LightWave renders are displayed once rendering has finished, and can be used as is but there is a lot more power if you use the buffers LightWave provides to create your images - you can save a lot of rerendering too.
What Color Space Should my Buffers be in?
The Dragon here shouldn't have much color in the diffuse channel because the dragon is metal. Only areas where the verdigris shows through have diffuse color, and so, in Linear, the dragon is almost black. Switching the Image Viewer display to sRGB gives us a better view of the diffuse component but such a view is only better for our eyes, not the compositing package.
When you first render an image broken down into its buffers for compositing, it can be unsettling to see how dark the resulting images can be. The simple answer is that the renders from LightWave should be saved as Linear, no color space manipulation at all, and then the compositing application will output a color-corrected sequence of images as the end result. At the same time, nothing prevents you from applying a color space to Image Viewer to better preview what that compositing end-result will be. Just don't save that color-corrected image for use in your pipeline.
Some buffers purely represent data, Object ID and Surface ID are the only two right now. These will be presented in clown colors in Image Viewer but the saved image files will seem to be white. There are varying tones indicating discrete elements, but a normal screen can't show them.
The Surface ID buffer as seen in Image Viewer (left) and the resulting TIFF file (right)
There are a lot of buffers, but they break down into the following categories:
Buffers with "Direct" in their name show scene elements that are directly lit by scene lights. The Diffuse Direct is how the color of objects with roughness is seen. Specular Direct is the flash of light off a shiny metal of a car hood, for instance.
Buffers that have Indirect in their name contain the elements of the scene that are lit by light that has bounced off other objects, or the environment. For the Diffuse buffer, this will mean the ambient color of an object in your scene or one that has received the bounce coloration in a radiosity render.
The Rho is the weight of reflection of light. In other words, the amount that shader will reflect back - the Specular Rho is how much specular reflection is calculated. This shader has a more complex explanation but is very powerful. An example would be to have a scene with copper spheres that your director decides should be gold. You can isolate the copper spheres in your scene using the material or id buffer, and divide the masked image by your Rho buffer. This removes their color. Now, take a copy of the Rho buffer that has been recolored to gold and multiply that with masked render. You now have gold spheres without having to rerender the whole scene. You could have tried to eyeball the change and isolate out the spheres to touch up their "paint job", but doing it with Rho buffer manipulation will be truly correct; for the colored lights in your scene, for other objects, for your director, and you.
Probably not a buffer type you'll use a lot, it's fairly specialized. Weight buffers are scalar and add up the contribution of a buffer type to a finished render. You might have one shiny penny in a scene with many dirty ones, so the Specular Weight buffer will highlight that shiny penny for you since it's the element with the most specularity in the scene it will be brighter than the other pennies. You can also use to alter the proportions of different buffers in a scene - upping the clearcoat in a new car scene, or changing the dermis and epidermis weights in a scene with lots of skin.
Some buffers render in so-called clown colors in VPR, and also for display in Image Viewer. This is only for simplifying the concept
The Back to Beauty - Rendering for Compositing example will show you how to combine your buffers for the image you are trying to create.
The Render Properties' Buffers tab shows available buffers organized into groups. They are:
These are buffers which the render engine itself makes available.
These are buffers which shading system elements, such as the Material nodes and Shading Models, provide.
This group contains any existing Light Buffer Groups. Each of the groups will contain its own set of the buffers which are known as "Direct" buffers, since this data can be broken out into a Light Buffer Group specific buffer.
Custom Buffers can be created to fulfill specific purposes, like breaking out surfaces of an object. They are stored with surfacing, so loading an object that has a Custom Buffer will add that buffer to the system.
Buffers can have a large amount of data in them, represented by different colors. The means of displaying these colors depends on the format output.
The Compositing Buffer Export Image Filter has been moved to the LightWave Legacy plugin archive.