How to Build - A Next-Gen Game Carby Valentin Nadolu


The Ambient Occlusion Map

This is a bit easier to explain: basically, the ambient occlusion (AO) map contains the amount of „visibility” stored for each pixel. The more occluded that point is in 3d space in relation to its surroundings, the darker the pixel will be on the AO texture. I will not go into detail about how this is calculated, I will stick to showing how it is generated and used. Because occlusion is influenced by all the objects in the scene, this map does not require the low and high-res models to be separated to minimize the number of intersections.

Texture generation is similar in steps to the generation of normal maps. The next image presents some of the settings used. One thing to mention is that for the AO baking, the „Max Search Depth” setting is ignored. This is replaced by „Occlusion Max Distance”, which usually require a value larger than 50 to give proper results.

The value for „Occlusion rays” is directly proportional to the quality of the final texture and the rendering time. For a test render, a value of 16 will be enough, but to obtain a smooth texture, I use a much higher value, usually a power of 2 (64, 128). Be careful, high values in this field will cause the rendering time to increase dramatically!

The resulting image is a grayscale that can be put on top of the painted color texture using Multiply. This will add depth to the diffuse texture, making it look more realistic.


Usually ambient occlusion maps take more time to bake than normal maps, so some patience is required. Do a lot of test renders with low “Occlusion Rays” values to make sure all the details show up on the map before doing a full resolution render that can even take more than half an hour to complete.

            Now that these textures have been baked, you are ready to move on to the next and final chapter of this tutorial, texturing.


The Diffuse Map

The last part of this tutorial will present a simple way to create the textures for this vehicle. I will use as an example the exterior texture of this asset to show an easy and effective way to create textures in layers.

            One important thing that I always keep in mind when texturing is that a lot of times, the texture has to be corrected or changed during the creation process. If I just paint all the details on one layer in Photoshop, later a simple color change can be impossible to perform without redoing most of the texture. That is why the texture should be done in layers, by keeping similar types of details grouped together for easy editing.

            The base is a layer set which contains one layer for each material/color on the texture. Naming these layers in a comprehensive way is a good idea and will make things easier.           



Next layer set up we have the big details in the texture. I used simple shapes and some layer styles to draw the grills. The headlight lenses are taken from a photograph desaturated and pasted as a layer set to Overlay.



After adding the big details, it is time to add some subtle material variation. As this vehicle is new and clean, I only added one layer with a metallic texture set to overlay. To keep everything subtle, the layer opacity was lowered. Also, there is a mask to hide the metallic texture for areas that do not require it. Masking is a good method of hiding detail and it is preferable to deleting as it can be reversed.



The texture still looks flat and lacks depth. To add some variation to the huge areas of blue car paint, I added a new layer of a lighter color, and by using its mask, I blended it with the original one like so: