OK I'll try to keep this really basic;
Obviously you first get yourself a texture image - the diffuse map, once you have this, unless it comes as part of a pre-prepared texture you will have to do some photoshop work to get the maps you need to produce your final material. The first thing to do if you need a tiling (repeating) texture is to try and get rid of any big variations in the diffuse colour or areas which are a lot lighter or darker, as these will look really repeated on a large surface. A quick trick to try and even out an image is to use the following workflow;
duplicate image layer -
on background layer apply a 'blur average' -
on new top layer use 'high pass' filter set to about 80 -
set the layer type to 'linear light' and turn the opacity down to about 50%.
This won't always work and you may have to use some 'dodge' and 'burn' to try and even out the image more. You can see the difference just this quick fix makes on the below example.
Once you have your image tone and colours evened out you need to remove the joint lines that will be visible when the image repeats over a surface. To do this use the 'offset' tool and set both horizontal and vertical offsets to half the image height and width. This will give the joint lines in the centre of the image, as shown below. Now you need to get busy with copy & paste / clone tool / patch healing etc to get rid of these joint lines. You can find plenty of tutorials on how to do this if you google 'create tileable texture'.
OK... now you should have a diffuse map that you are happy with, all the other maps are created from this base diffuse map by firstly desaturating the image and then playing about with 'levels' until the image has much more contrast between white and black. You will also probably need to apply some blur to these adjusted maps as exaggerating the 'levels' will lead to the image becoming pixelated.
The only map you cannot make in this fashion is the normal map, which you will require a plugin for photoshop to achieve. This is, however, freely available from Nvidia's website
https://developer.nvidia.com/nvidia-tex ... -photoshop
I have run through a very basic example of a rock texture below showing the effect that each of the different maps have on the texture. For clarity I have omitted the diffuse map until the very last image, as it is easier to see what is happening on a plain colour. I have also exaggerated the glossiness etc for clarity.
Hope this is of some assistance! Good luck!
