This page provides a guide on rendering the required passes in V-Ray for NUKE to create a traditional beauty pass and then how to properly composite them back together.
Page Contents
Overview
In this tutorial, we will set up a NUKE script to render out the required passes in V-Ray to create a typical beauty render and then show how to composite them back together. This allows changes to be made on each Render Element in Post without the need for re-rendering.
Part I: Setting up the Render Elements
In this first section we set up the Render Elements to composite into a beauty pass in the last section. Although the scene setup we are dealing with is actually rather complex, many sections have been grouped together into a single node for the sake of visual clarity. If required, these can be un-grouped into their original form by going to the Edit menu's Node section, then to the Group section and clicking on Expand Group (or by simply using the Ctrl+Alt+G hotkey).
The Node graph at the start of this tutorial
Set up the Scene
1. Create a Scene node after all the geometry, materials, and lights in the NUKE script, and name this node RE. We will be connecting all our render elements to this to keep things ordered.
3. Ensure that the RE Scene node is connected to the VRayRenderer node.
Set up the Lighting Render Element
1. Create a VRayRenderElement Node.
2. When the Select Render Element Type box appears, select Lighting from the Type drop-down.
3. Connect this node to the RE Scene node.
4. Repeat these steps for each of the other required Render Elements (GI, Reflection, Refraction, Specular, Self Illumination, Atmospheric Effects, SSS & Background Render Elements).
Additional Render Elements will be needed (such as Self Illumination, Atmospheric Effects or SSS) if the scene characteristics require them. However, if they are not present then they are not needed to re-create the final Beauty composite. In the example shown here, as there are no objects within the scene with refractive or subsurface properties, those corresponding Render Elements are not needed. Since there are no volumetrics in the scene, we also don't need the Atmospheric Effects Render Element.
Part II: Rendering out the Render Elements
In this section we render out the passes we need to composite back together our beauty image.
Set the Render Elements Location and Name
1. Create a Write node and connect it to the very end of your graph (after the VRayRenderer node).
2. Make sure that in the Write node the Channels are set to RGBA so that only the beauty channel is rendered out.
4. Under file in the Write node, set the name and location of your choice.
5. Set file type to exr.
6. Create an additional Write node for each render element, making sure each has its channels option set to the appropriate pass and is named accordingly.
Set the required frame range
1. With the Write node active, click the Render button.
2. When the Select Render window appears, in the Frame range set the required frames you wish to render. For a still image, the range will be 1-1. For a sequence, the range will be something like 1-100.
Render out the Render Elements
- With all of the Write nodes selected, press F7 to render all the selected Write nodes.
Lighting Render Element
GI Render Element
Reflection Render Element
Background Render Element
Specular Render Element
Self Illumination Render Element
Part III: Compositing the Render Elements into a Beauty Pass
With the render elements now rendered out as EXR files, we will read in each pass and composite these together to recreate the beauty pass. This gives greater scope for tweaking the individual render elements to change the look of the beauty pass without the need for re-rendering.
Render elements can also be outputted as separate images or image sequences as well as a multi-channel EXR. In some pipelines, it can be advantageous to render out as separate files for each render element, although in most cases a multi-channel EXR sequence is easier to handle.
Set up the scene
1. In an empty NUKE script, create Read nodes for each render element.
Adding Merge Nodes to each Render Element
1. Create a Merge node and set its operation to plus.
2. Connect the B channel of the Merge node to the GI Read node and the A channel to the Lighting Read node.
3. Create copies of the Merge node for the other render elements and connect the A channel of each one to its matching render element's Read node.
4. Connect the B channel of the Merge node next to the GI Render Element to the Lighting shuffle node.
5. Connect all other B channels to the previous render element.
The final node graph to recreate the beauty pass from its component render elements
Original Beauty Render Element
The beauty composite with a glow added to the Self Illumination and Background Render Elements
Notes
- The Self Illumination and SSS Render Elements are only required in the rendering/compositing process if they are used within the material properties of objects in the scene.
- The Atmospheric Effects Render Element is not required unless the scene is set up with volumetric properties.