The Poly Select Modifier is a modifier that lets you pass a sub-object selection up the modifier stack. This is very useful especially for complex objects that needs different UVW Map preferences for different parts of the object. Great for objects with Multi/Sub Object Materials.
So I have this object that has 3 Polygon: Material IDs – ID 1 for the wood, ID 2 for the pattern graphic, ID 3 for the counter. I apply the Multi/Sub Object material and then go to UVW map the object but one UVW map modifier is not going to work for all sides and all Material IDs. So here is where poly select comes in handy.
1. I place a UVW map on the object for the wood that works for the majority object. I do not like the orientation of the wood grain for the top/bottom or the angled extrusion but I fix that in steps 4 & 5. Next.
2. I placed a poly select modifier, then use the select by Material ID 2, and then place a UVW map modifier. I adjust UVW map preferences and it only effects the polygons selected in the Poly Select modifier.
3. Similar to step 2 I pace another poly select modifier, then use the select by Material ID 3, and then place a UVW map modifier. I adjust UVW map preferences and it only effects the polygons selected in the Poly Select modifier which is now Material ID 3.
4. Now to fix the wood grain on the top and bottom. Repeat the process and place another poly select modifier select the top and bottom polygons, and then place a UVW map modifier to have the grain go the other direction.
5. I would like the wood grain on the angled piece to follow the angle so I add yet another poly select modifier select the front and back polygons on the angled piece, then add another UVW map modifier and rotate the gizmo to the same angle as the object.
6. Is the Final Result with wood grain going in the correct direction on all sides, the pattern graphic filling the whole polygon, and the counter specs at the correct scale.
I use this method if doing architectural stuff quickly and this is faster than unwrapping the object and texturing in Photoshop. I also use this for baking procedural materials on unwrapped objects. For baking set your Unwrap UVW modifier channel to 2 and the place all the UVW maps modifiers to channel 1 then you can bake those textures right onto your UVW template and get the texture scaling consistent throughout the UV template.