|Build a NextGen Game Car: Part I [High-res Modeling]|
Software: Autodesk Maya
Author: Valentin Nadolu (AMC Studio)
Author Website: http://www.amc.ro
About this tutorial:
Written by Valentin Nadolu
This tutorial is intended to present a method of creating a next gen vehicle asset. The difficulty level is medium, so to better understand and use this tutorial, the reader needs to have a basic understanding of the processes involved in modeling and texturing an object in Maya. The asset presented here will be a generic vehicle with a low polycount that has diffuse, specular and normal map textures.
The descriptions will therefore be general but I will go into detail to explain the particularities of next gen asset creation every time it is needed.
To make the work easier, this tutorial is split into five different parts:
I. High-res modeling
II. Low-res modeling
III. UV layout
IV. Texture baking
V. Texture creation
One important thing I have to mention beforehand is that saving the scene as often as possible is a very good idea, especially when working on a complex asset such as this one. Maya's incremental save feature is good, but saving one new scene for each major step of creation will ensure plenty of back-up scenes to go back to in case you need to.
Often, modeling a vehicle is easier when official blueprints are available, but there are situations when these are not available, so the modeling process has to rely entirely on reference photographs. There are also cases when the entire documentation of a vehicle is reduced to a concept sketch. This is the case for this tutorial as the only reference I have is this perspective drawing of a concept car I drew. To make things easier, I also sketched a simple side view to help me get a better idea of the proportions of the vehicle. I will modify some of the shapes of the vehicle as I model it to improve its shape, as it is usually acceptable to do some modifications to the initial concept.
I. High-res model
The first step of the process is also the most important as the high-res model defines the general shape and proportions of the vehicle and will have a major impact on the entire asset creation pipeline. Usually, modeling the entire car in high-res is not required, but for this tutorial I will model everything that is visible in the final model.
A good starting point is the wheel placement. The resulting "frame" will give you a good starting point for defining the car's proportions.
Even thought the car is not even started, the wheels will help define the car's front and rear width and wheelbase as well as wheel dimensions.
I start by placing a single polygon at the right-front corner of the car and matching it to the side drawing. Then I extrude another polygon from one of its edges. After each extrusion, I check the newly created vertices and move them in both the side and perspective view to make sure they are in the right place. This procedure can be extended to the entire car, but I only use it for the general shape. For the details I usually use polygon primitives as base. there is another way to build the mesh by using the so called "box-modeling", but my personal experience has taught me that the multiple extrusion method is a bit faster and easier to grasp.
Continuing the side of the car, I will add the details by cutting the geometry using the Split Polygon Tool. I try to keep the polygons evenly spaced to make the mesh as optimal as possible.
After defining the cut in the side view, I move to the perspective view to adjust the vertices.
After that I return to the side view and do some more adjusting.
It is vital that the artist checks the polygons he just created as often as possible and from as many angles as possible. Checking will probably take more time for each new part/polygon than actually creating it, but this is necessary to ensure the quality of the work.
By extruding, cutting and moving vertices around, this is how the side looks like:
The basic shape can be obtained by extruding the border edges of this geometry. Notice I haven't extruded the bottom part as it is not necessary to have that area high-res.
Next is the front air intake, the smaller front side intakes and the basic shape of the headlight:
I then cut the shape of the glass roof from the main body geometry. I will use the extracted faces as a base for the roof. To get a better view of the entire car I duplicate the side as an instance and scale it by -1 on the x axis.
For the security arch of the glass roof, make a copy of the glass roof and then cut a shape using the Split Polygon Tool, which will then be extruded to get the desired shape.
The basic shape might be done, but the silhouette is not as the car looks "square" when looked at from the front, back and top views. This is because there is no direct reference for these orthographic views.
This problem can be corrected by using a lattice modifier on the body to modify its general shape. This method is good when the result is "square" and will add a new dynamic look to an otherwise dull looking model. The command can be found under Create Deformers->Lattice. I used these settings but the different parameters can be changed to better suit each vehicle:
As the basic shape of the car is ready, I will save a separate scene with this geometry to later use as a base for the low-res model.
With the final shaped improved, I can then move to modeling the medium size details like intakes and outlets. Here is for example how I added one of the frontal intakes:
As you may already know, the modeling process should be done by using 4-sided polygons, generally called quads, to avoid any artifacts when applying Smooth on the mesh. Triangles are to be avoided; in turn it is preferable to use polygons with more than 4 sides if absolutely necessary. Usually a 5 sided polygon doesn't affect the smoothed shape too much, but checking if it does affect the mesh will determine if it is ok to use it or not. Here is an example of such a case (the selected polygons are five sided). The second image shows that area with one level of smooth applied. As you can see, the five sided polygons do not affect the topology too much so they are acceptable in this situation.
The wheel will use a polygon cylinder primitive as a base. This cylinder will have about 4 times as many divisions as the number of the spokes the wheel has. My wheel has 5 spokes so the cylinder will have 20 divisions.
I only keep a "slice" of this cylinder and instantiate it to reconstruct the wheel. This way I can work on one segment and visualize the entire wheel at the same time.
To make the wheel look more realistic I separate the tire from the rim. Adding a "lip" to the rim will also help differentiate the two pieces.
Being a sports car, the rear wheel will have a "deep-dish", accomplished by simply moving the center of the rim inwards. Small details like this go a long way to make the car look believable.
There is no interior modeled for the high-res wheel as this area will be barely visible on the final car and therefore will not require any special details on the normal map. This is often the case with high-res models that are going to be used only for baking maps as there are some areas that need not be modeled because they will not influence the final low-res model.
One thing to be careful about are the geometry intersections. These are to be avoided because they tend to cause problems. To minimize problems, some of the topology might have to be rearranged to make the separate pieces match at a vertex level. This way, the smoothed meshes will intersect without causing rendering problems.
Before applying smooth, some of the edges of the model have to be "strengthened" by adding some parallel cuts to them. This can be done by using either the Split Polygon Tool or Select Ring and Split Edge Ring.
For the wheel cut-out, a small extrusion will make the area more believable as most cars have this detail.
The same detail, applied to the rear wheel:
One thing to be aware of is that for the seams between parts to look good, the topologies have to be similar and the meshes should have matching vertices on the borders. This will ensure the objects will have identical borders even when smoothed.
Going further into detail, the headlight can be modeled from separate pieces to keep the process simple. The interior and glass have both been constructed from the geometry already done for the exterior of the car. The only scratch made parts are the cylinders inside.
The brake disk is one element that doesn't require too much detail as it will not be too visible on the final model. Modeling the big details is enough as smaller ones like slots, holes, grids, rivets can be done with textures. To further optimize it, I only modeled the details that face the exterior of the wheel, leaving the interior face flat.
The best way to start the interior is to use the exterior as a base. By extruding the borders of the exterior inwards, the interior can be created very easily. The next couple of pages contain some screenshots describing the way the interior was built. There are not many descriptions as most of the images are pretty easy to follow.
The engine bay:
The cockpit and door:
For the door I used two already modeled pieces of geometry as base:
-the door thickness is made using a part of the cockpit. (selected in the image)
-the exterior of the door was already created when I did the exterior of the car, I just have to combine it with the thickness
-the interior of the door is the only part that has to be scratch built.
The steering wheel:
The base is a simple torus primitive. The interior is made from a simple plane modeled to the desired shape and then extruded.
And finally, some screenshots of the finished interior:
As you can see, the level of detail in basic, as the interior will not need too much normal map detail apart from the general shape. Adding small details is done in a much faster way by using textures.
Next chapter will deal with the ingame geometry and the challenges of keeping the model as low on polygons as possible.
Download Hi-res Car Concept Sketch
All links for this tutorial:
1. Build a NextGen Game Car: Part I [High-res Modeling]
2. Build a NextGen Game Car: Part II [Low-res model]
3. Build a NextGen Game Car: Part III [UV Layout]
4. Build a NextGen Game Car: Part IV [Texture Baking]
5. Build a NextGen Game Car: Part V [Texturing]