Solid Angle Katana to Arnold 4.3.4.0

OpenPBR improvements
- View-dependent coat absorption: The coat lobe now more accurately models the absorption tinting at grazing angles, producing a slightly more realistic look. (ARNOLD-15377)


SSS color matching: The SSS model has been tuned to ensure that the color of dense SSS more closely matches the supplied subsurface_color, as required by the OpenPBR specification. (ARNOLD-15328). The following images compare diffuse base color with the subsurface colors of Standard Surface and OpenPBR Surface:
- top row: diffuse with a given base_color
- middle row: Standard Surface (dense) SSS, with same color assigned to subsurface_color
- bottom row: OpenPBR (dense) SSS, with same color assigned to subsurface_color


Scaling of emission luminance from nits to Arnold units: nits_per_unit was added to the options node, and OpenPBR Surface's emission_luminance (in nits) is internally scaled down by this nits_per_unit value (defaulting to 1000) to bring it into Arnold units. This ensures that the default soft-maximum of emission_luminance of 1000 nits corresponds to the former behavior of Standard Surface at emission 1. (ARNOLD-15364)
Faster startup times on GPU: We have made several optimizations to improve startup and scene update time on GPU. These improvements will be most noticeable on scenes with many objects. Startup times on Windows are also now on par with startup times on Linux. On a scene with 1 million instances, we see the following improvements when compared to the previous release. (ARNOLD-15271, ARNOLD-15279, ARNOLD-15310)


Handle update for OSL shader changes: Information about shaders linked to an OSL shader is stored when using interactive render mode, so that any change in those shaders will cause the OSL shader to be automatically updated. (ARNOLD-14983)
Duplicate node name warnings: Warnings are emitted when adding a node with a name that already exists or renaming an existing node to an empty string. (ARNOLD-12596)