When I was happy with the look of the model and I got it approved from my friend too, I moved on to the UV. At this point I had a reasonably good idea of how much detail I would need, and which areas would require more care.
I split the vehicle into six areas of roughly similar volume: front, main, rear, framework, wheel and another one for all the small details. I kept the rifle separate, since it was going to be used also as a separate asset. Each became a UV tile, and had a 4096 x 4096 texture (Fig.06).
It is very important to maintain a similar scale all across of the model when doing the UV. Often, during the process, I shift some geos from one tile to another if I can't get enough space. Keep a checker shader handy to constantly see if everything matches. Similar scale means the same level of detail across different objects, but also sharing the same maps during the texture work.
I try to avoid any kind of overlap, even if I have many insignificant objects that could share the same UV. That gives me full control during my texturing work, and helps me to avoid nasty results that I'll have to fix when I'll bake the maps.
Texturing and Lookdev
Before I start describing my work process I want to spend a minute explaining a couple of things about gamma and LUT. There are plenty of tutorials and discussions on the forums on this topic, and many different settings. I don't claim that mine are the correct ones; I'm just sharing my workflow.
In the Gamma and LUT settings of 3ds Max you can decide how your render engine and your viewport are going to handle your images and textures. Enable it, but leave everything as it is (Fig.07). Otherwise you will display overexposed textures in the viewport and you won't affect V-Ray at all (A - B). V-Ray has its own panel with LUT settings for the render, and those are the settings that count in the end. Max or V-Ray framebuffer will show the same result.
I don't use Gamma 2.2. Dark areas come too bright, even for daily exteriors like this one. I tend to keep it at 1.8; it gives a better contrast to the renders (C).
In Max's viewport I keep my models in constant color while I'm working on the textures, so I can see exactly what I'm doing in Photoshop, and I don't get distracted by the shading. If it's looking nice with flat colors, it's going to look even nicer once it's shaded.
Even with an extremely powerful render engine like V-Ray, I don't expect it to do all the work for me, and I try to make my diffuse textures appealing and the shapes of my models recognizable even without any lighting.
Texturing is the most important part of creating a great model. You can let an average model shine with fine texturing work, or an outstanding model can be very plain and boring. All the shading process, specular, bump, etc., will help, but the diffuse have to be flawless first.
Here is the basic workflow I used. First of all I decided on the overall color for the entire vehicle. It had to look like a police force vehicle, so I did some research for police force vehicles. Dark blue with red stripes is the typical color scheme of the Italian police force: the Carabinieri. I tried different palettes (grey/orange, black/red), but eventually I chose this one (Fig.08).