Automation and change host UI parameters from Plugin

Hello to the VST3 dev community,

I have a question about the automation and the possibility of a VST3 plugin to write automation in the DAW host.
Is there a way to make changes of the Host GUI (such as a gain slider) from the plugin and therefore, write these changes in automation ?
The idea is that the plugin make changes of parameters in the host UI such as the user would do and those changes are written fr automation ?

Thanks for your support.


not sure to undestand 100%, but a host could have a UI Knob (or a remote physical fader) connected to a plug-in parameter (like in Cubase with the QuickControl), when the user moves it, the information could be written into an automation, the controller (and the plugin-UI) gets the changes with ->setParamNormalized…and the processor gets the changes too in the process call.

Thank you for this clear answer.

But my question may be too long or not well defined. A short version of my question is :

Could a VST plugin write automation in the Host UI Daw ?

The VST plugin read a wave file data and depending on a fixed target value for one parameter (ex : a target value for the Gain parameter) , the VTS plugin writes the automation in the DAW to match the target value. This VST plugin could process itself the Gain stagging automation on a track or a bus.

Thanks for your support.

A VST Plugin could only write automation during playback at the current position where the plugin send a performEdit to the host…
Some hosts support writing of automation for parameters sent back (outputParameterChanges) in the process call.

I understand now. Is Cubase 12 able to do such a writing automation of parameter sent back in the process call ?
Thank you for sharing your knowledge.