Section 2: Materials
Fig. 1: the final render this is what you will get at the end of the 2nd part
The most important thing about the material i used on the Nissan, is that after various tries (where i just put a coloured bitmap in the diffuse channel of a generic paint-like material), i went for a more complex and relistic approach: using a complex "blend" material i was able, with simple masks, to "paint" the car with different paint materials (white, red, black...), each one with its own characteritics and parameters. The result is a more realistic output, like the one you can see in Fig. 01.
Section 3: Mapping and definition of UVW coordinates
Mapping a model is a process to let 3ds max know which parts of a bitmap are to be where on the model itself. In the simpler situations, standard mapping options in 3ds max can be enough (for objects similar to spheres, cylinders, cubes..), but, as the model gets just a bit more complex, these methods are no longer enough.
Fig. 2: UnwrapUVW what we should get at the end of the mapping process
Fig. 3: Mesh Select select the highlighted faces
A correct mapping has to achive 2 main objectives: you must be able to paint simply and intuitively your textures (Fig. 02) and it must not lead to any distortions or arefacts in your renderings. Luckily enough, cars are generally built with big almost planar surfaces, and this greatly simplifies our task as we can almost always use planar mappings and get good results with small tweaks. Let's see how we can map the Nissan's bonnet: at this stage we have objects with a modifier stack like this: Editable poly > Simmetry > Meshsmooth.
Fig. 4: UVWMap align the planar gizmo
Fig. 5: UnwrapUVW check the mapping
Let's apply a "Mesh select" modifier between the "Simmetry" and "Meshsmooth" modifiers, go in "Polygon selection" mode (by clicking on the little red square in the modifier panel) and select the faces as shown in Fig. 03: as you can see, this selection can be mapped with the same planar mapping (excluding the area inside the headlights, but there will be just black paint so we can go on without caring about this area). By doing this selection, we assured that the next modifier in the stack will work only on the selected polygons: let's add (without deselecting the polygons and leaving the small square icon clicked!!!) an UVWMap modifier, and select the "Planar" projection option.
Align and adjust the planar projection gizmo like in Fig. 04, helping yourself with the "fit" button and the alignment options (in this case i aligned it to Y axis).
Be sure to make the gizmo square by changing the values to suitable ones (ie clicking "fit" i got a 193x136 gizmo, which i rsized to 200x200). At this point, add a Unwrap UVW modifier to the stack (always BEFORE the meshsmooth) and take a look at the mapping so far achieved by clicking on "edit" in the modifier panel (see Fig. 05).
Fig. 6: Mesh Select select the hilighted faces
Fig. 7: UVWMap align the planar gizmo
Fig. 8: UnwrapUVW check the mapping
Add a new Mesh Select modifier and select polygons again, as in Fig. 6. Add another planar UVWMap modifier as in Fig. 07, making it square as before. Add another UnwrapUVW and check the mapping (Fig. 08). To the same for the left side of the bonnet (Fig. 09 and Fig. 10).
Fig. 9: Mesh Select select the highlighted faces
Fig. 10: UnwrapUVW check the mapping
Fig. 11: UnwrapUVW check the mapping
At this point add another Mesh Select modifier and DO NOT select anything, so the next modifier will work on the whole object. Add an UnwrapUVW modifier and click on "Edit" to see how the whole surface has been mapped. As you can see in Fig. 11, the 3 elements are overlapping: this is easily fixed by selecting the scale, rotate and move tools in the editng panel and checking the "Select element" option. This way you can easily accomodate the 3 elements in the square area as in Fig. 12.
As you can see, the selected element in Fig. 12 has to be mirrored (just click on
the "Mirror" icon) to get the proper mapping (Fig. 13). Also the main bonnet surface is somehow mirrored (i realized this only after the first test render), so just do the same operation on the main surface.
Sometimes (Fig. 15) having the textures projected on the eding window is very usefull to ad just particolar vertices and to check for distortions with a visual feedback: to achieve this, you have to click on the "Show map" button and choose the texture you want to see. If you cannot see anything on the background, chances are that you simply need to push the "Brightness" value in the "Show options..." panel to a value greater than 0.
Fig. 12: UnwrapUVW adjust the mapping
Fig. 13: UnwrapUVW adjust the mapping
Fig. 15: UnwrapUVW checking the textures on the model