This page gives some basic details about the Raw Reflection render element and how it is used in compositing.
The Raw Reflection Render Element stores reflection information calculated from the materials' reflection values in the scene. Surfaces with no reflection values set in their materials contain no information in the render element, which means these areas render as black. When the Raw Reflection Render Element is multiplied by the, the Reflection Render Element is produced.
Raw Reflection gives the full reflection of objects reflecting in the scene, whereas the Reflection Filter Render Elements sets how much of that reflection should come through in the composite. In other words, the filter defines the strength of the reflection, whereas the raw image defines what is being reflected in the image. When these two elements are multiplied, the true level of reflection is given as the Reflection Render Element. By using these component parts of the reflection, you can fine-tune the reflection in your final composite.
||Shading viewport|| > Shader Tree > Add Layer button > V-Ray Render Elements > V-Ray Additional Outputs > Raw Reflection
This render element is enabled and controlled through the V-Ray Additional Outputs properties.
Enable Raw Reflection – Enables the Render Element.
Name – Sets a custom name for the Raw Reflection Render Element.
Deep Output – Specifies whether to include this Render Element in deep images.
Apply Color Mapping – Applies the color mapping options specified in the Color mapping rollout of the V-Ray Main Render Settings.
Denoise – Denoises the render element.
The Raw Reflection Render Element is useful for changing the appearance of reflective scene elements in compositing or image editing software after the scene is rendered. Below are a couple of examples of its use.
Underlying Compositing Equation