surfacemapguide.pdf

terragenSurface Map Guide

by Jo Meder

[email protected]://www.planetside.co.uk

Copyright © 2002 Jo Meder, Planetside SoftwareAll Rights Reserved

mailto:[email protected]

http://www.planetside.co.uk

Table of Contents

Introduction..............................................................................................................................Page 3

1 : How Terragen’s Surface Map System Works.....................................................................Page 4

2 : Introducing the Parent / Child Metaphor............................................................................ Page 5

3 : How a Surface Map is Displayed and Manipulated...........................................................Page 6

4 : Child Layers in Depth.........................................................................................................Page 11

5 : An Introduction to the Surface Layer Editor.......................................................................Page 17

6 : The Surface Layer Editor in Detail - The Surface Tabs.......................................................3

7 : The Surface Layer Editor in Detail - The Distribution Tabs...............................................Page 26

8 : Conclusion...........................................................................................................................Page 35

Page 2

Introduction

Surface maps are what bring your Terragen terrains to life. However, a lot of people seem to have trouble getting started with them. The purpose of this guide is to explain how the surface map system works, and how the settings in the Surface Layer editor affect the final terrain. It is not intended to be a guide to actually creating surface maps, but rather to give you a better understanding of how everything works so that you find it easier to create surface maps yourself.

Many of the example images used in this guide are a bit too small to see differences in settings without close scrutiny. Larger images will be made available on the web in due course, check back at the Terragen website <http://www.planetside.co.uk/terragen/> for news about when they become available.

Many thanks to those who helped proofread this guide, particularly Mark Doughty and Oshyan Greene who provided long lists of corrections.

http://www.planetside.co.uk/terragen/

1 : How Terragen’s Surface Map System Works

Terragen uses what is known as a procedural surface mapping, or texturing, system. Unless noted, I use the terms “texturing” and “surface mapping” interchangeably. “Procedural” means that the surface colour and texture ( I mean texture as in the “feel” of surfaces, whether they’re smooth or rough for example ) is calculated on the fly as rendering happens, and it doesn’t use pre-existing images, which is a common way of doing things in other 3D applications. Essentially, it does a whole lot of maths to generate the surface map. There are several advantages to the procedural approach. The most important one is that detail is potentially unlimited, you can zoom right in close or zoom out a long way and the surface map will still look good. If you were using a pre-existing image ( such as a JPEG or BMP file ) to give the surface its appearance, as you moved in closer to the surface you could start to see blurry or blocky artefacts. If you have played 3D computer games, such as those from the Quake series or any number of other PC and console games, you have probably noticed this effect - a lot of the time you just need to walk up close to a wall or other object. This sort of thing isn’t a problem with procedural surface maps.

The other main advantage of procedural surface maps is that they can usually be stored very efficiently. If you wanted to store images with enough detail to fully texture a Terragen terrain to an acceptable level of detail you could potentially be looking at needing many, many gigabytes of disk space. A procedural Terragen surface map, even a very complicated one, would rarely take up more than a few hundred kilobytes of disk space. This is because each part of the surface map is stored as just a few numbers, and Terragen is able to recreate the surface map from those numbers when you render an image.

There is a trade off here, as is often the case with computer programming. Procedural surface mapping is generally more processor intensive ( it makes the computer’s main processor workharder ) during rendering, but that’s a small price to pay when you realise that getting the same results using images could be impossible in practical terms. If you look back at what I said about the potential blockiness and blurriness of using images and how you can often see this in computer games, you may be wondering why games don’t use procedural textures instead. One of the reasons is that all but the simplest procedural textures are generally too processor intensive to be used in situations like games that need to draw many frames per second. As computers get faster and the graphics processors on 3D cards become more advanced, you should see procedural surface mapping being used much more in interactive applications such as games.

Of course images are also able to portray things that it would be impractical to use procedural textures for, such as a picture of your father. As you might actually want to have a picture of your father on the side of a hill in a Terragen rendering one day, you can use plugins to extend Terragen’s surface mapping capabilities. For example, a plugin could be used to place the picture of your father in the surface map.

2 : Introducing the Parent / Child Metaphor

The fundamental concept to keep in mind when you are working with surface maps is that they are hierarchic, based on a parent-child metaphor. Keeping the parent-child idea in mind helps to give you an idea of how the layers interact. A child layer can only appear where its parent does. This means that in the rendered image the child layer can only appear on parts of the surface where the parent would be rendered if it had no children, regardless of the specific distribution settings of the child. The child layer still respects the distribution settings you give it, but it can only appear where its parent's distribution allows it to. The parent layer controls where it’s children can appear. ( Fig 1 ) illustrates these concepts.

Children can only appear where their parents also appear

Parents control where their children can go

Fig 1

3 : How a Surface Map is Displayed and Manipulated

The heart of the surface mapping system is the Surface Map area of the Landscape window. This is where you create and arrange the layers that go into the surface map. As you can see, there is a list box and a number of buttons. There is one fundamental thing to remember about this list box :

The surface layers are listed upside down

To expand on that further, layers that are further down the list cover those that are further up the list. The layer at the bottom of the list covers every other layer. Here’s a diagram to show you what I mean ( Fig 2 ) :

Fig 2

When you start Terragen there is only one layer in the list ( Fig 3 ). This is what you might call the base layer, it covers the entire terrain. It is the ultimate parent of every other layer in the surface map. You can only change a few of the settings relating to this layer, there are no distribution settings ( which will be explained later ) for it because it always covers the entire terrain. You can not delete it. To make the surface map more interesting, you need to add some more layers. This is what the “Add Child” and “Add” buttons beneath the list are for. In the case of the base layer, you can only add children to it, so if you select the layer only the “Add Child” button becomes active. If you then click the button, you will see a new surface layer appear in the list ( Fig 4 ).

Fig 3 Fig 4

This layer is a child of the base layer. As such, it can only appear in areas of the terrain that its parent covers. In this case the parent ( the base layer ) always appears everywhere, so it follows that this new layer can potentially cover any part of the terrain.

You will notice it is now possible to click on the minus sign next to the base layer name ( on Windows ) or the disclosure triangle ( on the Mac ) and the list will collapse so only the base layer’s name is shown. If you click on it again, the list will expand and the new layer name will show again. Apart from being a handy organisational tool once the surface map becomes more complex, this should help to further demonstrate the hierarchical nature of the surface map. If a surface layer doesn’t have a plus/minus sign ( Windows ) or disclosure triangle ( Mac ) next to it, then that layer has no child layers.

All layers that share the same level of indentation from the side of the list box, and which have the same parent, are siblings. In ( Fig 5 ), Parent A and Parent B are siblings, they share the same level of indentation. Child A and Child B are also siblings, as they share the same parent ( Parent A ) and the same level of indentation. However, although Child C shares the same level of indentation with Child A and B, it is not a sibling of Child A and B as it has a different parent ( Parent B ).

Fig 5

To add a sibling to a layer, you can either select the surface layer and click the “Add” button, or you can select the layer’s parent and click the “Add Child” button. Both achieve the same thing. If you happen to be using Terragen while reading this, try it out. To clarify things a little, you should change the names of the surfaces from the default. Select the first layer we created and then click the “Edit” button. This opens the Surface Layer editor. This will be explained in detail later, but for now just change the name using the text field at the top of the window, call it “Layer 1” or similar. Now go back to the Landscape window ( you don’t need to close the Surface Layer editor ) and select the second layer we created. Switch back to the editor and change the name of this layer to “Layer 2” or similar.

Now, you should remember from earlier that the surface layers are listed upside down, and it’s now possible to better illustrate what this means. The diagram below ( Fig 6 ) shows a stylised view of how the surface map will look when rendered. The base layer is yellow, Layer 1 is the red dots and Layer 2 is the blue triangles. As you can see, the blue triangles cover the red circles in places, and both cover the yellow base.

Fig 6

Layer 2 is furthest down the list so, in upside down fashion, it is on top of all of its other sibling layers in the list.

It is possible to rearrange the order in which sibling layers cover each other. If we want the blue triangles of Layer 1 to cover the red dots of Layer 2 then we need to move Layer 1 further down the list. This is what the “Move Up” and “Move Down” buttons at the right of the list are for ( Fig 7 ).

Fig 7

The “ Move Up” button moves a layer up the list, but only as far as its parent. You cannot move a child up past its parent. The “Move Down” button moves a layer down the list, but it will not move so that it becomes a child of one of its siblings. Essentially, you can only move a layer amongst its siblings. Note that when you move a layer, all its children follow along with it. ( Fig 8 ) shows a surface map before and after rearranging the layers. On the left ( Fig 8a ) is the original arrangement. On the right ( Fig 8b ) you can see the order of layers after the Parent A layer has been selected and the “Move Down” button pressed. As you can see, the child layers of the Parent A layer, Child A and Child B, have also moved along with their parent layer.

Fig 8a Fig 8b

Again, keep in mind the idea that the layer list is shown upside down. Moving a layer with the “Move Up” button actually moves it further down the rendered layer stack, and moving it with “Move Down” button moves if further up the rendered layer stack.

The last button to discuss which affects the layer list is the “Remove” button. As you might imagine, this removes the selected layer from the list. If the layer you remove has any child layers, then they are also removed from the list. You cannot remove the base layer, it is always present.

The grey square on the right of the layer list is intended to show a preview of the surface map, however this has not yet been implemented.

4 : Child Layers in Depth

Child layers were introduced in the preceding segment, and here they’ll be discussed in more depth. You could make a surface map which consisted entirely of siblings which were children of the base layer, but for greater control and subtlety you can create child layers of those layers.

One of the most important parts of the parent/child metaphor is that children can only appear where their parents also appear. The following figure ( Fig 9 ) illustrates this . Again we have two layers, not counting the base layer which is yellow. Layer 1 is the red dots and Layer 2 is the blue triangles. This time however, Layer 2 has a child layer, and this child layer is shown as green stripes. As you can see, the green stripes of the child layer only show in the blue triangles of Layer 2. If we change the order of the layers, using the “Up” button, we can see that Layer 2 is now below Layer 1 in the final image ( Fig 9b ), and that the green stripes of the child layer still only appear in the blue triangles of Layer 2. When the order of the layers is changed, the child layers follow along with the parent. As Layer 2’s child layer only shows where Layer 2 appears, you can see that the red dots of Layer 1 cover both.

Fig 9a Fig 9b

Terragen has a number of ways of restricting where layers appear. This is known as controlling their distribution. These will be discussed in greater depth when the Surface Layer Editor is discussed, but I’ll introduce two main ways of controlling the distribution now. One way is controlling where the surface appears based on the slope of the underlying terrain. This is useful if you only want a surface layer to appear on parts of the terrain that are fairly flat, for example you wouldn’t want a grassy looking layer to appear on a vertical rock face. The other way of controlling the distribution is based on height. You can make a layer only appear above a certain height, below a certain height or between two particular heights. An example of this might be snow which you only want to appear above a certain height up a mountain. To further illustrate the way in which child layers are restricted to the areas of the terrain that their parents also cover, two real world examples with actual Terragen renderings will be discussed.

The first example will be a grassy surface. The terrain is pretty hilly, and we only want the grass to appear on the flatter areas of the terrain. As a bit of an aside, an Interesting Fact From Nature is that grass generally tends to only grow on slopes which are shallower than 45 degrees. ( Fig 10 ) shows what our surface map looks like in the layer list.

Fig 10

The base layer is coloured grey, the layer called “Dark Grass” is dark green, and the layer called “Light Grass” is light green. The distribution of the “Dark Grass” layer has been changed so that it only covers parts of the terrain which have a slope of less than around 45 degrees. The “Light Grass” layer is a child of the “Dark Grass” layer, as you should see. The distribution of the “Light Grass” layer has been changed so that it has no slope restrictions, that is it would cover the entire terrain if it wasn’t limited by its parent “Dark Grass” layer.

The following figures show the terrain rendered with only the base layer ( Fig 11 ), the terrain with the “Dark Grass” layer added ( Fig 12 ) and the terrain with the “Light Grass” layer added ( Fig 13 ). Please note that it is not yet possible to turn individual layers on and off like this in Terragen, this is done in a slightly more complicated way for the purposes of these examples. ( Fig 14 ) is a close up which shows you that the light green of the “Light Grass” layer only goes to the edge of its dark green parent layer, and not beyond.

Fig 11 Fig 12

Fig 13 Fig 14

Now, if the “Light Grass” layer were not a child layer of “Dark Grass”, but rather a sibling to it, then the results would be quite different. Using the same distribution settings as before, but with the “Light Grass” layer as a sibling of the “Dark Grass” layer, ( Fig 15 ) shows what the final image would look like. ( Fig 16 ) shows the close up again. As you can see, the light green colour of the “Light Grass” layer covers parts of the grey base layer as well, whereas in ( Fig 13 ) the “Light Grass” layer only showed up where the “Dark Grass” layer did. Again, child layers are restricted so they can only appear where their parent does.

Fig 15 Fig 16

The second example uses a beach as an illustration. A very weak illustration, but you should get the idea. In this example the base layer is coloured light green, the layer called “Beach” is a sand colour, and the layer called “Seaweed” is dark green. The distribution of the “Beach” layer has been changed so that it doesn’t appear above a certain height on the terrain, to give the appearance of a beach. The distribution settings of the “Seaweed” layer have been changed so there are no altitude restrictions, if it weren’t being controlled by the parent “Beach” layer then it would cover the whole terrain. ( Fig 16 ) shows the surface layer list.

Fig 16

The following figures show the terrain rendered with only the base layer ( Fig 17 ), the terrain with the “Beach” layer added ( Fig 18 ) and the terrain with the “Seaweed” layer added ( Fig 19 ). ( Fig 20 ) shows a close up which shows you that the dark green of the “Seaweed” layer only goes to the edge of its beige parent layer, and not beyond.

Fig 17 Fig 18

Fig 19 Fig 20

Once more, ( Fig 21 ) shows what the results would be if the “Seaweed” layer were a sibling of the “Beach” layer, and not a child. ( Fig 22 ) is a closeup. The dark green of the “Seaweed” layer covers the entire terrain, and it’s no longer restricted to just the area the “Beach” layer covers.

Fig 21 Fig 22

The two previous examples were very similar, but hopefully they serve to illustrate the point that child layers can only appear where their parents do, and that point is firmly driven home. With that in mind, you should find it much easier to create Terragen surface maps.

5 : An Introduction to the Surface Layer Editor

The last button in the Surface Map area of the Landscape window that we have not touched on is the “Edit…” button. Clicking this button opens the Surface Layer Editor for the selected layer, and with that you will find the part of Terragen that really gives you control over the appearance of your surface maps ( Fig 23 ). The Surface Layer Editor ( hereafter referred to as the Editor ) allows you to control many aspects of a surface layer, from its colour, to its roughness and all the way through to its distribution, or rather, what parts of the terrain it covers. The Editor also gives you access to various types of plugins, the effects of which are largely only limited by the imaginations of plugin writers. This chapter will introduce you to the various parts of the Editor, and what they do.

Fig 23

Right at the top of the Editor, you’ll find a text field ( Fig 24 ) where you can change the name of the surface layer you are currently editing. The length of the name is currently limited to 255 characters, but in practice you shouldn’t find this to be a problem. There are also two buttons, “Open Layer...”

and “Save Layer...”. These buttons let you insert the layers from another surface map file into the current surface map and save the current layer ( along with its children ) as a new surface map file, respectively. In the Mac version these two buttons have been replaced with a single button in the top right which pops up a menu to let you perform these operations.

Fig 24

( Fig 25 ) shows you the effects of inserting the layers from one surface map file into another, using the “Open Layer...” button. ( Fig 25a ) shows the original surface map. ( Fig 25b ) shows you what the surface map we’re going to insert looks like, and ( Fig 25c ) shows you what the original surface map looks like once the second surface map has been inserted into the Layer 2 layer with the “Open Layer...” button. This can be a handy way of utilising prefabricated surface maps.

Fig 25a Fig 25b

Fig 25c

As you can see, Layer 2 is now called “Dark Rock” and has become, in effect, the same as the second surface map, with all its children. As mentioned above, you can utilise premade surface maps this way. You might have a snow surface map set up, and whenever you need a snowy area in a surface map you could insert that snow surface map into it. The inserted surface map becomes part of the surface map you’re inserting it into, the file you’re taking it from is not affected.

The next main part of the Editor is the upper set of tab panels ( Fig 26 ). This set of tab panels is divided into two parts, the “Base Surface” panel and the “Child Surfaces” panel. The “Base Surface” panel ( shown in ( Fig 26 ) ) provides controls that affect the appearance of the surface layer, its colour and its bumpiness or roughness. As you can see, there is a graphic preview to give you some idea of the appearance of the layer. This panel also allows you to access plugins which let you change the colouring of the surface layer. Instead of just a solid colour, a plugin could replace it with a picture or change the colour values depending on height, as an example.

Fig 26

The other tab, “Children Surfaces” ( Fig 27 ), gives an opportunity for plugins to modify the way the child surfaces, if any, of the layer you are editing behave. In the version of Terragen released at the time of writing ( v0.8.44 ), you cannot change the “Distribution of children” setting from “Normal”, and cannot use child surface plugins. Therefore, this panel will not be discussed further at the present time.

Fig 27

The last main area of the Editor is the lower set of tab panels, which make up the largest part of the window ( Fig 28 ). Again, this set of tab panels has two tabs, “Distribution Presets” and “Advanced Distribution”. All of the controls on both tab panels concern themselves with the distribution of the surface layer, or to put it another way, what parts of the terrain the surface layer covers. If you happen to be editing the base surface layer, none of the settings here are available to you - as discussed previously you cannot change the distribution settings of the base surface layer, it always covers the entire terrain.

The first tab panel, “Distribution Presets” ( Fig 28 ), is not much use at this time. As the name suggests, at some stage this tab will allow you to choose preset distribution settings, such as only allowing the surface layer to cover gently sloped areas of the terrain. At the time of writing ( the current version of Terragen is v0.8.44 ) none of these presets have been implemented.

Fig 28

The second tab panel, “Advanced Distribution” ( Fig 29 ), is where things really happen. Please don’t be put off by the “Advanced” part, the settings here are largely very straightforward, as you will see when they’re explained in greater depth later. Although possibly a lot of people are initially put off by all the settings here, once you know what they do it should all become much less intimidating. The various settings allow you to control things such as how much of the terrain the surface layer covers, whether it should appear above or below a certain height, and whether it should appear on steeply or gently sloped parts of the terrain. You can also access plugins which control the distribution of the surface layer here, for example a plugin might let you restrict a surface layer to appear only within a circle or other shape, or a plugin might give the effect of a dirt track.

Fig 29

6 : The Surface Layer Editor in Detail - The Surface Tabs

At the top of the window are the surface tab panels, as mentioned above. The first tab panel, “Base Surface” controls the basic appearance of the surface. The second tab panel, “Children Surfaces” allows you to control how the surface layer you’re editing interacts with its child layers. To start at the very beginning, the “Base Surface” tab panel ( Fig 30 ) will now be discussed.

Fig 30

Item 1 : The surface previewThe purpose of this preview is to give an idea of what the surface layer looks like, and it shows the colour and bumpiness. Of all the controls in this tab panel only the Bumpiness slider ( Item 2 ), Reset Bumps button ( Item 3 ) and Colour button ( Item 6 ) have any noticeable effect on the preview.

Item 2 : The Bumpiness sliderThis controls the bumpiness or roughness of the surface layer. After adjusting it, the surface preview will update to show the effect of this setting. Move the slider to the left for a smoother surface, move it to the right for a rougher surface.

Item 3 : The Reset Bumps buttonClicking this button resets the internal settings of the bump texture, and changes its appearance somewhat, but it has no effect on the other settings in the tab panel. This isn’t especially useful, but feel free to experiment with it if you wish.

Item 4 : The T buttonsWhat I’ll call the T buttons, for obvious reasons, are all disabled at the moment, and don’t do anything. The functionality they were intended to provide hasn’t been implemented yet. In a future version of Terragen, they may become active, but for now you can just ignore them.

Item 5 : The Mimic Terrain sliderThis setting controls how closely the surface layer mimics the underlying terrain. Basically, this setting modifies the bumpiness setting of the surface layer. At a high setting, on steeper parts of the terrain the surface layer will be bumpier, and in flatter areas it will be smoother. Move the slider to the right for higher values. At the lowest setting, all the way to the left, the bumpiness will be the same across the entire terrain. This is quite a subtle effect, some examples are shown below to illustrate it ( Fig 31 ).

Fig 31a Fig 31b

Fig 31c Fig 31d

( Fig 31a ) shows no mimic ( slider all the way to the left ), ( Fig 31b ) shows a half mimic setting,( Fig 31c ) shows the default mimic setting and ( Fig 31d ) shows the highest mimic setting ( slider all the way to the right ).

Item 6 : The Colour buttonAs you may have guessed, clicking this button opens the Colour Picker, allowing you to specify a colour for this surface layer. After you choose a new colour the surface preview will update to show

the new colour.

Item 7 : The Tex buttonThis is the Tex button, Tex being short for Texture. Clicking it opens a plugin selection dialog, which lets you choose plugins of the RGB Texture type. These plugins have access to the colour of the surface layer during rendering, and can modify it in pretty much any way you can think of. One example of an RGB Texture plugin is an image overlay plugin. This lets you select an image which is then drawn on the surface during rendering, see ( Fig 32 ) for an example. In this case, the red area and the white text are from a BMP image that was overlaid on the surface layer, and the beige areas are the normal Terragen surface map. This was done with the SOPack plugin, see the Resources page of the Terragen website if you are interested in obtaining it.

Fig 32

Note that the effects of any plugins you might choose will not show in the surface layer preview.

Item 8 : The Shine buttonCurrently this button is disabled as the functionality it’s intended to allow you to control hasn’t been implemented yet. The intention of this button is to allow you to control the shininess, also known as specularity, of the surface layer. For example, you could use it to make a surface layer appear metallic, or to make a surface look as though it were wet.

Item 9 : The Luminous buttonAgain, this button is disabled because what it’s supposed to do hasn’t been implemented yet. The intention of this button is to let you make a surface layer appear as if it were glowing. You might use this to give the effect of a luminous mould on a cliff or similar.

7 : The Surface Layer Editor in Detail - The Distribution Tabs

The lower, and larger, set of tab panels control the distribution of the surface layer, or which parts of the terrain it covers. Although there are two tab panels, the first, called “Distribution Presets”, will be ignored here, as it has no controls which have been implemented. As mentioned previously, the intention is to have simple presets, such as “the surface layer only appears on steep areas of the terrain”, which can be chosen from this tab panel. The second tab panel, “Advanced Distribution” ( Fig 33 ), is where everything happens, and will now be explained in detail.

As mentioned earlier on, do not be put off by the fact that this tab panel is called “Advanced Distribution”. All of the settings here, with one notable exception, are straightforward and the following explanations will hopefully show that.

Fig 33

Item 1 : The distribution previewAlthough it is a bit small and might look somewhat odd to you, the distribution preview is in fact an accurate preview of the distribution of the surface layer over the terrain, based on the settings in this tab panel. White shows areas that the surface layer covers, black shows areas it doesn’t and intermediate grey shades give you an idea of the intensity of the surface layer in that area. Essentially, the lighter the shade the more strongly the surface layer shows.

Note that this preview does not show the influence the parent layer might have over this layer. You

should be well aware by now that the parent layer restricts its child layers so they can potentially appear only where the parent appears. This preview does not show that, rather it shows the distribution of the surface layer across the whole surface as if it were unrestricted by its parent. Although this may seem like a bit of a shortcoming, you shouldn’t find it so in practice.

The distribution preview updates in response to changes to various settings in this tab panel.

Item 2 : The Coverage sliderThis setting controls something other than what you might suppose. Rather than control the amount of the terrain a surface layer covers, it actually controls the intensity of the surface layer colour. You might think of it as a kind of blending or fade control. Shown below are some examples which show the Coverage set to the lower end of the scale ( with the slider to the left ) ( Fig 34a ), the Coverage set to about 1/3 value ( Fig 34b ), the Coverage set to about 2/3 value ( Fig 34c ) and the coverage set to a high value ( Fig 34d ) ( all the way to the the right ). The layer we’re interested in is coloured red, and the underlying layer is beige. As you can see, as the Coverage setting increases, the surface colour becomes more intense, and less of the underlying colour shows through. The red colour does appear to cover more as the Coverage value increases, but really it is intensifying the colour in areas it was already covering, if only very faintly.

Fig34a Fig 34b

Fig34c Fig 34d

Item 3 : The Fractal Noise sliderThis slider controls what you might actually think of as coverage. It controls how “noisy” the surface layer is. At higher settings, with the slider toward the right, the surface layer will generally have a patchier appearance.

In truth, it’s not really as cut and dried as the descriptions for the Coverage and Fractal Noise settings might have you believe. To get the effect you want, you will probably have to play with both settings, they really work in conjunction with each other. Rather than have examples of their interaction here, it would be best if you try it out for yourself. Start up Terragen and set the camera so it’s pretty high above the terrain. Don’t worry about generating a terrain, Terragen’s default flat one will do. Now go to the Surface Map area and add a child layer to the default layer. Select the child layer, open the Surface Map Editor and give the child a fairly lurid colour, such as pure red or magenta. Now change the Coverage and Fractal Noise settings and do some preview renders ( turn off the sky to speed things up ). Try things like having the Coverage set to its lowest value and the Fractal Noise set to its highest value and vice versa. Try both at their highest or lowest values. Try intermediate values. You should quickly see how the settings effect the surface layer, much more quickly than I can explain it.

Item 4 : The Scale sliderThe Scale setting controls how the bumpiness setting of a layer is affected by the bumpiness of underlying layers. Probably the best way to describe this is with an illustration, Figure ( Fig 35 ), which is somewhat exaggerated.

Fig 35a Fig 35b

In the illustration, the red area shows the layer currently being edited, which has a low bumpiness value, and the green area indicates the underlying layers. ( Fig 35a ) shows a low scale setting ( with the Scale slider to the left ) and ( Fig 35b ) shows a high scale setting ( with the Scale slider to the right ).

As you can see, in ( Fig 35a ) with the low Scale setting, the red layer conforms closely to the bumpiness of the underlying layers. In ( Fig 35b ), with the Scale setting on a high value, the red layer is much less influenced by the bumpiness of the underlying layers. In this case the red layer has a low bumpiness setting, as mentioned above, and this means the resulting surface is very smooth. If the bumpiness of the red layer were higher then the surface would be a lot rougher, but the point is that it would be much less influenced by the bumpiness of the underlying layers - having a smooth surface just helps to clarify the effects.

A good real world metaphor to describe the effect of the scale setting, for those from snowy climes anyway, is to think of the difference between a light dusting of snow and a heavy fall on a lumpy surface. Think of the red layer as the snow and the green layer as the lumpy surface it’s falling on. If you wanted to show a light dusting of snow in Terragen, where the snow covers the surface but there is not enough falling to change its contours, you would use a low scale setting. If you wanted to show a heavy fall of snow, where there is so much snow that the contours of the underlying surface have been obscured and all you can see is the surface of the snow as it has fallen, then you’d use a high Scale value, with the slider all the way to the right. Below are a couple of renderings from Terragen illustrating this metaphor. The image on the left ( Fig 36a ) shows the snowy layer with a low scale Setting, and the image on the right ( Fig 36b ) shows the snowy layer with a high Scale setting. As

you can see, in the image on the right the snowy layer has smoothed out the bumpiness of the underlying surface layers, much like a heavy fall of snow would.

Fig 36a Fig 36b

Item 5 : The T buttonsAs discussed in the “Base Surface” tab panel description, these T buttons are all currently disabled. The functionality they are intended to expose has not yet been implemented.

Item 6 : The Randomise buttonThis button does not do anything at the time of writing.

Item 7 : The Tex buttonLike the Tex button in the “Base Surface” tab panel, this Tex button also allows access to plugins. Although these plugins are also of the RGB Texture type, this time they control the distribution of the surface layer rather than the colour. As a simple example, a plugin of this type could restrict the surface layer so it only appeared inside a circle or only over one half of the terrain. When you have chosen a plugin of this type and returned to the Surface Layer Editor, the distribution preview will update to show you the effect it has.

Altitude Constraints groupThese settings let you control where the surface layer appears based on height. They should be reasonably self explanatory. You can set the controls so that the surface layer only appears below a certain height, for example the surface layer might represent a beach that you only want to extend a certain distance above the water level. You can set the controls so that the surface layer only appears above a certain height. A good example of this is a snow layer that you only want to cover the upper portion of a mountain. You can set the controls so that the layer only appears between two particular heights, which you might do to put a band of contrasting colour across a cliff. Of course you can also turn the altitude constraints off altogether, so they play no part in deciding where a surface layer appears. Note that the distribution preview will update to reflect changes you make to

these settings.

Due to the parent-child metaphor, meaning that children can only appear where their parents can appear, if you have set up altitude constraints for this layer’s parent layer you don’t have to adjust this layer’s altitude constraints to match - this layer can never appear outside its parent layer’s constraints. However, you can still set this layer’s constraints to be different to those of its parent if you so wish. Bear in mind that the effective range of possible values for the constraints is limited to that of the parent layer. If, for example, the parent layer’s maximum altitude is 10 units and you set this layer’s maximum altitude to 12 units, this layer is still limited to the 10 unit maximum of its parent.

Item 8 : The altitude previewThis is the altitude preview, which gives a rough idea of the range of heights the surface layer covers. The white line ( red on the Mac ) shows the area covered by the layer. This display is proportional. No matter what the minimum and maximum altitudes of the terrain, this preview still shows what proportion of that is covered by the surface layer. The preview updates when you make changes to several of the altitude constraint settings.

Item 9 : The Max Altitude checkboxChecking this checkbox turns on the maximum altitude constraint. With this on, no part of the surface map will appear above the height specified in the text field to the right ( Item 10 ). The distribution preview and the altitude preview will update to reflect this.

Item 10 : The Max Altitude text fieldWhen the Max Altitude checkbox is checked, the value in this text field controls the maximum height that the surface layer can reach to. Note that because this setting is an absolute height, not a percentage, if you use this surface map on a terrain which is quite different to the original, you may not get the results you expect. The distribution preview and the altitude preview will update to reflect changes you make to this setting.

Item 11 : The Min Altitude checkboxChecking this checkbox turns on the minimum altitude constraint. With this on, no part of the surface map will appear below the height specified in the text field to the right ( Item 12 ). The distribution preview and the altitude preview will update to reflect this.

Item 12 : The Min Altitude text fieldWhen the Min Altitude checkbox is checked, the value in this text field controls the lowest point that the surface layer will appear. As before, this setting is an absolute height, not a percentage. If you use this surface map on a terrain which is quite different to the original, you may not get the results you expect. The distribution preview and the altitude preview will update to reflect changes you make to this setting.

Item 13 : The Altitude Fuzzy slidersThe Fuzzy sliders control the abruptness of the transition between the area under the control of their respective constraint and the rest of the terrain. Here’s an example where the Max Altitude constraint is turned on, lets say with a setting of 10 units. All the area of the terrain below 10 units in height will be covered by the surface map, areas of the terrain higher than 10 units will not be covered. If the Fuzzy slider is all the way to sharp side ( the left ), then the transition between the two areas will be very crisp, abrupt and sharp. As you move the Fuzzy slider to the fuzzy end ( the right ), the transition between the two areas will become progressively softer and blurrier. If you move the slider all the way to the fuzzy end, the transition will be so blurred that you may not be able to see the surface layer at all, or at least it will only be a faint tint. This is a very powerful control. The images below ( Fig 37 ), which show a red surface layer using a maximum altitude constraint, illustrate the effect of the Fuzzy slider, starting at the sharp side and moving toward the fuzzy side. As you can see in the final image, where the slider is hard up against the fuzzy end, you can see very little of the red surface layer at all. The distribution preview will update to reflect changes made to the Fuzzy sliders.

Fig 37

Slope Constraints groupThese settings allow you to control where the surface layer appears according to the slope of the underlying terrain. Again, these controls should be pretty self explanatory. You can set the controls so that a surface layer only appears on areas of the terrain that are relatively flat. An example of this might be a grass surface layer. Due to the fact that grass generally only grows on areas that have less than 45 degrees of slope, you could restrict the surface layer so it only appears on parts of the terrain that might be more gently sloped than that. You can set the controls so the surface layer only appears on parts of the terrain that are nearly vertical. This could be useful where you wanted to apply a surface layer to cliffs but no other part of the terrain. You can set the controls so that a surface layer only appears on parts of the terrain that are steeper than a certain angle and shallower than a certain angle. Of course, you can also turn the constraints off so the slope has no effect on where the surface layer appears.

Due to the parent-child metaphor used for surface maps, if you have set up the slope constraints of the parent layer, you don’t need to do anything else if you want the child layers to match those constraints. You only need to change them if you want the child layers to have different slope constraints. Bear in mind that the range of effective slope constraints is limited by the settings of the parent layer, for example if the maximum slope of the parent layer is set so it only appears on parts of the terrain shallower than 45 degrees, and you change the maximum slope constraint of a child layer to be more like 80 degrees, that layer will still only appear in areas shallower than 45 degrees. It is still limited by its parent’s constraints.

Item 14 : The slope previewThe slope preview gives an idea of the range of angles of the slopes in the terrain that the surface layer covers. The bottom of the preview is at 0 degrees, or flat, and the top of the preview shows 90 degrees, or vertical. As you might imagine, a 45 degree slope is halfway along the curve of the preview. The white line ( red on the Mac ) shows the range of the slope constraints. This preview updates when you make changes to some of the slope constraint settings.

Item 15 : The Max Slope checkboxThis checkbox lets you turn the maximum slope constraint on or off. When it’s turned on, the surface layer will only appear on areas of the terrain that are more gently sloped than the maximum slope you’ve chosen with the Max Slope slider ( Item 16 ). The distribution preview and the slope preview will update when you change this setting.

Item 16 : The Max Slope sliderThis slider lets you control the angle where the maximum slope constraint takes effect. Although there’s no way to set this angle numerically, looking at the slope preview ( Item 14 ) should give you a good idea of the angle. The angle varies from 0 degrees at the left end of the slider to 90 degrees at the right end. Both the distribution preview and the slope preview update to reflect changes to this setting.

Item 17 : The Min Slope checkboxChecking this checkbox will turn on the minimum slope constraint. When this constraint is turned on, the surface layer will only appear on parts of the terrain that are steeper than the angle specified by the Min Slope slider ( Item 18 ). The distribution preview and slope preview will update to show you the effects of changes to this setting.

Item 18 : The Min Slope slider This slider controls the angle where the minimum slope constraint takes effect. Although there isn’t a way to set this angle numerically, the slope preview ( Item 14 ) should give you a good idea of it. The slider values range from 0 degrees at the left end to 90 degrees at the right. The distribution preview and slope preview update to reflect changes to this setting.

Item 19 : The Slope Fuzzy slidersThese sliders do exactly the same thing as the Altitude Fuzzy sliders ( Item 13 ). For more detail, please look to that description. Of course, instead of modifying the crispness of the altitude constraint transitions, these sliders control the crispness of the slope constraint transitions. The slope preview will update to reflect changes to these settings.

That then is all the surface layer controls. As you can see, it isn’t really that complicated, and allows a pretty good degree of flexibility.

8 : Conclusion

Although creating surface maps with Terragen can seem a bit confusing at first, hopefully it is all a little clearer now. To sum up, here are the main things you need to keep in mind :

- The Surface Layer list, where you organise the surface layers, displays the layers as if they were upside down. The Base Surface layer is below all other layers, and it always covers the entire terrain. Layers that are further down the list will cover their sibling and parent layers which are further up the list.

- Terragen uses a parent-child hierarchy to organise the surface layers. A child layer can only appear on the surface where its parent layer can also appear. Parents control their children.

- You do not need to set up the constraints of a child layer to match those of its parent. As a child layer can only appear where its parent can also appear, the child automatically inherits the same constraints that its parent has. That’s not to say that if, for example, a parent’s maximum slope constraint is set to 45 degrees then the maximum slope constraint for the child is also set to 45 degrees. You can set the child’s constraints to whatever you like, but the maximum and/or minimum constraints will always be dictated by the parent.

- Don’t be put off by the Advanced Distribution tab ! All the settings here are generally straightforward and if you experiment with the settings a bit, you should soon become familiar with what they do.

Although the intention of this guide is not to tell you how to create a surface map, there are a number of tutorials which deal with that, here are some tips which might help you out :

- It can help to make a surface some particularly lurid colour, such as bright pink or turquoise, while you are initially adjusting a surface layer’s settings. This makes the surface layer stand out from the other layers and you can easily see the effects your changes are having. When you are satisfied with the distribution etc. of the layer, then change its colour to the one you want.

- If realistic surface maps are your goal, then try and look at pictures ( or even better the real thing ) which show the kind of area you’re trying to reproduce. This should give you a good idea of the colours and the way they are “distributed” about the environment. Sometimes you may even be surprised at the colour combinations that actually occur in nature. Your local library, or even a local second hand book store, should have a number of landscape picture books which should provide ample inspiration. Keep in mind that older books might not have such good colour reproduction, older ones from the 60’s and 70’s featuring Britain seem to excel at lurid blues and oranges ! It can be interesting to see how both film and colour reproduction has improved over the years.

- It may help to think of creating a surface map as if you were painting the landscape. Block in large areas of colour with single sibling surface layers, and then go back and add children to those layers which have finer detail and colour variations. If you’re basing the surface map on real life or a photo, try squinting your eyes when looking at it to get an idea of the major colours in the scene.

- Try thinking of how a landscape is arranged in nature, and create surface layers accordingly. For example, rock is usually below dirt, and so you could create a rock layer near the top of the list, then create a dirt sibling layer. That way the dirt layer will cover the rock layer. Likewise, grass usually covers dirt, so you could then create a grass sibling layer, and that would always cover the dirt. In fact, because grass usually needs dirt to grow in, you could make the grass layer a child of the dirt layer, and the grass would only appear where dirt was able to appear on the landscape. That’s a somewhat simplistic view of it, but hopefully you see what I mean.

Version History

v1.0, 26/8/02 : Initial release.

surfacemapguide.pdf

Documents

Transcript of surfacemapguide.pdf