Linear Workflow – All you need to know
For those of you embarking on photorealism/physically accurate lighting solutions in maya with mental ray, I did all the googling for you.
Linear workflow means having all our color data confined to the 16bit or 32bit linear color space so that images can continue to have high dynamic range throughout production and post.
Therefore, all textures and maps should be linear sRGB when we work. We should batch render linear formats, and only after compositing should we render out the final 8bit sRGB images we need for broadcast.
Quoting digital tutors:
1. Leave the Color Management settings at default (Default Input Profile = sRGB , Default Output Profile = Linear sRGB)
2. The Color Profile for any diffuse texture maps can be left at “Use Default Input Profile” (which, in this case, is sRGB)
3. Any bump, displacement, specular, transparency maps should have their Color Profiles manually set to “Linear sRGB”
4. When you render, the image will look dark on your monitor.
5. In the Render View, go to Display > Color Management
6. Set the “Image Color Profile” to Linear sRGB, and set the “Display Color Profile” to sRGB
With Method #1, the Default Output Profile (from the Render Settings), and the Image Color Profile (from the Render View in step #5) are both set to Linear sRGB. So Maya is applying a gamma-correction to the entire Render View, making the render look right on your monitor (although it is strictly for preview purposes).
Method #1 is the “approved” workflow described in the Maya documentation…
As a matter of personal preference, though, I don’t like going through the additional step of using the Render View Color Manager. So in “Linear Workflow Rendering Strategies in Maya 2012”, I demonstrate the method that I like to use:
1. In the Render Settings, set the Default Input Profile to Linear sRGB, and the Default Output Profile to sRGB.
2. Manually set any diffuse textures to use a Color Profile of sRGB
3. Any bump, displace, specular, transparency maps can have their Color Profiles left at “Use Default Input Profile” (which, in this case, is Linear sRGB)
4. Hit “Render”. Everything looks great.
In method #2, the key is to have your Default Output Profile set to sRGB. This lets the render be displayed properly in the Render View without any additional adjustments required. However, if you intend to render your final image as a 32-bit (.EXR or .HDR), then you want to make certain you set the Default Output Profile back to Linear sRGB before Batch Rendering (otherwise, your 32-bit images will be washed-out).
I hope this will help you in your renders. For those dealing with physical sun and sky, bear in mind that there is a lens shader attached to the camera by default that has gamma 2.2. Be sure to turn it back to 1 when batch rendering.
I also come across the problem of rendering a black background for the sun and sky. Don’t be deceived as this is a linear output. It will show up when you import into Nuke. If you don’t have a compositing package like Nuke, consider rendering the background in sRGB 8bit as a separate layer.