This is a legacy documentation space! Please refer to V-Ray Next for Maya help for most up-to-date information.

This page provides information on the Color Corrections dialog in the V-Ray Frame Buffer.

 

Page Contents

 

Overview


The V-Ray frame buffer enables various color corrections to be applied to the image. Some of the corrections are applied only when the image is displayed on the screen, but are not applied when the image is saved to disk. Corrections that are not applied for disk images are those that are only required to display the image - i.e. sRGB, LUT, OCIO, ICC color corrections. Corrections are generally applied as they are listed in the color corrections window from top to bottom - i.e. exposure is applied first and display color corrections like LUT, OCIO and ICC are applied last.

To show the Color Corrections dialog, click the Show corrections control button in the VFB Toolbar. Enable color correction elements by pressing the check box to the left of its name. Expand and hide the parameters for a particular color correction using the button. Press the button displays a short menu that allow you to reset the parameters for the particular color correction to their default values, and to save and load just the parameters for that color correction.

The Color Corrections panel can be docked or undocked from the VFB by right-clicking the Show corrections control button.

 

 


 

UI Path: ||V-RayFrame Buffer window|| > VFB Toolbar > Show corrections control button

 

 

 

Global Presets


 

 

 

Clicking on the Globals... button shows a menu for saving and loading all color correction attributes.  

There are two filters for files to save.

LUT (*.cube) – Saves a LUT that can be used to load all vfb color corrections into composting packages such as Nuke.
Global Color Correction file (*.vccglb) 
– Saves a file that stores all the VFB color correction info to load into the VFB.

 

Exposure





Applies exposure and contrast to the image. Exposure of 0.0 leaves the original image brightness, +1.0 makes it twice as bright, -1.0 makes it twice as dark, and so on. Highlight Burn allows you to selectively apply exposure corrections to highlights in the image. Positive Contrast values push the colors away from the medium gray value to increase image contrast, while negative values push the colors closer to medium grey.


White Balance





Sets the white balance to correct the temperature of the image so that objects that are white appear white in the final image.


Hue/Saturation


 

 

 

Applies HSL transformation on the image colors. Moving the Hue slider changes the overall hue of the image colors (grey colors remain intact). Lower Saturation values move the image towards greyscale while higher values increase the colors. Higher Lightness values add white to the image, whereas lower values subtract white from the image.

 

Color Balance


 

 

 

Adjusts the overall color tone of the image, as well as the tone of the dark (shadow), medium and bright (highlight) colors. The color corrections are additive in that the All correction affects all colors of the image, and the Shadows/Midtones/Highlights corrections adjust the individual components on top of the All correction.

 

 

Levels


 

 

 

Displays a histogram of the image colors and remap sliders. The buttons allow you to view the distribution of the individual color components only, and the turns on all three components.

Move the two slider nodes below the histogram to remap the image colors. Ctrl+left click below the gradient between two sliders to add a new slider between them. Shift+click on a slider to delete it.

 

 

Curve


 

 

 

This correction allows you remap the image colors with a Bezier curve. The control also allows you to save and load .acv curve files from Adobe PhotoShop.

Controlling the View

Use the mouse wheel to zoom in and out of the curve view. Drag with the middle mouse button to pan.

Controlling the Bezier Points

Click on a point to select it. Draw a rectangle to select multiple points at once. Click and drag on a selected point or its tangents to move them. To add a new point, Ctrl+click on the curve. To delete points, select them and press Del, or alternatively Shift+click on a point. Once a point is selected, you can also use the input coordinates field in the upper left to modify its position.

Right-click on a point to bring up a context menu with additional options for that point:

 

 

Context Menu

Right-clicking in the curve view brings up a context menu with additional options:

 

 

 

The following menu items are available:

Menu itemDescription
Zoom allAdjust the curve view so that all points are visible
Undo/RedoUndo and redo modifications to the curve
LoadLoad the curve control from a file. Two formats are available: native .bcurve and PhotoShop .acv.
SaveSave the curve control to a file. Two formats are available: native .bcurve and PhotoShop .acv
ResetReset the curve control to its default state.
Select internal onlySelect only the points which are currently visible in the curve view.
Select allSelect all points.
Snap to gridToggle snapping to the curve grid. When enabled, moving points snaps them to the grid nodes.

 

Note that when working with .acv files, some approximations are performed, as the curves in the .acv files are described by a different mathematical formula.

 

Background Image





Loads an image to use as a background for your rendering.

Load – Select a file that is going to be used as a background

Clear – clears the loaded file

As foreground – when enabled the image loaded in the field above will be used as a foreground. This means that the image will be on top of the rendering and you will be able to see the rendering only if the image has an alpha channel.


LUT


 

 

 

This correction allows you to remap the image colors based on an IRIDAS .cube LUT (Look-Up Table) file. This is a display correction that is only applied when the image is viewed in the frame buffer. It is not applied when the image is saved to a file.

This correction can be controlled with environment variables. Settings VRAY_VFB_LUT=1 automatically turns on the LUT correction by default. A LUT file can be specified with the VRAY_VFB_LUT_FILE environment variable.

 

OpenColorIO (OCIO)


 

 

 

Applies display color corrections from an .ocio color profile to the image colors. When enabled and no specific .ocio profile is specified, it will attempt to read the OCIO environment variable and apply the profile specified in it. This is a display correction that is only applied when the image is viewed in the frame buffer. It is not applied when the image is saved to a file.

This correction can be controlled with environment variables. Settings VRAY_VFB_OCIO=1 automatically turns on the OCIO correction by default.

Input color space – Choose the input color space for the image; normally this is a linear color space as V-Ray internally works in that space.

Display device – Choose the device on which the VFB with the image is displayed.

View transform – Specify the viewing transformation.

 

ICC


 

 

 

Applies an ICC profile to the image so that it matches f.e. the appearance of the image in Adobe PhotoShop. This is a display correction that is only applied when the image is viewed in the frame buffer. It is not applied when the image is saved to a file.

This correction can be controlled with environment variables. Setting the VRAY_VFB_ICC_FILE allows to automatically specify an ICC profile.