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Quick Summary

Arnold GPU supports complex shading networks, SSS, hair, atmospherics, instancing, and procedurals.
With the same settings, GPU renders will currently be noisier than CPU renders since GPU renders are "non-splitting" (i.e. one path per camera/AA sample). Accordingly, to achieve equivalent noise the AA sample count will need to be increased in GPU renders. Adaptive rendering is fully supported.
Standard Surface, Standard Hair, and Standard Volume are supported, with some limitations (see the table below).
OSL is supported, with some limitations currently (see below).
OpenVDB volumes are supported, with some limitations currently (see below).
Volume displacement is supported, with some limitations currently (see below).
Floating-point textures are converted to half-float. Filename attribute tags are supported. Mipmap bias is not supported.
Light linking is not supported.
Limited AOV support.
Light groups, shadow groups, trace sets are not supported.
Custom procedurals, drivers, color managers are supported.
Custom shaders, cameras, filters, BSDFs are not supported.
Noice is not supported with Arnold GPU renders (because the variance filter is not supported on Arnold GPU)

OSL

Initial support for OSL has been added to the GPU renderer. As in the CPU renderer, you can mix and match OSL and Arnold shaders in the same shading network. Note that this initial support is still not complete and currently has a number of limitations as listed below.

Closures

Supported closures include:

Emission
Diffuse
Reflection
Refraction
Translucent
Oren-Nayar
Sheen
SSS
Metal & Microfacet

Shading operations

Currently, there is limited support for shading operations, as follows:

Some matrix operations are unsupported.
Texture, trace are currently unsupported.

OpenVDB

Initial support for OpenVDB has been added to the GPU renderer. In this initial implementation, each VDB grid is loaded to GPU in a dense format. While this matches the CPU renderer visually quite well and is feature-complete, the memory consumption can be larger due to the lack of sparse representation. The rendering speed may be slower than CPU in cases with high opacity volumes, as the GPU implementation does not skip empty space as efficiently as the CPU version. The match with CPU will become increasingly good as the step-size parameter is reduced.

Volume displacement

Initial support for volume displacement has been added to the GPU renderer. The rendering speed may be slower than CPU in cases with high opacity volumes, as the GPU implementation does not skip empty space as efficiently as the CPU version. The match with CPU will become increasingly good as the step-size parameter is reduced.

Supported Features and Known Limitations

Feature	GPU Support	Notes
Cameras
cyl_camera	Yes
fisheye_camera	Yes
ortho_camera	Yes
persp_camera	Yes
spherical_camera	Yes
uv_camera	Yes
vr_camera	Yes
Color Managers
color_manager_ocio	Yes
color_manager_syncolor	Yes
Drivers
cryptomatte_manifest_driver	No
driver_deepexr	No
driver_exr	Yes
driver_jpeg	Yes
driver_png	Yes
driver_tiff	Yes
Filters
blackman_harris_filter	Yes	One single filter for all AOVs.
box_filter	Yes	One single filter for all AOVs.
gaussian_filter	Yes	One single filter for all AOVs.
triangle_filter	Yes	One single filter for all AOVs.
All other filters	No	Fallback to box filter. One single filter for all AOVs.
Lights
cylinder_light	Yes
disk_light	Yes
distant_light	Yes	Light groups not supported.
mesh_light	Yes	Light groups not supported.
photometric_light	No
point_light	Yes	Light groups not supported.
quad_light	Yes	Light groups not supported.
skydome_light	Yes	Light groups not supported.
spot_light	Yes	Light groups not supported.
Operators
collection	Yes
disable	Yes
include_graph	Yes
materialx	Yes
merge	Yes
set_parameter	Yes
set_transform	Yes
switch_operator	Yes
options	Yes
override	Yes
Shaders
abs	Yes
add	Yes
ambient_occlusion	Yes	Trace sets are not supported.
aov_write_float	No
aov_write_int	No
aov_write_rgb	No
aov_write_rgba	No
atan	Yes
atmosphere_volume	Yes
barndoor	Yes
blackbody	Yes
bump2d	Yes
bump3d	Yes
c4d_texture_tag	Yes
c4d_texture_tag_rgba	Yes
cache	Yes	This is a no-op on GPU.
camera_projection	Yes
car_paint	Yes
cell_noise	Yes
checkerboard	Yes	UV sets are not supported.
clamp	Yes
clip_geo	No
color_convert	Yes
color_correct	Yes
color_jitter	Yes
compare	Yes
complement	Yes
complex_ior	Yes
cross	Yes
cryptomatte	No
curvature	Yes	Trace sets are not supported.
divide	Yes
dot	Yes
exp	Yes
facing_ratio	Yes
flakes	Yes
flat	Yes
float_to_int	Yes
float_to_matrix	No
float_to_rgb	Yes
float_to_rgba	Yes
fog	Yes
fraction	Yes
gobo	Yes
image	Yes	All textures converted to half-float. mipmap bias is not supported.
is_finite	Yes
lambert	Yes
layer_float	Yes
layer_rgba	Yes
layer_shader	Yes
length	Yes
light_blocker	Yes
light_decay	Yes
log	Yes
matrix_interpolate	No
matrix_multiply_vector	Yes	The matrix parameter is not linkable on GPU.
matrix_transform	No
matte	No
max	Yes
maya_layered_shader	Yes
min	Yes
mix_rgba	Yes
mix_shader	Yes
modulo	Yes
motion_vector	No
multiply	Yes
negate	Yes
noise	Yes
normal_map	Yes
normalize	Yes
osl	Yes	Some limited support for closures and shading operations.
passthrough	Yes
physical_sky	Yes
pow	Yes
query_shape	Yes
ramp_float	Yes	Connected colors and positions not supported.
ramp_rgb	Yes	Connected colors and positions not supported.
random	Yes
range	Yes
ray_switch_rgba	Yes
ray_switch_shader	Yes
reciprocal	Yes
rgb_to_float	Yes
rgb_to_vector	Yes
rgba_to_float	Yes
round_corners	Yes	Trace sets are not supported.
shadow_matte	Yes	This initial version has a number of limitations currently, including: no support for indirect lighting, no AOV generation, and possibly incorrect self-reflections in shadow-matte objects.
shuffle	Yes
sign	Yes
space_transform	Yes	Camera and screen spaces are not supported.
sqrt	Yes
standard_hair	Yes	ID AOVs are not supported extra depth and extra samples are not supported
standard_surface	Yes	ID AOVs are not supported. Diffusion SSS mode is not supported. Transmit AOVs is not supported (so, for example, you'll get solid white in the alpha for transmission)
standard_volume	Yes
state_float	Yes
state_int	Yes
state_vector	Yes
subtract	Yes
switch_rgba	Yes
switch_shader	Yes
toon	No
trace_set	No
trigo	Yes
triplanar	Yes
two_sided	Yes
user_data_float	Yes
user_data_int	Yes
user_data_rgb	Yes
user_data_rgba	Yes
user_data_string	No
utility	Yes	The wire, polywire, edgelength, pixelerror, nlights color modes are not supported.
uv_projection	Yes
uv_transform	Yes
vector_map	Yes
vector_to_rgb	Yes
volume_sample_float	Yes
volume_sample_rgb	Yes
wireframe	No
Shapes
box	Yes	Light groups, shadow groups, trace sets are not supported.
cone	No
curves	Yes	Light groups, shadow groups, trace sets are not supported. Oriented curves are not supported.
cylinder	No
disk	No
ginstance	Yes	Light groups, shadow groups, trace sets are not supported.
nurbs	Yes
plane	Yes	Light groups, shadow groups, trace sets are not supported.
points	Yes	Light groups, shadow groups, trace sets are not supported.
polymesh	Yes	Light groups, shadow groups, trace sets are not supported.
sphere	Yes	Light groups, shadow groups, trace sets are not supported.
implicit	No
volume_implicit	No
alembic	Yes	Light groups, shadow groups, trace sets are not supported.
procedural	Yes	Light groups, shadow groups, trace sets are not supported.
volume	Yes	Light groups, shadow groups, trace sets are not supported.
AOVs
AA_inv_density	Yes
ID	Yes
N	Yes
P	Yes
Pref	No
RGBA	Yes
Z	Yes
albedo	Yes
background	Yes
coat	Yes
coat_albedo	Yes
coat_direct	Yes
coat_indirect	Yes
cputime	Yes
diffuse	Yes
diffuse_albedo	Yes
diffuse_direct	Yes
diffuse_indirect	Yes
direct	Yes
emission	Yes
indirect	Yes
motionvector	No
opacity	Yes
raycount	Yes
shadow_matte	No
sheen	Yes
sheen_albedo	Yes
sheen_direct	Yes
sheen_indirect	Yes
specular	Yes
specular_albedo	Yes
specular_direct	Yes
specular_indirect	Yes
sss	Yes
sss_albedo	Yes
sss_direct	Yes
sss_indirect	Yes
transmission	Yes
transmission_albedo	Yes
transmission_direct	Yes
transmission_indirect	Yes
volume	Yes
volume_Z	No
volume_albedo	No
volume_indirect	No
volume_opacity	No
Custom plugins
BSDF	No
Camera	No
Color Manager	Yes
Driver	Yes
Filter	No
Shader	No
Procedural	Yes