I've encounter an issue with using natural objects such as slate or marble as a seamless texture. When the object repeats it creates a very unnatural look within the model. My work around has been to draw each individual tile and alter the texture position. Usually when I do an area of 10ft x 10ft I've wasted an hour. The result looks great but it ridiculous that I have to do this every time. Is there a way that I can take the 10x10 area and make a texture out of that? In essence drawing my own texture. Any help would be great