This is the first of two tutorials in which I will examine two aspects of the rendered image that I am currently showing on screen: how to create volumetric lights when the scene's light source is Nishita Sky, and which Compositing nodes to use to get the final result.
Video Transcript
Hello everyone! This is the first of two tutorials in which I will examine two aspects of the rendered image that I am currently showing on screen: how to create volumetric lights when the scene's light source is Nishita Sky, and which Compositing nodes to use to get the final result.
The tutorial was created with Blender 3.6, and, like most of my tutorials, its text version is available for free download at the link provided in the description.
The scene used for rendering is a simple classroom, which I assembled using some of my assets within the room. The lighting is provided by the virtual universe only, particularly using Nishita Sky, so there are no other light sources in the scene.
Starting the rendering in Cycles with Denoise enabled, this is the result we get: nice, but adding volumetric light and some Compositing would certainly make the atmosphere more interesting.
To add a volumetric light effect to a scene, you can use the Volume Scatter node from the Shader group, which provides a Volume-type output that can be connected to the Volume input of the World Output node or another Shader node.
The problem that arises when directly connecting Volume Scatter to the Volume input of the World Output node is that the resulting image is completely black.
This is because the node considers the light scattering given by the entire World volume, which is virtually infinite in size, so the light cannot pass through, even if we greatly reduce the value of the Density parameter of the node.
For this reason, it's often common to insert a cube or another solid object into the scene and apply Volume Scatter to this volume. However, I didn't want to resort to this solution because I wanted to find a way to apply Volume Scatter directly to World Output.
To solve this problem, I inserted a Light Path node into the editor, specifically taking the is Camera Ray output and using it as a mixing factor in a Mix Shader node to decide whether to use the Volume Scatter node or not.
The reasoning behind this is as follows: apply Volume Scatter only to the portions of the scene directly framed by the camera, ignoring the rest.
This will nullify the light absorption in the rest of the virtual environment, allowing light to pass through and undergo attenuation only in the final portion.
The result, obtained by slightly lowering the density and using the World lighting as the color of the Volume Scatter node, is the one you can see right now.
To achieve the rendering I showed you at the beginning of the tutorial, it's necessary to set up some nodes in Post-Production, but I will talk about this in the next video! See you soon!