CAR MODELING PROCESS

Today we decided not only to tell you, but also show you step by step how three-dimensional models are created. Let's take for example car called Azov, created by our artist for the game SnowRunner.

Step 1. Refs

As a rule, a prototype of a real car is chosen as a basis for development, on the basis of which (or close to it) the geometry is collected.

It is important to approach the process of collecting references very seriously. The reference of only one or a group of elements of the machine can be dozens of photos. It concerns, for example, running gear, saloon, a cabin. Also you should remember that one and the same car can have different modifications. And in this regard, it is important not to mix the options of one modification with another.

YouTube or other video services can help you find references. Search for videos in which the author walks around the object or twists it in his hands. You can make screenshots of the necessary angles and details. Of course, video search is often more difficult than photo search, but it can be much more informative.

And do not forget about various technical documentation. It can help a lot too.

Step 2. The base model (BM)

This is the so-called assembly of the geometry from the "primitives". It is needed in order to get the overall shape and maintain all proportions. This step does not provide excessive detail - we take into account only the formative elements.

Step 3. The detailing of the basic model

Once we have got the general shapes and are sure that everything is in place, it is time to start detailing the BM geometry. At this stage, it takes on a pre-Haipo state and topology. It is very important that the model retains its functionality, so we assemble it "as in life". This means to avoid intersections of elements, as well as holes, hanging geometry and other things.

Stage 4. High poly

This is a very important part of the design. The quality of the entire model, right down to the textures, will depend on the quality of the geometry. When working with the form, it is important to do the correct shading (machines are particularly demanding). Bad shading can affect baking and normal maps, as well as ruin the final result at the texturing stage. This is where your knowledge of topology and shading retention methods comes into play.

Also, don't forget about floaters. They are very often used when working with high poly, and it's important to stick to some rules:

1. If the floater creates problems with the convergence of the floater shading and the supporting geo, it is worth trying to sew the geometry or use ZBrush.
2. The floater should not be placed far away from the main geometry. In that case, the normal map will probably bake in without problems, but there will be AO left over from the floaters, which will cause you to have to do a lot of "mashing".
3. Some floaters can be left to "float" over the geometry if the distance between them is small. But if it's a deep floater, you need to make a hole underneath it in the main geometry where you can deepen it to avoid shading when shaving the AO.
4. If your working 3D package supports ShrinkWrap modifiers - this will make it a lot easier for you to work with floaters. The shading will be perfect.

Step 5. Low poly

When working with low poly, we rely on the shape and level of detail depending on how close the player will be to certain objects. In the case of the car, we do two levels of detail of the cabin. So we have two versions of the geometry with a high and a low level of detail (in terms of the number of tris). But both cabs retain absolutely all elements that are baked with the same high poly geometry.

The HD cab has a much higher texel and polycount than the cab designed for 3rd person observation. After all, the dashboard must retain all the inscriptions and markings that are shown on the references, photos, in the documentation of this car. At the same time, the cab with a smaller texel (LowRes) has a lower level of detail than the HD in terms of texel and polycount, but repeats all the elements from the dashboard, preserving the detail, and fully duplicates the appearance from the main version. We will talk about this a bit later, in the bake section.?

Stage 6. UV

When working with UV, it is very important to stick to a number of rules:

• Split on UV is not always = HardEdge, but HardEdge always = Split on UV.
• After the cut, you should not put HardEdge everywhere - that is, on the UV borders - on shapes like cylinders/spheres. The HardEdges at the cut should be removed. After you've cut everything, the UV islands need to be aligned vertically and horizontally (within reason). Remember, the quality of your UV map affects the overall quality of your model. The density of your packing, and therefore the baking and textures, depends on it.?
• Just cut and pack (no UV shelf alignments) = bad texel = bad packing ---> washed out and poor quality textures.

Shells are aligned within reason. If aligning the shells leads to a lot of pull, because you have a complex shell shape. You may want to try to make the cut elsewhere, or leave it as it is in case this shell is going to be one of the few on the Udim.

Step 7. Bake

The baking takes place in a standard way. It is important only to consider an important aspect - the moving elements of the model. You can't have AO or normals from neighboring parts (if you haven't baked the parts that will be later animated).

When we bake the HD version of the cab, our main task is to chamfer the HP geometry well. Usually there are no problems with it, because the polycounter allows us to control every object, even the smallest one. At the same time with the LowRes version, things are a bit more complicated. Here we have to bake a lot of details in one plane and we can't allow distortion of the normal map. The Skew mode in Marmoset Toolbag can help with this. This feature allows you to align the projection direction for correct baking, without skew and distortion.

Step 8. Texturing

In working with the textures we use a large number of references - those that were collected in the first stage, plus take additional references cars with different degrees of contamination and in different technical condition (new, old and so on).

Even a picture of a rusty hood of a car you saw in the parking lot next to your office will be a great reference for the artist (even though the owner of the car probably does not agree with you :)).

Working with textures is a very time consuming process. It is divided into several stages.

Since we are texturing in PBR (Physically Based Rendering) pipelines, we stick to the division of working with metals and non-metals, and define all the materials in their places according to the references.

After we have applied all the materials, we begin meticulously working with the Roughness and Metalness channels. First of all, they will show the interaction of the surface of the object with the environment through reflections - and only then can this be reflected in the color of the object.

Then comes working out the color, the level of wear and tear on the machine - it all depends on your technical specifications. This is where the painstaking artwork begins - we can't rely on automatic generators for everything. All chipped paint, scuffs, scratches and traces of dirt in places which can't be "reached" by generators on AO, curvature and other maps, we do by hand. Again, first of all, sticking to the references.

And after all that, you can say your 3D car is ready. Of course, we only went over the top and considered a certain "ideal" situation in which no problems arose. But hopefully you now have a general idea)