Use the OS Normal Pass to Change the Lighting in Composition
If you have ever used the ZBrush to Photoshop plugin to export your render passes you will realize that one of them is the Object Space Normal or OS Normal pass. In case you haven't, the plugin is already installed on ZBrush by default and it is located in the ZPlugin menu. Learn more about how I create awesome renders in ZBrush.
This tutorial, however, is about using the OS Normal pass to create new lighting sources on the composition side in a non-destructive way. Learn how to have more control over the lights when you are compositing by following this guide.
Creating the Lighting Setup
To start with the process, you will need to ensure you have the adjustment layers panel visible on Photoshop:
- Navigate to Window > Adjustments. Ensure it is checked.
Once you have located the adjustments panel add the next 4 adjustment layers above the OS Normal layer pass in the same order:
- Hue saturation
- Channel Mixer
- Hue saturation
This adjustment layers only has to effect the OS Normal layer pass, so you will make them act as a clipping mask, do it by clicking between layers while holding the left Alt button on your keyboard.
Tweaking the Light Hardness
Select the Levels adjustment layer and raise the mid-tone slider to separate better the RGB (Red, Green, Blue) channels.
In the Channel Mixer tick the monochrome checkbox to turn the image into a greyscale, the resulting image represents your new light. You can tweak the sliders to make the light harder or softer, to make it harder just rise one slider and lower the other two.
Change the Lighting Angle
Go to the second Hue Saturation and move the Hue slider to change the direction of the light, move this around till you get the lighting angle that works best for your scene. Once you're satisfied with the lighting, change the OS Normal layer blending mode from Normal to Screen and adjust the layer opacity to integrate with the other elements of your compo.
Tint the Light
Here is when the magic does its effect, on the first Hue saturation, you can turn on the colorize checkbox to tint your light, then the only you have to do is adjust the Hue and Saturation sliders. Move the hue slider to oranges or reds for a calid feeling, otherwise if you want it to have cooler tones move the slider to blues and purples.
In fact, normally is a combination of both, calid tones on the main light and cold tones on the secondary one. Talking about the secondary lights...
Create Multiple Lights
Finally, put all the adjustment layers you have created together with the OS Normal pass inside a new folder. There you go, you have just created your first lighting setup.
Now if you want to create a secondary light source just duplicate this setup and adjust the angle.
This is a very useful way to generate lighting sources on the composition side. Obviously is not ideal because the resulting light will not be as realistic as a rendered one, but at the end of the day it makes the function and can save your ass in multiple situations.
I also attach a video from Danny Mac which will help you to complement the understanding of this process.
If you have any questions, suggestions, or have a different method that you wish to share to us, let me know in the comments below.