Leonardo Branco is 2D and 3D artist with 18 years of experience producing art content for games. In this tutorial, he shows how to model, retopology and texture a low-poly game asset.
In this tutorial I’ll try to cover in a very elementary and practical way all the steps I took to produce this asset.
First, a little background. “Shield Libitina” was an asset produced for the game “Blood & Glory”, from Glu Mobile, in 2011 and was conceived to be the most expensive of it’s category in the game. Our objective was to create an extremely detailed object, that had to stay below 1.000 polygons and had to make use of only 1 material and 3 texture maps. A normal, a diffuse and a specular map, because we were using a very customized Unity 3D’s Shader, back then.
Walfrido Monteiro, the concept artist by the occasion, came up with this great design! To see more of this great brazilian artist, check out his personal site.
Once a concept is approved, I start to work on the high polygon model, or the “reference” model. For this sculpting stage, I always use ZBrush. In ZBrush, I start “extracting” the silhouettes of the pieces from a 3D plane, using a mask made from the very concept.
I did this for the “Base” and the “Frame” of the shield.
After that, I start to model the general shapes and volumes of the pieces in a very rough way. The goal here is just to find the volumes and proportions of the piece, so we have to resist the temptation to start creating details at this point, to avoid losing time.
When the volumes and proportions are defined, the real fun begins. It’s the most time consuming stage of the project and also the most pleasant for me: the sculpting of all the ornaments.
After making about 4 to 5 subdivisions, I found that the best way to sculpt the ornaments, was to make continuous and decisive brush strokes, using the “lazy mouse” feature (setting from 30 to 50) and the clay brush. I chose this method instead of using masks and inflate them, because of the intrinsic relation of the ornaments. It was easier and faster, for me, to draw the ornaments and its relations, instead of drawing the masks.
To finish with the sculpture, I modeled the handle, some minor details and put the buttons on the cushion at the backside of the shield. Now it’s ready for the painting job.
I did all the painting inside ZBrush and started with a very dark primer to act as base. This will help enhance the granular effect I was looking for.
After covering all the pieces with an almost black color, I make a cavity mask to preserve the dark color on the cavities and start to paint the respective color base of each piece with a very granular brush setting, as show in the figure above.
Now is time to invert the mask and get rid of the black areas on the cavities. The idea is to paint those areas with a darker color than I had painted the higher areas.
I just kept doing so for the rest of the pieces, using their respective color bases, until all the pieces were painted.
The asset are now ready to one of the process I like the most, RETOPOLOGY!
I know many people will say that with the advance of some technologies, to do retopology manually now days is nonsense. What can I say!? I’m from the old school! I just can’t let a program, figure out an automatic solution for my lowpoly models! I never found an automatic solution that could be better than a well trained eye, principally when the polycount drops down of the 4 digits. Don’t forget that this asset was planned to be used in mobile devices, and have a lot of silhouettes. Of course, some “low poly” models for consoles platforms are an other history! Some main characters from an AAA title can easily pass the 70.000 polygons. That is a lot of vertices to brush! You’ll get old and will not finish the job! Then, for those cases, the more automation the better!
Anyway, I think making retopology manually a lot of fun and I use “TopoGun” for that. It’s worth giving a try.
For those who are not familiar with the process, in practical terms, retopology is the task of creating a new optimized model using the highpoly model as reference (guide). Basically, we create a new mesh enveloping the shapes of the highpoly model in a very rough way.
Now that I have my lowpoly mesh, I load it in 3D Max to set the UV map.
With the UV properly set up, I come back to TopoGun for the “baking” process, or the process to generate the textures. This action will project or “capture” all the details of the highpoly model within the UV’s layout of the lowpoly mesh. Sometimes I also use the “XNormal” program to execute this process. From this, I get the holy trinity of the texturization process….the COLOR map, the AMBIENT OCCLUSION map and the NORMAL map. There are many other image kinds like, cavity maps, curvature maps, thickness map, etc….but with these 3 guys we can go anywhere or make almost anything.
In Photoshop, I blended the color map with the ambient occlusion to get the diffuse map. Tweaking the diffuse map I made the color specular map (with an alpha channel controlling the glossiness and intensity). Notice that these process was the default for traditional shader system back then. To use the PBR (Physically-based rendering) approach, the textures’ arrangement need to be much more elaborated.
And that is all the work done! You can see the result below:
I hope this humble article may have been of some entertainment or utility, for those who are so fascinated by the 3D universe in real time as I am.
Thanks for the reading and for your interest!