If you see messages like this when you try to use HtoA
Syntax error: Missing parentheses in call to 'print'
or
AttributeError: '_Environ' object has no attribute 'has_key'
or
CreateProcess failed
that means the you have the Python 3 version of Houdini installed.
HtoA 5.6.1 and older do not support Python 3 yet, so you need to download and install the Python 2.7 version of Houdini.
You can get the Python 2.7 version of Houdini here: https://www.sidefx.com/download/daily-builds/?production=true
To denoise AOVs, you need to add variance AOVs:
When you denoise the AOVs, you’ll see something like this in the Arnold Denoiser log:
C:\Program Files\Autodesk\Arnold\maya2020\bin\noice -i C:/project/images/denoiser_test.0002.exr -o C:/project/images/denoiser_test.0002_denoised.exr -ef 0 -sr 9 -pr 3 -v 0.5 -l diffuse -l direct -l indirect -l specular Denoising image C:/project/images/denoiser_test.0002.exr ------------------------ (1/1) noice 6.2.0.1 [903992ac] - the Arnold denoiser Using 48 threads. Loading images... Loading file "C:/project/images/denoiser_test.0002.exr". Using feature AOV 'diffuse_albedo' with filter 'gaussian_filter' Using feature AOV 'N' with filter 'gaussian_filter' Using feature AOV 'Z' with filter 'gaussian_filter' Working with 1 frame at 960x540 Will denoise AOV "RGBA", using associated variance Output file will be "C:/project/images/denoiser_test.0002_denoised.exr" Will denoise AOV "diffuse", using associated variance Output file will be "C:/project/images/denoiser_test.0002_denoised.exr" Will denoise AOV "direct", using associated variance Output file will be "C:/project/images/denoiser_test.0002_denoised.exr" Will denoise AOV "indirect", using associated variance Output file will be "C:/project/images/denoiser_test.0002_denoised.exr" Will denoise AOV "specular", using associated variance Output file will be "C:/project/images/denoiser_test.0002_denoised.exr" Start denoising (patch radius 3, search radius 9, variance 0.5) Denoising RGBA Denoising diffuse Denoising direct Denoising indirect Denoising specular Finished denoising Saving image C:/project/images/denoiser_test.0002_denoised.exr (960 x 540 x 16)
Here’s a simple kick trick to get a list of AOVs and LPEs.
The -laovs flag lists all the AOVs in the loaded scene, but if you give kick no input, you’ll get a list of all built-in AOVs defined by Arnold.
For example, on Windows, run kick -laovs -i Nul
On Linux or macOS, run kick -laovs -i /dev/null
kick -laovs -i Nul
Available aovs:
Type: Name: LPE:
--------------------------------------------------------------
VECTOR2 motionvector (~)
RGBA RGBA C.*
VECTOR N (~)
FLOAT Z (~)
RGB direct C[DSV]L
RGB indirect C[DSV][DSVOB].*
VECTOR Pref (~)
RGB albedo C[DSV]A
RGB emission C[LO]
RGB diffuse_direct C<RD>L
RGB background CB
RGB denoise_albedo ((C<TD>A)|(CVA)|(C<RD>A))
RGB sss_albedo C<TD>A
RGB specular_albedo C<RS[^'coat''sheen']>A
RGB diffuse C<RD>.*
FLOAT cputime (~)
RGB diffuse_indirect C<RD>[DSVOB].*
RGB sss_indirect C<TD>[DSVOB].*
RGB diffuse_albedo C<RD>A
RGBA shadow_matte
FLOAT volume_Z (~)
RGB specular C<RS[^'coat''sheen']>.*
RGB coat_direct C<RS'coat'>L
RGB specular_direct C<RS[^'coat''sheen']>L
RGB specular_indirect C<RS[^'coat''sheen']>[DSVOB].*
RGB volume_direct CVL
RGB coat C<RS'coat'>.*
RGB coat_indirect C<RS'coat'>[DSVOB].*
RGB coat_albedo C<RS'coat'>A
RGB sheen C<RS'sheen'>.*
RGB transmission C<TS>.*
RGB transmission_direct C<TS>L
RGB transmission_indirect C<TS>[DSVOB].*
VECTOR2 AA_offset (~)
RGB transmission_albedo C<TS>A
VECTOR P (~)
RGB sheen_direct C<RS'sheen'>L
RGB volume CV.*
RGB sheen_indirect C<RS'sheen'>[DSVOB].*
NODE shader (~)
RGB sheen_albedo C<RS'sheen'>A
RGB sss C<TD>.*
RGB sss_direct C<TD>L
RGB volume_indirect CV[DSVOB].*
RGB volume_albedo CVA
FLOAT A (~)
FLOAT ZBack (~)
RGB opacity (~)
RGB volume_opacity (~)
FLOAT raycount (~)
UINT ID (~)
NODE object (~)
FLOAT AA_inv_density (~)
RGBA RGBA_denoise (~)
--------------------------------------------------------------
(~) No opacity blending
You can export a Bifrost scene to an Arnold ass file and then render it with kick.
Just use the -l flag (or the ARNOLD_PLUGIN_PATH environment variable) to point to the Arnold plugins that comes with the Bifrost install. For example, on Windows:
kick -v 5 -dp bifrost_aeroColors.ass -l "C:\Program Files\Autodesk\Bifrost\Maya2020\2.2.0.2\bifrost\arnold-6.2.0.0"
In the Arnold log, we see that Arnold loads the procedural nodes for Bifrost:
00:00:00 88MB | loading plugins from C:\Program Files\Autodesk\Bifrost\Maya2020\2.2.0.2\bifrost\arnold-6.2.0.0 …
00:00:00 100MB | arnold_bifrost.dll: bifrost_graph uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_object uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_multires_volume uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_multires_implicit uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_volume uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_points uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_implicit uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_polymesh uses Arnold 6.2.0.0
00:00:00 100MB | arnold_bifrost.dll: bifrost_blocks uses Arnold 6.2.0.0
00:00:00 100MB | loaded 9 plugins from 1 lib(s) in 0:00.06
In other applications, like CINEMA 4D or Houdini or Katana, you can do the same thing by setting the Plugin Search Path.
If you see this error in your Arnold log, it most likely means that you have more than 256 per-face shaders. Arnold has a hard limit of 256 shaders that can be assigned to a single object.
[polymesh] /pPlane1/pPlaneShape1: out-of-range shader index (5/3)
You may also see this warning if you have a large number of objects merged into one single object (for example, an Alembic archive that consists of many objects). In some cases, an Alembic archive like that may have more than 256 shaders assigned to the sub-objects.
The built-in N AOV is in world space. So how to get a tangent-space N AOV?
Like this:
In brief, I read the N AOV, transform the normals from world to tangent space, and then map the normal values to the range 0.5, 1 (I used the range node here, but I could have used Add and Multiply to do the same thing).
Here’s the shader tree. You can save this in a .ass file and import it into Maya or whatever application you use. Then set up an AOV shader to write the custom Ntangent AOV
range
{
name aiRange1
input space_transform
output_min 0.5
}
space_transform
{
name space_transform
input read_N_AOV
type "normal"
to "tangent"
tangent 1 0 0
normal 0 1 0
normalize on
}
aov_read_rgb
{
name read_N_AOV
aov_name "N"
}
aov_write_rgb
{
name defaultArnoldRenderOptions/aov_write_rgb_Ntangent
aov_input aiRange1
aov_name "Ntangent"
}
The Optix imager can denoise the beauty and any other AOV.
The so-called layer selection tells the imager what AOVs to denoise. For example, if you want to denoise both the beauty and the coat AOVs, enter RGBA or coat in the Layer Selection text box.
Using AOV names with or is an easy way to select multiple AOVs.
You can also use wildcard characters (such as *, ., and []) to select AOVs (this is what is called glob in the docs). For example:
| * | Selects all AOVs |
| RGBA_* | Selects all light group AOVs for the beauty (for example, RGBA_default, RGBA_key, and so on) |
| RGBA_light0[135] | Selects RGBA_light01, RGBA_light03, and RGBA_light05 |
| RGBA_light0. | The period (.) matches any single character, so this selects RGBA_light00 through to RGBA_light09. RGBA_light0[1-9] does the same thing. |
You can even use regular expressions for more complicated selections. But in general, using or and wildcards should be more than enough.
First, set up your AOVs like this:
Then run noice like this:
set IMAGES="C:\Users\Stephen Blair\Documents\3ds Max 2020\renderoutput\denoiseme" set ARNOLD_BIN=S:\solidangle\arnold\Arnold-6.0.2.0-windows\bin %ARNOLD_BIN%\noice ^ -ef 2 -sr 2 -pr 2 -v 0.5 ^ -i %IMAGES%/AOVs0003.exr ^ -i %IMAGES%/variance0003.exr ^ -l diffuse ^ -l specular ^ -o %IMAGES%/denoised_AOVs0003.exr
The AOVs and variance AOVs are in separate EXRs
That’s necessary to be able to have different filters for the same AOV in MAXtoA
Tip: In the Windows command prompt, you can use ^ (Shift + 6) character to indicate line continuation, and break long commands into multiple lines. You can also use ^ in in a batch file.
New with Arnold 6.0.4 is path mapping.
All you have to do is create a json file that looks something like this:
{
"windows": { "S:/": "\\server\projects\" },
"mac": { "S:/": "/Volumes/projects/"},
"linux": {"S:/": "/mnt/projects/"}
}
and then set ARNOLD_PATHMAP to point to the json path mapping file
When you render a frame, here’s what Arnold does for file paths:
When Arnold loads an ass file, Arnold replaces all backslashes ( \ ) with forward slashes ( / )
When Arnold uses a parameter, Arnold expands all environment variable references, which look like this: [MY_TEXTURE_PATH]
After Arnold expands environment variables, Arnold applies the path-mapping rules specified by the Arnold pathmap file.
Arnold expands environment variable expansion and maps paths for:
You can automatically remap paths at render time using a pathmap file.
To use a pathmap
ARNOLD_PATHMAP environment variable to point a pathmap fileThe pathmap file is a json file. For example:
{
"windows": { "S:/": "\\server\projects\" },
"mac": { "S:/": "/Volumes/projects/"},
"linux": {"S:/": "/mnt/projects/"}
}
Path mapping uses regular expressions. The general format of an entry is this:
{
"windows": { "regular expression": "replacement string" },
}
For example, this pathmap replaces all drive mappings like E:/ and S:/ with //SERVER/
{
"windows": { "[A-Z]:/": "//SERVER/" },
}
Arnold converts backslashes ( \ ) to forward slashes ( / ) when it loads the ASS file.
Path mapping happens after that, so pathmaps never have to deal with backslashes.
There can be multiple mappings for each OS:
{
"windows": { "[A-Z]:": "//SERVER", "sourceimages/": "textures/"},
}
Arnold Support Corner 