How to use Interactive Rendering?


What is Interactive Rendering?


In Corona, final frame rendering and Interactive Rendering (IR) are handled by the same engine. In fact, final frame rendering is the same as Interactive Rendering, only with scene updates disabled. IR and final rendering shouldn't be visually different, they are both capable of producing the same effects, support the same features and even use the same GI solvers. IR, just like regular VFB rendering, will react to exposure controls in real-time. When rendering, IR gives immediate response, while regular rendering is faster in the long run. Any kind of rendering done in Corona, including IR, is solely CPU-based. 


Interactive Rendering in Corona cannot be enabled using 3ds Max's "Active Shade".




How to use Interactive Rendering?


There are two Interactive Rendering modes in Corona:


1. Docked in viewport:


To enable it, right-click on the name of a viewport of your choice (for example [top], [left] or [perspective]), select Extended Viewports > Corona Interactive.



This will set your current viewport as an Interactive Rendering window. To start rendering, simply left-click anywhere inside that window. You can resize your interactive window's size by resizing the viewport grid. This Interactive Rendering mode can't be stopped or paused.


To disable Interactive Rendering in current viewport, either right-click inside it, or left-click inside it and press "V" key, and then pick another view from the drop-down menu:



Note: you can also left-click inside Interactive Rendering window and press "C" key to copy the content of Interactive Window into 3ds Max VFB - this is useful for example when you want to save the image generated in the Interactive View.



2. Undocked (floating window):


To enable it, go to Render Setup > Scene > General Settings and press the "Start interactive" button. This will open Corona VFB with Interactive Rendering running. To resize it, simply resize the VFB window - Interactive Rendering window is independent from output size specified in render setup. 




To stop rendering, simply close the window or use built-in VFB controls:





Troubleshooting


1. Interactive rendering changes viewing angle each time I pick another viewport!
 

To lock interactive rendering to specified viewport, so that it does not change when you switch to another viewport, go to Render setup and with the viewport of your choice selected, press the small lock button at the very bottom of the window. 





2. IR is rendering black screen only!

This could mean there is no light in your scene. Make sure you have added at least one light source.



3. Interactive rendering does not work!

Please see this guide for a possible solution: I cannot see Corona VFB!



4. How to optimize CPU usage when using interactive renderer?

Interactive rendering utilizes a lot of computing power which may sometimes result in increased heating and CPU fan noise. To reduce these, you can use "# of threads override" and "Max passes" options which are available in Render Setup > Performance > Performance Settings > Interactive rendering.
"# of threads override"
is the number of cores to use for interactive renering. Positive values work in straightforward way. Value of 0 means that all system cores will be used. Negative values will use all cores but the number specified (-1 means all cores but 1).
"Max passes"
limits the number of passes rendered in the interactive mode.