Making the feature map
A serious pain, but once it's done… Wow!
Open photoshop/gimp, make an image that is your texture map size / 8 which in my case is 1024×1024.
Grass, trees and geothermal vents
Time for technical details. To put grass on your feature map you use the blue colors, ranging from 0 to 255. The higher the amount, the more grass you have on that particular area. Simple enough.
Trees use the green color. To place a tree, use green colors from 200 - 215. I won't even bother posting pictures of the tree types, cause there are only 2. To place a tree, put a 1 pixel x 1 pixel dot on the feature map to place the tree. It comes in handy sometimes to open and resize your heightmap in photoshop, for the purpose of being able to see where your tree is being placed exactly.
At this point I might suggest users experiment with the 'Operations→Texture map→Generate alpha maps' option in L3DT (see official tutorial). This can export mask maps for the land types in your map, such as grass, so it might save you some painting effort. Admittedly, I've yet to try this approach when making a map for Spring, but it's what I've done when making the tree-maps for JohnJ's BattleTanks II game. Anyway, please try it out and let me know what you think. — aaron 2006/03/10 06:15
To place geovents, use 1×1 pixel of green 255. Make sure it is on a flat area and no trees or other features are near it.
Other features
Other features use descending order from red 255 to red 0. To put a feature on your map, you must have the object (in s30 or 3d0 format, I recommend s30 format because the collision detection is much better). You need the texture for the feature. For my map I used Smoth's palm trees.
This is where it gets extremely hard to explain. In your copy of mothers map converter (YOU DO HAVE IT DON'T YOU!?!? 
, if not, here is a link to my packaged version), one of the files you have should be fs.txt. This file is simply a listing of the features in your map. The first one listed corresponds to red 255. Here is my fs.txt for canyons:
pdrock1 pdrock1a pdrock2 pdrock2a pdrock3 pdrock3a pdrock4 pdrock4a pdrock4a palmetto_1 cluster0_dead cluster1 cluster1_dead cluster2 cluster2_dead palmetto_2 palmetto_3 cluster0
To place a feature on the feature map, use 1×1 pixel of red (color of your feature) on the feature map. It map also help you to know that a 1 x 1 pixel on the feature map roughly equals out to a 1×1 footprint in spring.
To add the features, you need to make a folder called “objects3d”, another folder called “features” with the sub directory “All Worlds”, and yet another called “unittextures”
Your directory structure should look like this:
c:\Mymapname features - All Worlds maps objects3d unittextures
Put the s30/3do in the objects3d folder. Put the tga/dds/png in the unittexture folder. Put the tdf file in the All Worlds folder.
A bit of side information here… The tdf is what defines the properties of the feature in question, for example, here is a copy of my tdf for palmetto_1:
[palmetto_1]
{
world=allworld;
description=Palmetto;
category=arm_corpses;
object=palmetto_1.s3o;
footprintx=2;
footprintz=2;
height=20;
blocking=0;
hitdensity=5;
energy=50;
damage=1000;
flammable=0;
reclaimable=1;
autoreclaimable=1;
featurereclamate=smudge01;
seqnamereclamate=tree1reclamate;
}
It may take a few tries to get things right, but don't give up. It will become clear to you quite quickly exactly how it works in game.
Save feature.bmp
For reference, here is what my feature map looks like:
You are now about 70(some odd) percent done.
Next section
Your guess is as good as mine. I guess we'll wait and see what Forboding Angel comes up with next, and what dopey suggestions Aaron can sprinkle about over it. Stay tuned.