[Tip] Save a few threads for yourself

Posted on February 18, 2016 by xsisupport

As of Arnold 4.2.12.0, you can specify a negative number of threads, and Arnold will leave that many threads free. So, for example, if you want to leave two threads free for Maya while the IPR view is running, you would set the thread count to -2.

mtoa_threads

On a machine with 4 cores and 8 logical cores (aka threads):

| running on StephenBlair-PC, pid=16888
| 1 x Intel(R) Xeon(R) CPU E3-1240 V2 @ 3.40GHz (4 cores, 8 logical) with 16338MB
| Windows 7 Professional Service Pack 1 (version 6.1, build 7601)

You would then see that Arnold uses only 6 logical cores:

|  starting 6 bucket workers of size 64x64 ...

The advantage of the negative thread count is that you don’t have to know how many logical cores your machine has; you just need to know how many you want to keep free.

The case of the blue render view

Posted on February 17, 2016 by xsisupport

Reason #35 why you should check the Arnold log

In this case, a scene that used to render yesterday, now just resulted in a blue render view, like this:

blue_render_view

Anytime the render view doesn’t update when your render, you can be fairly sure there’s some ERROR in the Arnold log.

In this case, the problem was a broken path to the IES file used by a photometric light. In the Arnold log, there was this ERROR:

00:00:04 870MB ERROR | [photometric] can't open C:/Assets/IES/example.ies

It’s easy to say “check the log”, but where do you find the log? It’s not like there’s a nice, color-coded button (red for error) on the render view UI that will pop up the log for you.

On Windows, you should see the Arnold log in the Output Windows. However, I find that this happens only when I start Maya from the command line. If I start Maya from the Windows Start menu, the Arnold log messages don’t show up in the Output Window. So I have to enable file logging, and check the log file.
On OSX and Linux, you’ll also have to enable file logging, unless you start Maya from a terminal.

Update: For Google:

Arnold renders a black screen
Arnold renders a blue screen

WARNING : [ass] node name already in use

Posted on February 9, 2016 by xsisupport

Shader nodes must have unique names.

So if you’re using standins, each standin ASS file has to have unique shader node names. Otherwise you’ll get unexpected results when you render, like all standins having the same shading, or some “flickering” in animation if the order of standin loading changes.

In the Arnold log, look for “node name already in use” warnings:

WARNING | [ass] standin_01.ass line 50: node name "aiStandard1SG" already in use
WARNING | [ass] standin_01.ass line 58: node name "aiStandard1" already in use
WARNING | [ass] standin_01.ass line 118: node name "file1" already in use
WARNING | [ass] standin_01.ass line 147: node name "aiNoise1" already in use

If each standin should look different, you need to have unique shader names in each ASS file. If you’re using MtoA, that includes the name of the SG node (for example, aiStandard1SG).

[C4DtoA] Installing C4DtoA in a custom location

Posted on February 4, 2016 by xsisupport

The C4DtoA installer puts the C4DtoA plugin in the default location: the plugins folder of the Cinema 4D install.

If you want to put C4DtoA somewhere else, like a shared network location, you can use the C4D_PLUGINS_DIR environment variable to point to your custom plugin location.

For example, on Windows I moved C4DtoA to a different drive and then set my environment like this:

set C4D_PLUGINS_DIR=F:\plugins
set PATH=F:/plugins/C4DtoA/arnold/bin;%PATH%

Note that I had to set PATH so C4D could find ai.dll, and that I had to use forward slashes (on Windows, C4D doesn’t like backslashes in the PATH and drops them).

On Windows, the C4DtoA installer puts a second copy of ai.dll in the C:\Program Files\MAXON\CINEMA 4D R17, so you’ll have to remove that ai.dll, and use PATH to point to the ai.dll in the C4DtoA arnold/bin folder.

Portable ASS files with relative paths and the Texture Search Path

Posted on January 29, 2016 by xsisupport

You can make your ASS files portable across different platforms by using relative paths and the texture search path. For example, if all textures are specified by relative paths like “textures/noicon.tx”, then you just have to set options.texture_searchpath to specify the location of the textures folder.

For example

kick -set options.texture_searchpath //server/project/ -dp -dw example.ass

Or if the texture search path is set to an environment variable

export ARNOLD_TEXTURE_PATH=//server/project
./kick example.ass

To use relative paths for texture file names in nodes like MayaFile, aiImage, aiPhotometricLight, and aiSkydomeLight, you just need to do the following:

Put a relative path in the file name box (for example, in Photometry File box of an aiPhotometricLight node, or the Image Name box of an aiImage node)
Set the Texture Search Path (Render Settings > System > Search Paths)
Clear the Absolute Texture Paths check box

You can put multiple locations, using either : or ; to separate the paths (Arnold supports both separators on all platforms: OSX, Linux, and Windows)

You can use environment variables by putting the environment variable name in square brackets. For example:

"[ARNOLD_TEXTURE_PATH]:C:/Assets/IES/;C:/maya/projects/Support/sourceimages"

Forward slashes work on all platforms.

MtoA appends the current project’s sourceimages folder to the texture search path.

Why can’t I use kick -set options.shader_searchpath ?

Posted on January 27, 2016 by xsisupport

You may wonder: why can’t I use kick -set options.shader_searchpath to tell Arnold where to find shaders?

Well, it’s because kick loads the ASS file first, then applies the kick -set parameter overrides. And also, Arnold when loads an ASS file, Arnold automatically loads shaders from the shader_searchpath as soon as Arnold loads the options node.

Here’s the sequence of events:

kick loads all plugins specified by -l or by ARNOLD_PLUGIN_PATH before it loads the ASS file
kick loads the ASS file. When Arnold loads the options node, Arnold automatically loads all plugins specified by options.shader_searchpath.That’s why the options node is at the top of an ASS file: so Arnold can load any required shaders before loading the shader nodes. It you move the options to bottom of the ASS file, the shader nodes in the ASS file won’t be loaded.
Finally, after all the nodes are loaded, the -set parameter overrides are applied. At this point, it’s too late for any shaders from the -set options.shader_searchpath loacation. The corresponding nodes were already discarded during the loading of the ASS file.

WARNING mtoa_shading_groups: unresolved reference

Posted on January 25, 2016 by xsisupport

Any time you see “node … is not installed” and “unresolved reference” warnings when you try to kick an ASS file exported from Maya, the problem is missing MtoA shaders.


00:00:00 18MB WARNING | [ass] line 259: node "MayaFile" is not installed
00:00:00 18MB WARNING | [ass] line 288: node "MayaShadingEngine" is not installed

00:00:03 23MB WARNING | [ass] line 238: pSphereShape1.mtoa_shading_groups: unresolved reference to 'aiStandard2SG'
00:00:03 23MB WARNING | [ass] line 137: aiSkyDomeLightShape1.color: unresolved reference to 'file1'
00:00:03 23MB WARNING | [ass] line 188: pPlaneShape1.shader: unresolved reference to 'aiStandard1SG'
00:00:03 23MB WARNING | [ass] line 197: pPlaneShape1.mtoa_shading_groups: unresolved reference to 'aiStandard1SG'
00:00:03 23MB WARNING | [ass] line 229: pSphereShape1.shader: unresolved reference to 'aiStandard2SG'

When you render with kick, you need to specify the location of the MtoA shaders. You can do this several ways:

Set the ARNOLD_PLUGIN_PATH environment variable. For example:

export ARNOLD_PLUGIN_PATH=/home/render/solidangle/mtoa/2016/shaders

set ARNOLD_PLUGIN_PATH=C:\solidangle\mtoadeploy\2016\shaders

Use the kick -l flag to specify the MtoA shader location.
In Maya, set the Shader Search Path in the Arnold Render Settings, then export the ASS file.

[Arnold] Rolling shutter in a nutshell

Posted on November 5, 2015 by xsisupport

What’s rolling shutter? It’s an effect, or artifact, that looks like like this:

Rolling shutter means that the image isn’t captured all at once, but one scanline at a time:

Lee posted a video walk through of how to get the rolling shutter effect with Arnold. He used C4DtoA, but it’s basically the same recipe in any of the Arnold plugins:

Your geometry has to be spinning fast (like a propeller 😉
Select your camera, and enable Rolling Shutter. Leave the duration at 0.
In the Render Settings, enable motion blur (you don’t need deformation blur, or camera blur).
Adjust the number of motion keys, and the shutter length, to taste. As you increase the shutter length to exaggerate the effect, you’ll need more motion keys.

Update: And here’s some more interesting experiments with the rolling shutter effect

[Arnold] Tips for reducing noise when rendering interior scenes with indirect lighting

Posted on October 29, 2015 by xsisupport

Indirect lighting of interior scenes can be a challenge, but there are some things you can do. In this post, we’ll give you some quick tips, but you can find more detailed information on support.solidangle.com, both for interior lighting and for troubleshooting noise.

Avoid the Skydome and use a Sky background and Quad lights

Instead of using a Skydome light, use a Sky for the background and quad lights for the light coming in through the windows. The quad lights should just barely cover the entire window.

If there’s anything visible outside the window, you may want to put a spot light on them. Just be careful not to let the spot light go into the room.

Use a distant light to simulate beams of light coming into the room

A distant_light is an easy-to-use option that perfectly matches sun light.

Spot lights don’t produce realistic sun beams since the beams look like they’re expanding, which sun beams don’t do. Moving the spot light further back, and also making sure it’s no larger than it needs to be to illuminate the window, will reduce noise and make it look more realistic.

Don’t put lights too close to the windows

If a light is too close to the window, that means the light hitting the window area is significantly more concentrated and so much brighter than the light hitting the far side of the room and so this produces more noticeable noise.

Make sure your materials are physically based

For example, don’t shade the room Standard shaders with a Diffuse weight of 1, and Diffuse color full white (1 1 1). I don’t think there’s any material known to man that is this reflective. Lowering the Diffuse weight to 0.7 will roughly match white paint and it will also get rid of noise. If it’s too dark, then try increasing the intensity of the lights, increase the number of diffuse bounces, or increase the camera’s exposure.

For a richer look, avoid fake lights inside the room

Consider getting rid of any fake lights you may have inside the room, and instead increase the number of diffuse and glossy bounces in order to get an even more realistic look, not to mention make the lighting easier. Doing that does increase render times, unfortunately, but does give a richer look.

hat tip: Thiago

[Arnold] System requirements

Posted on June 17, 2015 by xsisupport

In general, Arnold is going to work on pretty much any 64-bit system where Houdini, Maya, Cinema 4D, or Softimage works. However, there are some minimum OS requirements:

OSX 8 or later (as of Arnold 4.2.7.0)
Windows 7 or later (as of Arnold 4.2.3)
Linux with at least glibc 2.12 and libstdc++ 3.4.13 (gcc 4.4.7). This is equivalent to RHEL/CentOS 6 (as of Arnold 4.2.6)
CPUs need to support the SSE4.1 instruction set (as of Arnold 4.2.16.2)

Other than that, Arnold works on Intel and AMD processors, and has no graphic card or GPU requirements, since Arnold is a CPU-based renderer.

Last updated: 19 June 2017

Arnold Support Corner

Tips, tricks, and troubleshooting help from Steve "xsisupport" Blair

Category Archives: Arnold