Computer Graphics

Personally, I have no idea what kind of algorithms are used to make graphics look clean, neat, organized, you know -- realistic, which have by all means improved drastically in the last decade. But, I have dabbled in using some software to get textures to appear on meshes in games like Skyrim and Oblivion. 

Texture

The textures themselves in this game uses a .dds format (Direct Draw Surface) that some versions of Adobe Photoshop support or the freeware Paint.NET, 

Mesh

whereas the meshes .nif (Notation Interchange File) which contains the shape of the object using many, many triangles and probably a lot more information that I'm not aware of. These are somewhat editable with another freeware NifSkope.

Anyways, how some algorithms help obtain that realism is simply making it easier to create or make edits to images that later get wrapped around the mesh, or in whatever way an algorithm gets the image to appear on the mesh and look neat. Clipping Algorithms help in making things look neat and in doing so realistic, clipping being "Any procedure which identifies that portion of a picture which is either inside or outside a region" (Source)

References
http://en.wikipedia.org/wiki/Clipping_(computer_graphics)
http://www.fotocraft.org.uk/images/screamer4x4/Screamer4x4_03.jpg