How to Tile a texture Without Seams-
There are two key components to tiling a texture. The first is creating seamless boarders, the second part is eliminating noticeable repeats.

STEP 1: FIND A GOOD SOURCE PHOTO

A word of advice... if you ever need good source material for enviornement textures, do one of two things: 1) Take your digital camera to Home Depot! Bathrooms, Kitchens, Lawn and Garden... all right there, plus they usually have some good diffuse skylights which helps out when taking even lighting. So go one afternoon (never take source photos at night!!!!!) and take about 300 snapshots, and you'll have your own texture library for life. Or 2) Go get some excercise. If you live in the San Francisco Bay Area (and if you are taking my classes, you are), theres no better place to take it all in. Take a walk in the city, photograph the sidewalks, the buildings, the concrete, asphalt and metal. Or, head up to Marin County and go take a hike. The photos used in this demo were taken in Pt. Reyes National Seashore on the west coast of Marin Co.

So lets take this rock face photo and load it into Photoshop (We will be using version CS5 in this demo). You will notice a couple of things about it:

POSITIVES:
1-There are no heavy shadows
2-There is no color influence from the lighting
3-There are no visible specular highlights (try using a polarizer filter on your camera if you are seeing specularity thourgh the viewfinder)
4-The film back of the camera when the photo was taken was parallel to the surface, and the surface had no major curvature

NEGATIVES:
1-The photo is not square, or a power of two size, or 72dpi by default
2-There are white chalky splotches on the rockface which are irregular and noticeable
3-The grain of the rock has a horizontal cut in only one key area which will be noticeable

STEP 2: CROP THE IMAGE AND SET AS A SQUARE POWER OF TWO

Select the crop tool (shown below) and drag out a square selection (by holding down shift) and hit enter to complete the operation.

Next, go to Image-Image Size, set your file as a square power of two (256x256, 512x512....), in this case 2048x2048, and set your Resolution to 72dpi.

STEP 3: OFFSET

We then use the Filter-->Other--->Offset function. If we are usinga 2048sq texture as we are here, you can see that by offsetting the image at 1024x1024, the corners of the photo are now displayed together in the center. This will allow us to paint out the edge seams.

STEP 4: PAINT OUT THE SEAMS

You will notice that there are seams bisecting the image. We need to remove these. The easiest way to do this is to use the Content Aware Spot Healing Tool (but the Clone Stamp tool can be used as well for a more manual approach).

 

Select the Content Aware Spot Healing Tool (icon shown below), and just brush it over the area in one fluid stroke. This will darken the area effected (as shown below). It is best to do this in smaller chunks as your results will be more reliable. Doing the whole image's seams at once may cause undesireable results.

When you pick up your pen, Photoshop will take a second, then clarify your image. You should get something like this (AWESOME!):

 

STEP 5: REMOVE NOTICEABLE ITEMS

There are two ways to tackle this next task. In this rock scene file as I mentioned previously, there are these white streaks in the scene that will be very noticeable when tiled. We should remove those as well. One way is to continue using the Content Aware Spot Healing Brush (shown below), or to use the Clone Stamp tool manually (which is a little more old-school).

With a little bit of work, all the white is gone!

However, you can also use a content aware fill option. In the potential texture below, these two yellow flowers are ruining everything! Well, lets make a lasso selection around them first:

Then we can go to Edit-Fill and Use: Conent Aware. Hit Ok. BAM... filled with grass.

STEP 5: APPLY IN MAYA TO CHECK THE REPEAT

Add the image to a plane and adjust the U and V repeat values in the Place2dTexture node. Notice that even with all the work I've done on this grass, the slightly bare spots stand out when repeated only 3x3 times. Once you notice these repeats, just continue using the Content Aware tools to even out the texture. Reload in Maya until the image appears to continue seamlessly. Thats it!