How to use Interactive Rendering in Corona for Cinema 4D?

Enabling Interactive Rendering

To enable IR, click on the "Start Interactive Rendering" button in the Corona VFB:

While you can start the IR from either the Corona VFB or the Corona menu, once it is running, the native Cinema 4D Picture Viewer will update in sync with the VFB.

What can you do while IR is running?

Once IR is running, you can:

• Add, edit, move, or delete objects and lights
• Edit or apply materials
• Change post-processing settings (in the Corona VFB or in the Picture Viewer post-processing dialog)
• View Depth of Field
• View stats (Such as Denoise amount, Pass amount, Estimated rendering time, etc.)
• Render history (View comparisons between renders, save previous renders to disk)
• LightMix (Edit and fine-tune your lighting setup in real-time)
• Upload your images to the Chaos Cloud Collab

Focusing processing power on particular areas in the image during IR

Sometimes, you will want to focus on a particular area of an image and do not need the whole image to update. This can be done in one of two ways:

Zoom in on the image in the Corona VFB

When you zoom in on the image in the Corona VFB (mouse scroll wheel or the zoom-in icon), only the area currently shown in the Corona VFB will be processed. This will make that area clean up faster, while the rest of the image remains "on pause". As soon as you zoom out, processing will resume on the rest of the image.

Note that this ONLY applies to Interactive Rendering - you can zoom in and out during a full render, and the whole image will continue to be processed.

Use Render Regions in the Corona VFB

You can add as many Render Regions as you like in the Corona VFB. When one or more Render Regions are added, only those areas of the image will be processed, and by focusing the processing on those areas, they will clean up faster. While the VFB is running, you can add, move, resize, and delete Render Regions.

Optimizing performance while IR is running

Limit the number of cores used for IR

By default, IR uses "all your cores -1" which leaves one core free to handle anything else you may be doing on the machine at the time. You can change this to 0, to use all available cores during IR and give greater IR performance (at the expense of some system responsiveness), or lower it to -2, -3, etc. to reduce the cores used and give greater system responsiveness (at the expense of IR performance).

You can adjust this under Preferences > Corona > Interactive Rendering section as shown below:

Limit the Max Number of passes for IR

This lets you have IR stop after a certain number of passes have run. When set to 0, IR will run indefinitely - for any other value, IR will stop when that number of passes is reached, useful when you only need a limited preview quality during IR. You can change this value while IR is running (but it will always restart the render from 0 passes if you do change the value). This setting has no effect on final renders.

Force path tracing

By enabling this option, you force IR to use path tracing rather than the UHD Cache, no matter which solution is set for the final render. This can improve the start-up performance of IR, as the UHD Cache will not need to be calculated. This setting will have no effect on your final render.

Denoising during Interactive Rendering

In Corona 10 and newer versions, denoising during Interactive Rendering can be toggled from
Render Settings > Corona > Performance settings > Interactive Rendering > Fast Preview denoise during render. This will use NVIDIA GPU AI denoiser (also called "Optix") to denoise the render.

In Corona 11, Intel CPU / GPU AI denoiser (more accurate but slower) was added as an option for interactive denoising. Starting from Corona 11, the preferred interactive denoiser can be selected in a roll-down menu at the same place:

Note:  In Corona 11, the Intel AI denoiser is supported only by Windows-based systems and its GPU mode only works on NVIDIA GPUs. 

Learn more about the different types of denoisers here.

Using IR Subsampling for Faster Interactive Rendering

IR Subsampling can help you optimize the interactive rendering speed. Values higher than 0 render the image in a lower resolution for the first few passes. This makes interactive rendering faster and more responsive, but also "pixelated" for a few seconds, until more passes are added. This helps you see the changes you make to your scene faster, so you can make decisions and adjustments more quickly.

This feature helps maintain a consistent resolution during interactive rendering in Corona VFB, making it easier to see changes in your scene without the resolution adjusting automatically.

Related articles: 

• How to use Interactive Viewport Rendering in Cinema 4D?

See also: Corona Interactive Rendering at the Chaos Documentation Portal.