Texture Mapping 101

Texture Mapping is taken for granted in the 21st century, but in the 1990's it was a revolutionary step, and activating it in a simulation placed huge demands on the graphics hardware and specifically the CPU's of the day.

Texture mapping objects

Polygons and planes
Texture mapping added
What it did allow developers to do was create the illusion of much more complexity in objects by simply mapping a 2 dimensional image to the surface. With clever use of shadows a 3 dimensional effect could be produced.
As you can see the effect worked best at certain viewing distances! The designers drew on their knowledge of impressionist art and the psychology of seeing.
The human brain is expert at blending discrete bits of visual information into a cohesive picture. We are 'pattern making' creatures.
As we can see in the following example the we can apparently see an urban landscape below.
Up close it disintegrates into discrete blocks.

Texture mapping terrain

Mapping objects in 2D with apparent shadows.
The same texture seen close up. There are a few polygons in the background which add scale and depth.