This page provides an overview of the V-Ray Frame Buffer.



In addition to rendering to the Houdini® Render View, V-Ray has a V-Ray specific frame buffer, which has some additional capabilities:

  • View all render elements in a single window and switch between them easily
  • Keeps the image in full 32-bit floating point format
  • Perform simple color corrections on the rendered image
  • Choose the order in which the buckets are rendered
  • Store a list of recently rendered images and switch between them easily
  • Apply lens effects to the rendered image


When using the V-Ray Renderer, the Frame Buffer settings are set to their defaults. This launches the VFB whenever a production render or IPR render starts.


UI Path

||V-Ray Shelf|| > Show VFB button


VFB Toolbar


This dropdown gives access to render elements rendered for the scene. The selected render element is displayed in the VFB. By default, the RGB color and Alpha render elements are available. Any additional render elements that have been added to the scene also appear in the dropdown.

This part of the toolbar sets the currently selected channel, as well as the preview mode. Choose which channels to see with the help of the buttons. You can also view the rendered image in monochromatic mode.

The RGB Button switches the current channel to RGB color by default. When effects are applied, such as the VRayDenoiser or Lens Effects, the button toggles between the effectsResult channel and RGB color channel.

Saves the image into a single file. If a multi-channel type file is used (.exr, .vrimg) all the render elements are saved in the same file.
Saves all the render elements into separate files.

Saves all image channels to a single file. If a multi-channel type file is used (.exr, .vrimg) all the render elements are saved in the same file. (available from flyout).

Opens an image file to be previewed in the V-Ray Frame Buffer.

Copies the current channel to the clipboard.
Clears the contents of the frame buffer. Sometimes helpful when starting a new render to prevent confusion with the previous image.
Copies the current V-Ray frame buffer to the Houdini Render View.
Forces V-Ray to render the closest bucket found to the mouse pointer. Drag the mouse over the V-Ray frame buffer while rendering to see which buckets are rendered first. You can turn this on and off on-the-fly while rendering.
Allows you to render regions in the V-Ray VFB.
Links the V-Ray VFB to Pdplayer.
Stops the current rendering.
Repeats the last render. Right-click button to access a list of available cameras to render from.
Opens the Color Corrections dialog which lets you define color corrections of various color channels.
Forces color clamping in the V-Ray VFB. Click and hold left mouse button to display the clamped colors in the V-Ray VFB.
Permanently opens the info dialog which gives you information about the pixel you right-click the mouse pointer on. If you right-click the mouse pointer over a pixel without turning this setting on, you see the info dialog only while your mouse button is down.
Enables the Hue/Saturation/Lightness color corrections.
Enables the color balance corrections.
Enables the levels color corrections.
Enables the curve color corrections.

Enables the exposure corrections.

Enables the usage of a background image.
Displays the image in sRGB color space. Click and hold the left mouse button to switch between sRGB color space and ICC.
Enables and disables the effect of the Look Up table loaded in the Color Corrections settings. Hold down to chose between LUT and OCIO color corrections.
Shows the V-Ray VFB history window.
Enables visualization of the pixel aspect ratio.
Enables or disables stereoscopic preview. Click and hold down the left mouse button to pick between several stereoscopic modes
Opens forth the Lens Effects controls



If an 8-bit file is saved through the VFB or the Render Output / Save image settings, the sRGB gamma curve is embedded and the image appears as in the frame buffer when loaded in an external image viewer. If a 32-bit (exr, hdr, tif) image is saved, it remains linear and relies on the external image viewer to handle the gamma.

Color Corrections

The V-Ray VFB has a robust Color Corrections control (as seen in the image in the Overview) that is enabled with its icon (shown in the table above) which is in the lower left corner of the VFB window. Color Corrections include Exposure, Hue/Saturation, Curves, etc. and are all covered here.


Render History

The V-Ray VFB keeps a history of previously rendered images, and lists each with a number, thumbnail, and textual details in the Render history. This history can be accessed through the H icon at the bottom of the VFB window. The Render history can be docked to the VFB (as shown below) or can float separately. In addition to keeping history, this feature can display two images in the VFB for comparison (as shown below), which is revealed via a sliding division line. History files are stored as .vrimg files in a user-specified folder.


VFB with docked Render history, comparing A and B images with vertical division line


Enables the V-Ray VFB history
Saves the current image from the VFB to the render history
Loads the image selected in the Render history to the VFB
Removes the selected image from the render history
Sets the currently selected image as image A for A/B comparison in the VFB
Sets the currently selected image as image B for A/B comparison in the VFB

Swaps the A and B images.

Enables or disables the image comparison. Click and hold the button to switch between horizontal and vertical comparison.
Opens out the Render History Settings window.


The keyboard keys from 1 to 9 are used to quickly switch between the first 9 images from the history.


Right-clicking on an image in the VFB history brings up a pop-up menu with some useful options.

Image Info window


Edit comment
 – Adds a text comment to the image; the comment appears in the "Details" column.

Set A – Sets the image as the 'A' image when comparing two images;

Set B – Sets the image as the 'B' image when comparing two images;

Load – Loads the selected image in the VFB (same as double-clicking on the history image);

Delete – Deletes the selected image from the history.

Load V-Ray Settings – Applies the V-Ray Render settings stored in the stored image. 

Compare V-Ray Settings – Opens a comparison window that displays any differences in the current render setting with the saved ones.

Image Info – Opens a window containing detailed information about the image, including, but not limited to Camera, Aperture, FOV, Target Distance, V-Ray version, and render time. Have in mind that the camera values are saved in system units. Also, the vrayrevison info displayed in the list is not related to the saved .vrimg file but to the current V-Ray build installed for Houdini.

Manually saved .vrimg files can also be added to the History folder, but they need to be saved with all image channels in one .vrimg file to keep the complete image info.

Load Color Corrections – Loads the Color corrections saved in the stored image.

Reload History – Updates the Render History with the current .vrimgs in the VFB history folder.


Render History Settings

This window allows the user to specify VFB History settings such as the location where the history is saved and the amount of disk space to use.

History Directory – Specifies the location where render history images are saved as V-Ray Image files (.vrimg).

Maximum Size on Disk (MB) – Specifies the max amount of disk space to use for the render history images. When the history exceeds the specified amount, the oldest images are deleted.

Use Project Path – When enabled, creates a new vfb_history folder to use as the History Directory within the current Houdini project directory.

Auto Save – When enabled, all rendered images are automatically saved to the history.

Completed Renders Only – When enabled, only completed rendered images are automatically saved to the history.

Auto Load Color Corrections – When enabled, color corrections saved in the stored image are automatically loaded into the Color Corrections panel.

Clear – Clears all images in the render history.

Resize VFB on Load Image – When enabled, the VFB is automatically resized to fit the loaded image.


Stamp Tools




Toggles open Stamp Tools at the bottom of the VFB
Applies a stamp with rendering metadata to the image
Opens the Stamp Variables window to make it easy to copy different types of information onto the stamp
Align stamp options; Click and hold to change from Left alignment to Right alignment or Center alignment
Changes stamp placement from align Bottom to align Top
Choose Font window to change font, its style and size


Stamp Variables

Stamp variables can be typed directly into the stamp textbox with a % symbol before and separated with a | symbol. Example: %rendertime | %frame | %camera

Alternatively, the Stamp variable window can be used to select/highlight variables and clip on the Copy to stamp button to add them to the stamp textbox



vraycoreVersion of the V-Ray core
rendertimeThe render time for the last completed frame
vrayversionInternal V-Ray version
filenameHoudini project file name
primitivesNumber of internal V-Ray primitives used in rendering
computernameThe name of the computer this frame was rendered on
dateDate at the end of rendering
timeTime at the end of rendering
ramPhysical memory available (RAM)
vmemVirtual memory available
mhzThe speed in Mhz of the CPUs
cpuCPU type and number of CPUs available
osOS version
cameraCamera name
numPassesSampling level reached: number of passes
numSubdivsSampling level reached: number of subdivs



VFB Shortcuts

Here is the list of shortcuts to navigate through the VFB image. Please note that VFB window must have the current focus for the shortcuts to have effect:


CTRL+Left click, CTRL+Right clickZoom in/Zoom out
Mouse wheelZoom in/Zoom out
Double-click left buttonZoom to 100%
Right click

Show the info dialog with the properties of the last pixel clicked. In order to see the info non-stop - turn on the info dialog button 

Page Up/Page DownSwitch between render elements
Middle button draggingPan (hand tool)
+ / -Zoom in/Zoom out
*Zoom to 100%
Arrow keysPan left, up, right, down
1-9Load the respective image from the VFB history
Ctrl+CCopy the VFB image to the Windows clipboard; the image is copied exactly as it appears on the screen (meaning sRGB/LUT/OCIO etc corrections are applied). The full resolution image is copied to the clipboard, even if the VFB view is zoomed in/out.

Changing the Background Color

To change the background color of the VFB, right-click on the background and select one of the options from the pop-up menu.


Pixel info
 – Left-click at any point of the rendered image to open the standard V-Ray VFB pixel information window. Hold the left mouse button and move the mouse around to check each pixel's info.


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