View Full Version : Mapping Natural Land Forms

10-26-2009, 10:40 AM
With a little experience in Terrain Analysis and Photogrammetry I received from the Ohio State University, I thought I'd share some of the insight I've learned with others regarding how to make natural looking environments and land forms.

Impact of water erosion on hills and mountains.


This is a tree, correct? It is also the basis for how water creates channels we call rivers and tributaries. When creating a hill or mountain keep this 'tree concept' in mind and do an overlay onto your land mass. Where the tree trunk is thickest consider the land to be gouged out more and the water flowing slowly. Where the branches are thin consider this as a minor impact on the land as less water flows through these branches and therefore erodes less. The thicker part of the branch will dig itself into a hill mass... therefore if you have a waterfall it will be recessed into the hill (think of Niagara Falls and especially the river that flows away from the falls).

Basically water accumulates as it rains. As more water gets together it moves faster (it's heavier as a mass) and therefore erodes faster, in conjunction with the slope of the terrain. If a river exists on a flat plane, expect it to meander (not straight), and to provide very fertile soil perfect for farming (hence one would expect fields). It meanders because it is able to erode the sediments quit easily and therefore change direction. Rarely do flat land rivers flow straight unless bounded by boulders.

Also when making a river, remember that it sits in a basin, that is, river basins are typically wide and rock cliffs typically don't go straight down to the water's edge. There are exceptions, but typically one could walk along a rivers sides.

On the top of a hill, one would expect to find soil and therefore potentially a field. Along the slopes of a hill one would expect to find trees (wooded areas), rocks (exposed by erosion) and tributaries (as water can move faster on a slope). These tributaries are essentially mini valleys, but are sloped in relationship to the hill itself. When one creates path that intersects these tributaries they have a choice of

1) 'cutting' the ridges of the mini valleys (keeping the path more or less horizontal),
2) moving up and down over the tributary ridges, or
3) following the contours (keeping the path level).

Most natural paths, those created by animals or people, will have a combination of the 3 possibilities, as do roads. Basically 'paths' used by people will find the path of least resistance and therefore incorporate all 3 possibilities.

In this example by CryMod (http://crymod.com/thread.php?threadid=48588) user squeak_38 one can see the ridges and valleys cut through the rock of his islands, but there are no signs of tributaries. Still he shows a good grasp of the fundamentals of erosion.


But he is missing one very important ingredient. If all that rock was eroded thus creating the valleys, where did it go too? In other words, one would expect at the bottom of the valleys base, lower land forms and even signs of a river or dry rock beds which would cut itself down to the ocean. Also missing are signs of tributaries which would add a lot of natural detail to the land mass itself, although it looks like there might be a couple he's showing.

10-26-2009, 11:16 AM

Meandering River:

Road following contour:

2 Roads, one going over and one following contours:

Farm land on top of hill with woods on the steeper parts that are unfarmable, due to slope and rocky out-croppings: You'll also notice that where tributaries exist, there is a greater chance of exposed rocks and therefore are unfarmed and wooded.

10-26-2009, 11:25 AM
Types of ROCK

The way a land looks has to do with what rock is under the ground.

Granite is a very hard rock and hard to errode... expect to see more rounded tops, cracked sides and big boulders.

Sandstone is made up of compacted sand and therefore erodes easily. Here you will find jagged peaks, ridges and valleys with a lot of sediment at the base as shown here: You can also note color variations... red being clay deposits mixed with sand (ocean) deposits.

Marble is somewhere between granite and sandstone in it's characteristics: note how the ridges have their own ups and downs and aren't perfect.

10-26-2009, 11:32 AM

There are many types of valleys based on their location and the type of rock water runs through. Valleys create a wonderful experience where you can get a great vista while seeing what goals you might have to accomplish as a gamer.

Here are a few examples.

Flat Bottom Valley:

U-Shaped Valley:

10-26-2009, 11:42 AM
Stone Orientation:

There are a couple of basic orientations for stone... all stone (more or less) is the result of a layering of sediments. Over a lot of time, these layers are exposed as a result of erosion. Now either we see horizontal layers, or angled layers. Angled layers are a result of plate tectonics, that is continents pushing against on another causing the rock to be lifted vertically.

Here's an example of horizontal layering that has remained horizontal:

Here's an example of sloped horizontal layers... while you can't see the layers themselves, notice how the right side is smooth while the left side (exposed layers) are eroded. The variety of composition between hard and soft materials in the varying layers caused the left side to appear rough. Because it is rough, trees and brush have found a place to grow.