Dev Diary: Creating Tile-Based Texture Maps for Games

One of the key difficulties in creating good looking ground materials is trying to stop visual repetition when seen from a reasonable distance. There are many techniques that can be used to achieve this including detail textures, various methods of blending between textures, and tile-based texture mapping.

In Path of Exile we use tile-based texture mapping extensively to break up the repeating patterns that would otherwise be very unsightly. One problem is that there is very little in the way of information for artists about how to create tile textures. This tutorial is designed to give some insight into the process we use when creating these textures. Read More.

Technical Overview

Step 1: Source Textures

Step 2: Stitching Together

Here the textures were put together in different layers in one big 1024x1024 map with some basic fixes such as lens correction to remove distortion and some vertical perspective depending on the base texture.

The perfect base texture for a ground texture is taken far away straight onto the surface. As this isn’t always practical, most photos will be taken with the lens close to the ground with some lens distortion. You also often get some vertical perspective as the area photographed is limited by the feet of the person taking it, causing the photographer to take the shot aiming slightly forward rather than straight down. In addition to the lens and perspective correction, hue/saturation, match colour and brightness/contrast were used to make the photos fit better together. Any seams within the texture can be fixed by erasing the upper layer in which they can be seen.

Step 3: Getting Uniform Luminosity

In this step I want to get rid of any large differences in luminosity within the texture to help it repeat better. To the left below you can see the big differences in luminosity if the texture is repeated next to itself.

This is something you can do quite late on a "normal" repeating texture, but here I need to do it before I fix the large number of seams, as a blurred layer above would affect the seams if it's done afterwards instead of before.

The steps taken for this in Photoshop are: merging all to a single layer, duplicating that layer, invert, desaturate, blur and then set to overlay. You can then adjust the layer with brightness and contrast if needed. The overlay texture that is created with this process is shown here in the center.

On the right is the texture tiling with itself after this process. As you can see the texture now has a uniform luminosity and so it tiles much better.

Step 4: Adding Details

Here I brought in another texture I made before to get some interesting grungy damp moss in between the stones. By putting the moss texture on top at 50% opacity, I could manually erase the parts that would cover stone that I wanted seen. I ended up using a layer with 33% opacity and another layer on top set to overlay on 33% opacity. Both of those layers were adjusted with brightness/contrast. In retrospect I probably could have skipped this step as it didn't turn out that well. This type of thing can also be added as a last step with some extra work which will give you two different textures you can use.

Step 5: The Tile Grid

Step 6: Assembling The Seams

One seam section is chosen and copied over so that the blue vertical parallel lines are filled with the same seam part.

It does not really matter from where on the texture you copy the part that is to be used as a seam. To make the seam less noticable it is good to not use anything that would stand out too much on the seam itself. If I had chosen a section that was covered almost entirely by a single stone I would run into problems later. Likewise if I used almost only a dark part between stones it would make the seam noticable at the end.

The same process is then repeated with a different seam for the orange vertical lines and then for the blue and orange horizontal lines.

Step 9: Normal Map

The following steps vary a lot between different textures. For environment normal maps, I use the excellent program CrazyBump.

In order to "help" CrazyBump read some stones as higher up than the soil between them, I have one 50% opacity layer where I paint white on top to make a few chosen stones to come up more. Make sure that you duplicate the white on each repeating place on the seams so that the normal map will work properly as a tile texture too!

The Final Result