The size of the maps are limited to about 36 Square kilometres. That is, any combination that does not exceed this number (6 x 6; 8 x 4; etc.). For MP maps we try to find out the best size. But we recommend they not be larger than 2 x 3 km.
I will explain the generation of the maps with Photoshop. It worked fine for me and I have the experience to handle the software. Other programs should do as well and everybody has to make this decision on his own.
Scanning of the map
We assume we have a 1:25,000 map. Four centimetres represents 1 kilometre. Then a scan with 300 dpi or 600 dpi is the best choice. This is how to calculate it: 300 pixels = 2.54 cm (1 inch). Therefore, if x pixels = 4 cm (meaning 1 kilometre on the map at a scale of 1:25,000), then x = 4 x 300 / 2.54 = 472 pixels = 1 km.
The 300 dpi scan
On a 300 dpi scan, 1 km = 472 pixels. Therefore 2 kms = 944 pixels, etc. I say kilomteres and not miles because the maps are mostly in the metric system.
The 600 dpi scan
On a 600 dpi scan, 1 km = 944 pixels. 2 kms = 1888 pixels, etc.
Select the area
In Photoshop you open the scan. Then you have to select the desired area of the map. (Remember the limitations!)
Use the marquee tool with the option 'fixed size'. In the boxes for the fixed size you fill in the number of pixels (Example: you want a map 4 km high and 6 km wide, that is 1888 x 2832 pixels for the 1:25,000 scan).
Then use the 'crop function' to cut out the desired area. You now have a section map representing 4 km x 6 km.
Next step is to resize you map and save it as a grayscale .BMP file.
Open the 'Image size' window. In the boxes that show the width and the height of the image in pixels, fill in the following:
Assume your map should be 5 x 7 kms; then enter 500 x 700 pixels. This is necessary to match the ingame scale of PE (which is 10 m / Heightmap pixel).
Save yourmap as XXXscan.bmp in grayscale mode. (XXX meaning the name of the area/town on the map).
Then add a new layer. This layer will be the layer you draw the heightlines on.
Drawing the heightlines
We are now in grayscale-mode. This means that we only got 256 different grey colors. This means we can cover 256 metres of height in one map. If you have more, then fake it and nobody will see if the hill out there is really 300 metres high or only 256 metres.
Select the heightline with the lowest value on the map. Remember: the values from 0 to 256 are not fixed numbers and they have only a relative value. This means: when the lowest line on the map reads 40 metres then you can assign the value of 0 or 10 (or....) to this height. The only thing you have to do now is adjusting the other grayscale values acordingly to the other heightlines.
40 metres on the map = RBB value of 10 for the heightline
60 metres on the map = RGB value of 30 for the heightline
Creating the roughness map
The other part for generating a map is the so-called roughness map. This map determines how rough the area can be on various parts of the landscape. To admit: this part never worked quite well. Let me explain why: You can assign values from 0 to 256 for the roughness. 0 is extremely smooth, 256 extremely rough. Our experiences showed us that even when you paint the whole area in 0 the map is still rough enough.
Our tip: create a new layer over the heightlines. Open the color-box of PS and cchoose the RGB value of 0,0,0.
Assign this color with the paintbucket to the whole map. Throw away the heightline layer and save the now totally black image as XXXr.bmp in greyscale-mode. (r stands for Roughness)
Generating the final map
Now you have 3 files in the same size: the scan, the heightlines and the roughness.
The scan we need later when assigning objects to the map in the scenario editor.
The other two files we need right now.
We wrote a simple DOS-program that links the two files together, thus creating a height profile.
Be sure both files you want to link are in the same folder as the map generating program. The map generating program consists of 2 files. The program's start batch is mkmap.exe. The other file the program needs is the dos4gw.exe. You have to open a DOS-box and then change to the appropriate folder.
The syntax to start the program is: mkmap High.bmp rough.bmp finish.bmp
Example: mkmap xxxh.bmp xxxr.bmp xxxheight.bmp
It is important to follow the nomenclature rules. The PE engine needs two files. One is the scan' file you created first and it has to be named xxxscan.bmp. The other you are now creating has to be named xxxheight.bmp!!!!
The original heightness and roughness files are not needed anymore (except for corrections). The xxxheight.bmp file and the xxxscan.bmp file have to be delivered to someone who has access to the Scenario Editor. He will assign textures and objects to the landscape and make it ready for play.