Don’t download Arnold from your Autodesk Account.
That’s not what you need.
It’s the Arnold SDK.
You don’t need that.
You need an Arnold plugin, like MtoA or MAXtoA or C4DtoA or HtoA or KtoA or SItoA.
Get it here: https://www.solidangle.com/arnold/download/
You do need to register on solidangle.com
You can’t use your Autodesk logon
On Windows, run the MtoA installer with the flags /S /FORCE_UNINSTALL=1
MtoA-220.127.116.11-2018.exe /S /FORCE_UNINSTALL=1
You can use /D to specify a different install location.
On Linux, use the – – silent command line flags. Note the space between “- -” and “silent”.
sudo sh MtoA-18.104.22.168-linux-2017.run -- silent
The Linux installer will put MtoA in /opt/solidangle/mtoa/<maya version>. If you want to install in a different location, you can extract MtoA, and then set up your own script for installing MtoA.
On OSX, use the installer command:
sudo installer -pkg "MtoA-22.214.171.124-darwin-2017.pgk" -target /
Note that -target is a volume, not a folder.
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:
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.