How to Fix: Cannot see Corona VFB when Rendering

Corona VFB Not Appearing During Renders

The Corona Frame Buffer (VFB) is one of Corona Renderer's most powerful tools. It provides real-time render feedback, interactive tone mapping, denoising, and pass management. When the VFB window fails to appear during rendering, you lose access to these critical post-production controls — and your render becomes harder to monitor and adjust.

We've helped thousands of artists troubleshoot missing VFB windows at Super Renders Farm. Whether you're submitting work to our render nodes or rendering locally, the VFB must display correctly for your pipeline to work smoothly.

Why Your Corona VFB Isn't Showing

The Corona VFB window relies on two primary settings working in harmony. For additional troubleshooting resources, see the official Corona Renderer documentation.

1. Rendered Frame Window toggle — This controls whether ANY render output window displays at all
2. Frame Buffer Type setting — This specifies which type of buffer displays (VFB vs standard window)

If either setting is misconfigured, the VFB either won't spawn or will be replaced by a basic render window. The issue is common in early Corona 1.x versions but can occur across all current versions (Corona 4-5) if settings get corrupted or reset during scene imports.

Solution: Verify Rendered Frame Window Setting

Step 1: Open Your 3ds Max Render Setup

1. In 3ds Max, go to Render > Render Setup (or press F10)
2. Navigate to the Common tab
3. Locate the Render Output section at the bottom of the panel

Step 2: Enable Rendered Frame Window

Look for the checkbox labeled "Rendered Frame Window" (or sometimes "Display in Viewport" depending on your 3ds Max version). This checkbox must be enabled (checked).

If this box is unchecked, Corona won't open any rendering window at all. Check this box and try rendering again.

Screenshot reference: Look for the toggle in the Common Parameters area of Render Setup.

Solution: Configure Frame Buffer Type

Once the Rendered Frame Window is enabled, you need to specify that you want the Corona VFB, not the default 3ds Max buffer.

Step 1: Access Frame Buffer Settings

1. In Render Setup, go to the System tab
2. Expand the Frame Buffer section
3. Click on VFB Settings

Step 2: Set Type to Active VFB

In VFB Settings, locate the Type dropdown. Your options are typically:

• None — No buffer window (renders to memory only)
• Classic VFB — Corona's legacy interactive buffer (1.x-2.x)
• VFB 2.0+ — Corona's current interactive buffer (3.x-5.x) — SELECT THIS
• Corona Picture Viewer — External image viewer

Do NOT select "None". This is the most common mistake. Select the Corona VFB option appropriate for your Corona version:

• Corona 1.x–2.x: Select Classic VFB
• Corona 3.x–5.x: Select VFB 2.0+ (recommended)

Once changed, try rendering again. The VFB window should appear within seconds.

Frame Buffer Version Differences

Corona has two active VFB implementations:

Corona Classic VFB (1.x-2.x)

The original interactive frame buffer. Features include:

• Real-time render feedback and progress
• Basic tone mapping and exposure adjustment
• Pass management and LUT application
• Supported on Corona 1.x and 2.x

If you're using an older Corona version, this is your standard choice.

Corona VFB 2.0+ (3.x-5.x)

The modern frame buffer introduced in Corona 3. Major improvements:

• Denoiser integration (OptiX and Intel Open Image Denoise)
• Multi-pass editing and layer-based workflows
• Advanced tone mapping with LUT 3D support
• Watermark control and frame tagging
• Better integration with 3ds Max material preview

For Corona 4 and 5, always use VFB 2.0+. It's more stable and includes crucial denoising tools that speed up your workflow.

Troubleshooting If VFB Still Doesn't Appear

If you've verified both settings and the VFB still won't show:

Common Issues Beyond Settings

1. GPU Driver Conflict — Outdated NVIDIA or AMD drivers can prevent VFB rendering. Update to the latest driver version.

2. Secondary Monitor Problem — Corona VFB sometimes opens on your secondary display (if you have one). Check all connected monitors or disable secondary displays temporarily.

3. Resolution Mismatch — If your render resolution exceeds available screen space, the VFB window might spawn partially offscreen. Try a smaller test resolution (800×600) to verify.

4. Corrupted Scene File — Import the scene into a fresh 3ds Max file. Render setup corruption can prevent VFB initialization.

5. Interactive Rendering Disabled — Some settings disable both standard rendering AND interactive rendering. Verify under Render Setup > System > Interactive Rendering that it's enabled.

Rendering Corona Scenes on Cloud Render Farms

When submitting Corona projects to Super Renders Farm, the VFB settings carry over correctly. However, note that:

For detailed guidance on packaging your 3ds Max scenes for cloud rendering, see our complete packaging guide.

• Cloud render nodes process your scene in headless mode (no display)
• The VFB won't display on the farm — it's only for local preview
• EXR outputs with all passes are saved and downloaded after rendering completes
• Configure your VFB settings locally to match your final output requirements

Before uploading, test your render locally to confirm the VFB displays and tone mapping is correct. Your settings will persist in the .max file and ensure consistent results on the farm.

FAQ

Q: Why does Corona render to a basic window instead of the VFB? A: Your Frame Buffer Type is set to "None" or a non-Corona option. Go to Render Setup > System > Frame Buffer > VFB Settings and change Type to "VFB 2.0+" (Corona 3+) or "Classic VFB" (Corona 1-2).

Q: Can I render without the VFB window? A: Yes, but not recommended. Disable "Rendered Frame Window" in Render Setup > Common to render without any display window. You'll see progress in the 3ds Max status bar only.

Q: Does the VFB affect render speed? A: No. The VFB is purely a display interface. Disabling it won't speed up rendering. Leave it enabled for monitoring and tone mapping.

Q: How do I use the Corona denoiser through the VFB? A: In Corona VFB 2.0+, once rendering completes, go to the Denoiser tab and select your denoiser (OptiX or OIDN). Adjust strength and apply. This happens entirely in the VFB post-render.

Q: What if the VFB opens but shows a black or corrupt image? A: This indicates a GPU driver issue or color space problem. Update your graphics driver, or try disabling GPU acceleration: Render Setup > System > GPU > Disable GPU.

Q: Does the VFB work on cloud render farms like Super Renders Farm? A: No. Cloud nodes render headless (without display). The VFB is strictly a local preview tool. Your render outputs and EXR passes are saved and downloaded after the farm completes processing. Learn more about corona cloud rendering.

Q: How do I properly set up Corona for render farm submission? A: Ensure your Corona scene is properly packaged with all assets. Check our guide on packaging 3ds Max files for render farms for detailed instructions.

Q: How do I save a corona render from the VFB? A: In the Corona VFB, go to File > Save Image or use the save button in the toolbar. You can export to EXR, PNG, JPG, or OpenEXR multilayer formats.