Hey Morne,
Regarding LWF/Physical lighting + Vray CAM, you can definitely achieve accurate results that require very little posting with a good materials workflow. From LOTS of reading and experimentation over the 8.5 years I’ve been doing this, I’ve found a process that works fairly well for me that is very similar to what others use. From the get-go you want to put some care into preparing & testing your textures & mats. The time expended up front will pay itself back over a couple projects, as you reuse & evolve your materials. If you only think you have enough budgeted hours to ‘fly by the seat of your pants’ pick a couple very important/ubiquitous materials in your scene and really work them.
Most photos that we create our textures from have not been photographed optimally for use in HQ renderings, since they tend to include color casting, illumination/shadows & specular reflections from the environment they were shot in; so generally I work to get rid of all of that duplicate information for the diffuse map using as much non-destructive editing (adjustment layers) as possible in case I test a mat and it needs a bit of tweaking.
After I have derived a diffuse, spec, and bump maps as necessary for the material, I take it over to my V-Ray sun/sky test scene and set up the mat. You want a scene that includes some basic objects to simulate shadowing, reflections, etc. but renders very quickly using good GI settings that closely match your typical production settings. Two very important aspects of the mat test should include observing and tweaking your material’s reflection/glossiness at grazing angles (you can typically use a dark object as the reflectee) and also what I call ‘brightness normalization’ to make sure that your object doesn’t go overbright (greater than 1.0 float) in maximum brightness scenes where the sun is directly over head. So what do we normalize to? Absolute White. Create a VRay mat with a VRay color in the diffuse slot and apply it to a couple objects. Since we don’t want our absolute white to be overbright, we can adjust the output multiplier in the VRay Color slot, thus arriving at a value that will appear ‘color correct’ when rendered. I’ve found about .71 to be the proper value for the RGB multiplier. Use this value to match RGB color swatches that your client has specified. Once you have established absolute white, you can use this as a benchmark for comparing your test materials.
Sprinkle in a few VRay cameras set to F16, ISO 100, Shutter 100 (we’re normalizing using photgraphic sunny 16 rule here) and you’re ready to go. You can also set up a similar ‘indoor’ scene that uses a typical basic lighting scenario to test/compare materials against precedent that typically appear indoors only.
While testing and tweaking my mats, I often use photos as precedent for the material. This helps alot, since materials as we imagine them in our heads are not often how they behave or appear in real life. You should also get your hands on some reflectance & IOR values to help take initial guesswork out of glossies and reflections.
What you’re really doing here is trying to set up relationships between the brightnesses of different materials, so when illuminated they create good contrast in your scene letting you concentrate on refinement in post. After you’re pretty happy with a mat, save the sucker to your library, and it will be ready to drag and drop for your next outing. You can always refine it again later. Having some knowledge about the physical behavior of light and materials will make your renderings better; but as you’ll hear often--the art of VIZ is really about making it look good; so have a drink, use your best judgment, pass off some pics for critique, and have some fun making nice stuff.
There are many good threads regarding these topics around the forums, which you should check out. I’d provide some links, but I have to hit the sack over here for some skiing in the AM. Hope this helps!
Cheers!
Dave