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Linear vs Exponential Workflow with 3Ds Max and VRay

Color Mapping in VRay

Note: This entire tutorial is going to revolve around the concept of Display Gamma. In order to get a better grasp of this subject, I’d suggest you read this brilliant article. This will give you an in-depth understanding of Gamma Correction and why it’s used.

Regardless, let me give you a brief overview of what Gamma is. Gamma is essentially a Curves adjustment applied to an image, just like you would in Photoshop. All lossy photograph formats have a standard gamma value of 2.2 applied to them by the camera itself. To make sure the image looks the same on a display, the monitor applies an inverse of this value before displaying.

Especially relevant, this process occurs only for lower bitrate image formats like jpegs or pngs. The reason behind this is to avoid compression artifacts in the shadows.

The idea behind applying a gamma of 2.2 within 3ds Max is to replicate the same process for your virtual photographs. This is what is known as a Linear Workflow. Interestingly, 3ds Max and VRay are now both configured for Linear Workflow by default.

Note: Do not use the ‘Linear Workflow’ option in VRay Color Mapping settings. It is a deprecated option and not the correct way of getting a linear workflow.

You can check this by going to the Rendering Main Menu > Gamma/LUT Setup. ‘Enable Gamma/LUT Correction’ should be ticked and the Gamma value should set to 2.2. Affect Material and Color should also be ticked. As of ver. 2014 of 3ds Max, Input and Output Gamma options for files are hidden. These values are also set to 2.2 by default. This means that input textures will be considered to already have a gamma of 2.2 and output files will be burned with 2.2 as well.

In case any of your textures looks darker after import, you may need to override import gamma to 1. Usually all pictures and textures are encoded with the standard 2.2 gamma.

The only exception to this rule are high bitrate image formats like EXR or HDR. These formats don’t need any gamma correction and are supposed to be displayed by the OS with gamma 1. Finally, with a Linear Workflow setup we can focus on 2 color mapping workflows. The color mapping options are provided by VRay in its main render settings.

Linear Color Mapping

This method of workflow involves setting color mapping to ‘Linear Multiply’. Set the gamma value underneath it to 1.0 and unclamp the colors. The mode will be ‘Color mapping and gamma’. You will also need to enable the sRGB color space in the VRay Frame Buffer. This will allow you to view the image with gamma 2.2 in the frame buffer.

Finally, you need to save it as an EXR or HDR file. Therefore this will retain all the color data for every pixel. This format is best used when working with compositing applications like NUKE, After Effects etc.

Exponential Color Mapping

As the name suggests, the color mapping mode is set to exponential and gamma to 2.2. Also, for this workflow you won’t need to set the color space to sRGB in the VFB. This method is more like Fake Linear but easier to work with. In this mapping mode, the details in the brightest and darkest pixels are compressed into the image.

You can directly save it out as PNG or TIFF with an output gamma override of 1.

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