they are set to the Render purpose (MTOA-1597)

Better editor for the overlay imager

MtoA 5.4.0 The editor for the overlay imager is now more intuitive and previews the choosen font and style. (MTOA-1664)

MAXtoA Toolbar

MAXtoA 5.7.3.0 MAXtoA now ships with a toolbar. Direct access to ARV both for production and IPR, creation of Arnold primitives and modifiers, and access to the most commonly used Arnold features. The toolbar is end-user customizatble by the 3ds Max Customize->Customize User Interface->Toolbar menu item. (MAXTOA-1514)

View Switching improved

MAXtoA 5.7.3.0 When rending interactively in ARV, clicking in different views used to change the view of the render. This is almost never the desired behavior, and this has been removed. If switching to a different view is desired, one can just click the view and click the "IPR" toolbar button to acheive the old behavior. (MAXTOA-1685)

Improved Export

MAXtoA 5.7.3.0 In the past, exporting to .ass file from the File menu's Export option did not allow exporting the scene options, and things associated them. Now, there is a new checkbox for exporting the scene options. (MAXTOA-448)

Automatic Denoising

MAXtoA 5.7.1.0 By default, new scenes automatically have an Intel® Open Image Denoiser (OIDN) imager. A new option in the Render Settings controls whether a denoiser is automatically added when you create new scene. Existing scenes do not get the default denoiser. (MAXTOA-1745)

Dockable Arnold RenderView

MAXtoA 5.7.1.0 The Arnold RenderView window (ARV) is now dockable by default, and follows the behavior of other dockable windows. ARV docking can be turned off in the MAXtoA render settings. (MAXTOA-1722)

Improvements to the Arnold Render View Snapshots

MAXtoA 5.7.1.0 The snapshot workflow and interface in the Arnold RenderView has multiple enhancements and behaviours.

OCIO environment variable behavior follows 3ds Max color management settings

MAXtoA 5.7.1.0 The color management setup in 3ds Max 2025 has explicit modes to use different OCIO configurations: a default mode, a custom mode, and a mode to follow the OCIO environment variable. MAXtoA passes this mode setting on to the Arnold renderer so that Arnold uses the OCIO environment variable override only when 3ds Max is explicitly set in the OCIO - Environment Variable mode. (MAXTOA-1737)

Improved export with USD for 3ds Max

MAXtoA 5.7.0.0 Several improvements have been added when using the Arnold template in MaxUSD. The scene hierarchy is now aligned better between MAXtoA and 3ds Max USD, instanced objects are now exported correctly, and inherited transformation matrices are now exported correctly. (MAXTOA-1679, MAXTOA-1680, MAXTOA-1681).

Imager setups can be exported and imported:

7.2.5 A set of imagers can be exported to and imported from arnold files (.ass, usd), for exchange between scenes or to use as presets.

Imagers automatically sorted in a logical order

7.2.5 When you add imagers, they are automatically applied in the most useful order (for example, Light Mixers go first in the list). You can still re-order them manually if necessary.

Object selection in Arnold RenderView

7.2.5 You can select objects in the Arnold RenderView after a production render, as well as after an an interactive rendering.

Ramp shader

HtoA 6.3.3 Improved UI and new linkable inputs (HTOA-2629)

Arnold ROP

HtoA 6.3.3 Now saves deform_keys to universe options (HTOA-2620) AtNode* options = AiUniverseGetOptions(universe); const int deform_keys = AiNodeGetInt(options, 'deform_keys');

OSL VOP

HtoA 6.3.3 Added a manual Compile button (HTOA-1733) Node inputs and outputs are updated on scene load, even in manual cook mode (HTOA-1733)

Edit Arnold Material Network LOP

HtoA 6.3.1 New LOP that lets you edit Arnold materials in Solaris (HTOA-2070)

OIDN Denoiser enabled by default

HtoA 6.3.1 New scenes (in both Solaris and classic HtoA) automatically include a default denoiser imager network. You can disable the default denoiser by setting ARNOLD_DEFAULT_DENOISER=0 (HTOA-2503)

Houdini Package Support

HtoA 6.3.1 The HtoA installer now generates a Houdini package file instead of editing houdini.env. HTOA-1859

Light instancing

HtoA 6.2.5 You can now instance and render Light SOPs. Solaris lights, or lights created by a procedural, are not supported yet. (HTOA-693)

Support multiple packed primitives per alembic

HtoA 6.2.5 Scenes using Houdini Alembic packed primitives now generate much smaller amounts of data in Arnold, creating a single alembic node to represent multiple packed primitives. This reduces the time to process the generated secne significantly, in some cases giving a 64x speed up on scene translation, and an exponentional reduction in file sizes. See table below. (HTOA-1920)

Arnold procedural nodes now trigger OnCreated.py scripts

HtoA 6.2.5 As with the legacy Arnold Procedural node any new Arnold Procedural nodes can trigger the oncreated event see the houdini asset event documentation for further details (HTOA-2131)

Post Translation Hook

HtoA 6.2.5 Added a post-translation Python callback to the Arnold ROP, With this callback, you can directly edit the Arnold universe before the render begins. (HTOA-657)

Support for husk thread count argument

HtoA 6.2.5 You can set the number of render threads on the husk command line with --thread or --j. (ARNOLD-13299)

Cinema 4D Particles

C4DtoA 4.7.2 You can now render particles generated by the new Cinema 4D particle system released in Cinema 4D 2024.4. (C4DTOA-3184)

Spline surface in Arnold Scatter

C4DtoA 4.7.1 You can now scatter instances over a Spline surface with the Arnold Scatter object. Deformed splines are not supported. (C4DTOA-2178)

Multiple surfaces in Arnold Scatter

C4DtoA 4.7.1 The Arnold Scatter object now distributes instances over all polymesh and spline surfaces within the specified object tree. You can use a Null object to group your objects or you can use an object generator such as a Cloner. (C4DTOA-3154)

Push apart based on shape bounds in Arnold Scatter

C4DtoA 4.7.1 New push apart mode is added to Arnold Scatter that does not allow instance bounds to collide when distributing instances on a surface. (C4DTOA-3014)

Enable denoising in new scenes

C4DtoA 4.7.1 When selecting Arnold as the active renderer, an Intel® Open Image Denoiser imager (OIDN) is now automatically created and added to the scene, thus you render with denoising enabled. Automatic denoising can be turned off from the Preferences. (C4DTOA-3151)

Arnold Procedural displays curves in the viewport

C4DtoA 4.7.1 Curves in an Arnold procedural (ASS, USD, and AlembicC) are displayed in the viewport when the Display Mode is set to Wireframe or Shaded. (C4DTOA-3141)

Shape index via Effectors in Arnold Scatter

C4DtoA 4.6.8 The Arnold Scatter object now reads the shape index (Modify Clone parameter) from its Effectors in the new 'effectors' Shape Mode. You can use Fields via the Plain Effector or Cinema 4D shaders via the Shader Effector to control the distribution of shape instances across the surface. (C4DTOA-3010)

Instance visibility via Effectors in Arnold Scatter

C4DtoA 4.6.8 The Arnold Scatter object now reads visibility from its Effectors. That means the Hide mode of the Push Apart Effector is now supported. (C4DTOA-3011)

New isolate selected options in the IPR

C4DtoA 4.6.8 You can now choose which type of nodes are filtered by isolate selection in the IPR window. Objects and lights are filtered by default, material selection is ignored. Settings are available from the context menu of the toolbar button and the Render menu. (C4DTOA-3094)

Improved IPR render time and interactivity

C4DtoA 4.6.7 As a result of an optimization in the display logic of interactive renders, render times in the IPR are now about 1.2x faster, depending on complexity and sampling settings. The improvement is most significant in simple scenes when rendering multiple AOVs on the GPU. (C4DTOA-3075)

Procedural and volume animation start loop

C4DtoA 4.6.7 You can now control looping of frames before the start of an animated procedural or volume, not just frames after the animation. For instance you can freeze the first frame before the animation. (C4DTOA-3087)

Support custom procedurals in UsdIn

KtoA 4.3.3.0 Custom procedurals defined in a USD file as ArnoldProceduralCustom primitives are now imported through UsdIn as renderer procedurals. (KTOA-1006)

ArnoldOutputManager node

KtoA 4.3.1.0 The new ArnoldOutputManager simplifies the creation of render output channels and render outputs for Arnold, providing an Arnold-style view of filters, AOVs, outputs, and drivers. You can use the ArnoldOutputManager together with existing ArnoldOutputChannelDefine and RenderOutputDefine nodes if you need to edit specific attributes of the outputs afterwards. (KTOA-409)