How to start 3ds Max with a specific version of Corona Renderer? (using multiloaders with Corona 5 and newer)


Note: this guide can be used to launch Corona Renderer 5 or newer, and requires Corona Renderer 6 or newer installed. The old guide for Corona Renderer 4 and older can be found here: [link]



Sometimes you may want to: 

  • easily switch between different versions of Corona without the need to manually copy the plugin files into the appropriate 3ds Max installation directories or re-installing Corona

    or

  • run two or more instances of 3ds Max at the same time, each with a different Corona version


Currently, it is not possible to have two or more versions of Corona installed on the same computer for the same 3ds Max version when using our universal installer. But there is a way to overcome this using an environment variable method explained below, which we call "using multiloaders". 


Note: the method explained in this guide does not allow you to launch 3ds Max once and then select different versions of Corona from the render engines dropdown inside a single 3ds Max instance. This is currently not possible. 




Introduction


Starting with Corona Renderer 6, the files CoronaMax20XX.dlr and CoronaMaxUtils20XX.dlt installed by our universal installer into the 3ds Max Plugins folder are not actually Corona Renderer plugins. They are just loading the actual plugin files from another directory.

The actual plugin files are installed into %programfiles%\Corona when using the standard installation method, for example: 

C:\Program Files\Corona\Corona Renderer for 3ds Max\2021\Corona_Release.dll


You can use the instructions in this guide to override this default path to a user-specified one. This way, you can decide which specific files to load when starting 3ds Max (e.g. Corona Renderer 6 plugin files or Corona Renderer 7 plugin files). 




Step-by-step instructions


To run a different version of Corona Renderer than the currently installed one:



Step 1 - Install Corona Renderer


Download and install the newest version of Corona Renderer using the standard installation method in our universal installer. It has to be at least Corona Renderer 6 (the oldest supported version is 31.01.2020 daily build).



Step 2 - Download and unpack the other Corona version(s)


Download the additional versions of Corona Renderer you would like to use (they can be stable versions or daily builds, the oldest supported version is Corona Renderer 5).

Use the "Unpack files" option in the installers of each of the additional Corona versions you would like to use.
Unpack the plugin files into any desired folders - see: How to install Corona Renderer manually using the "unpack files" option?



Step 3 - Set up the environment variable


The name of the variable is: 


CORONA_3DSMAX_<YEAR>_LOAD_PATH 


and it should be set to the sub-directory where CoronaMax_Release-<YEAR>.dll file is located after the unpacking. 

For example, for Corona Renderer for 3ds Max 2019 and "C:\Corona Renderer" unpacking directory, set:

CORONA_3DSMAX_2019_LOAD_PATH

to

C:\Corona Renderer\Corona\Corona Renderer for 3ds Max\2019


Here is an example Batch command which does that and starts 3ds Max: 


SET "CORONA_3DSMAX_2019_LOAD_PATH=C:\Corona Renderer\Corona\Corona Renderer for 3ds Max\2019" & START "" "%ProgramFiles%\Autodesk\3ds Max 2019\3dsmax.exe"



Note: the environment variable method set by a Batch command only works for the current session. This means that:

  • If you start 3ds Max normally (e.g. using the 3ds Max desktop shortcut), the currently installed version of Corona Renderer will be used (the one installed using our universal installer). 
  • It is safe to change the environment variable while 3ds Max is running. 
  • It cannot be used to change the Corona version used in the currently running 3ds Max.
  • It allows you to have multiple sessions of the same or different 3ds Max versions running with the same or different Corona Renderer versions at the same time. 


It is also possible to set the environment variable permanently using the options available in Windows 10: simply open the Start Menu and type "environment", then select "Edit the system environment variables". 


You can unpack as many versions of Corona Renderer as you wish and you can select the one you currently need using the method described above. 

To revert to the version which is currently installed using our universal installer, unset the custom environment variable (if it was set permanently), or just launch 3ds Max normally (if it was set for the current session only). 

When using different versions of 3ds Max and Corona Renderer, keep in mind that:

  • Opening scene files saved with a newer version of Corona Renderer using an older version of Corona Renderer is not supported and the file either will not open at all or will open with various issues (e.g. some features not working, incorrect values, etc).

  • It is not possible to open scene files saved with a newer version of 3ds Max using an older version of 3ds Max (the solution is to re-save the scene in an older 3ds Max format in the File > Save as dialog).

  • Opening scene files saved with an older version of Corona using a newer version of Corona is fine. We sometimes enable legacy switches to keep rendering the same between different Corona versions, so if you would like to try new features, you may need to enable them manually in the newer version of Corona.




Corona Renderer 6 and older, Converter Script, and Proxy Exporter    


If you wish to install Corona Renderer 7 or newer and launch Corona Renderer 6 or older using the methods described in this article you may encounter issues with the Corona Converter and Corona Proxy Exporter scripts. This is because the installation path for these scripts was changed.


To solve this issue and be able to use the scripts it is necessary to manually copy the Corona Converter and Corona Proxy Exporter scripts from the directories where they were unpacked to C:/Program Files/Autodesk/3ds Max <version>/scripts/CoronaRenderer/


The above is not necessary in cases of:

  • Running different versions of Corona Renderer 7 using the environment variable method (e.g. the final release and a daily build). 
  • Having Corona Renderer 6 installed using the usual way (through the universal installer) and running Corona Renderer 7 using the environment variable method.
  • Having Corona Renderer 7 or newer installed using the usual way and using the environment variable method to run a different version of Corona Renderer 7 or newer.

Another solution is simply locating the currently needed Corona Converter and Corona Proxy Exporter scripts and manually launching them in 3ds Max, however this is bound to cause some issues such as the Corona Converter button in the Corona Toolbar not working.