9 December 2016

This is a feature release, with a new portal mode for skydome light and introducing the complex_ior, thin_film and flakes shaders.

  1. Get the install files on Solid Angle Downloads.
  2. Follow these installation instructions.

This release uses Arnold and OpenVDB 3.1.0.

Binaries available for the following Houdini, Houdini FX, Houdini Indie and Houdini Education production builds:

  • 15.5.673
  • 15.5.632
  • 15.5.607

and for the following platforms:

  • Linux x86_64 (gcc4.8)
  • Windows 7 x64 (vc14)
  • Mac OS X 10.8+ (clang7.3)

Please note that Houdini Apprentice does not support third party renderers and thus cannot run HtoA.

  • Portal mode: Skydome lights now have a portal_mode parameter with options off, interior_only and interior_exterior to respectively turn off portals, block any light outside portals for interior only scenes, and let light outside portals through for mixed interior and exterior scenes. Blocking light outside portals more predictably reduces noise for interior only scenes, but is biased. (core#5601, htoa#847)
  • Complex IOR shader: This shader can be used to render materials with complex index of refractions. The Standard shader can compute the Fresnel effect for dielectric materials like plastic and glass based on the refractive index of the material (n), however metals have a more complicated Fresnel reflective curve that depends also on another parameter called the extinction coefficient (k). You can either the n & k physical parameters for R, G , B or use the artistic Reflectance & Edgetint colors to define the Fresnel. The shader also comes with a number of presets for common metals. This shader should be used as a specular/reflection color map in the Standard shader, with the Fresnel option disabled, as it does its own Fresnel calculations. (csp#101)

  • Thin film shader: This shader reproduces the effect of thin film interference on a surface. It can be linked to the Specular or Reflection color of a Standard shader with the Fresnel option disabled, as the shader does its own Fresnel calculations. (csp#103)
  • Flakes shader: This shader creates a procedural flake normal map that can be used for materials such as car paint. Note that the map does not perform any filtering, so small flakes require more AA samples to become clean. (csp#102)
  • Custom UV set for ramp shaders: The ramp_rgb and ramp_float shaders now allow the selection of a custom UV set (csp#104)
  • Improved oriented curves mode: The oriented curves mode will now produce an actual 3D surface when rendering, making it more suitable for shapes like grass and feathers. This replaces the previous behavior that was based on the 2D ribbon mode. (core#5532)

  • Faster minimum pixel width: min_pixel_width for curves and points is now significantly faster in certain situations. (core#5249)

  • New output image metadataarnold/camera/near_clip and arnold/camera/far_clip have been added to output image EXR metadata. (core#3175)
  • File handle limits: We now report the file handle limit used by arnold at the top of the log and if the limit is hit, we print out a list of all the open files in order to aid in determining why there are so many files open at the same time. (core#5236, core#5237, core#5238)
  • Auto-detect threads respects Linux CPU taskset: On Linux, if the Arnold process is run under a restricted CPU set, such as from taskset or numactl, then setting the number of threads to 0 will cause Arnold to use the number of cores it's been assigned, instead of the total number of logical cores in the system. (core#5283)
  • Fixed volume and implicit bounding box calculation slow in batch when displayed as volumes in the viewport. (htoa#845)
  • Fixed ground projection in specular with the shadow_matte shader. (csp#99)
  • Fixed conflict with the built-in shadow_matte AOV. (csp#98)
  • Fixed makeTxExecute() exception in IPR when selecting a non-TX texture in the Image shader. (htoa#840)

Incompatible changes
  • The state_rgb shader has been removed as the shader globals it exposed did not make sense outside of a light loop or would have been unreliable to use. (csp#100)


See also the Arnold release notes for the full list of core enhancements and fixes.

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