- Color maps should be created while at the highest subdivision level.
- Normal maps can be created a few levels below the highest or at level 1. Which depends on whether you’re going to be doing a displacement map as well. If you will have a displacement map, drop down just a couple levels from the highest and create your normal map. Then delete the higher levels and drop to level 1 to create your displacement map.
- Displacement maps should be created at level 1. Be sure to restore your base mesh prior to creating the map.
Creating both a normal and displacement map gives fast renders. Normal maps render more quickly than displacement maps, but because they don’t change the silhouette of the model they only work well for high resolution detail. Displacement maps change the silhouette, but this isn’t usually visible with high resolution details. So while they can certainly be used to create all details they give the most bang for their processing buck with medium resolution details.
In all cases, the size of your map is what determines how much detail it can hold. A 1K map (1024x1024 in size) is just over 1 million pixels in total. A 2K map is about 4 million. A 4K map is about 16 million. In practice, about 25% of the available pixels aren’t used, though, because almost all UV mapping has empty space. Your goal in determining your map size will be to choose the one where the available pixel count is closest to the number of points at your highest subdivision level. So if your model is 4 million points, then a 2K map is perfect while a 1K map would lose a lot of detail and a 4K map would require a lot of interpolation to create extra data out of thin air (resulting in quality loss).
The exception to this final rule has to do with displacement maps. ZBrush has a feature to increase the fidelity of a map when the polygon count wouldn’t normally support that size. This is the DPSubPix slider, which specifies a number of virtual subdivision levels ZBrush will create when calculating the map. So your 4 million poly model could have a 4K map by using a DPSubPix value of 1. This divides the model once in RAM before creating the displacement map, bringing the 4 million poly model to 16 million points so that your 4K map can be created perfectly. Higher DPSubPix values would be a waste of time and resources in this example because they’d divide the model significantly farther than a 4K map can make use of.
One final note: You will notice I only talked in terms of general subdivision levels rather than saying something like, “Make your normal map while at level 3.” This is because a model that starts with 100 polys will have a radically number of points at level 6 than a model that started with 1000 polys. You never really need to care about specific levels for this reason. What you need to pay attention to is the number of points.