Make options documentation consistent

also resolve confusion between Y axis on image vs. in-game

minetestmapper.6

@@ -9,9 +9,13 @@ minetestmapper \- generate an overview image of a Luanti map
 See additional optional parameters below.
 .SH DESCRIPTION
 .B minetestmapper
-generates an overview image of a Luanti map. This is a port of
-the original minetestmapper.py to C++, that is both faster and
-provides more functionality than the obsolete Python script.
+generates a top-down overview image of a Luanti map.
+This is a port of the obsolete minetestmapper.py script to C++,
+that is both faster and provides more features.
+
+Minetestmapper ships with a colors.txt file suitable for Minetest Game,
+if you use a different game or have mods installed you should generate a
+matching colors.txt for better results (colors will be missing otherwise).
 
 .SH MANDATORY PARAMETERS
 .TP
@@ -28,7 +32,7 @@ Background color of image, e.g. "--bgcolor #ffffff"
 
 .TP
 .BR \-\-scalecolor " " \fIcolor\fR
-Color of scale, e.g. "--scalecolor #000000"
+Color of scale marks and text, e.g. "--scalecolor #000000"
 
 .TP
 .BR \-\-playercolor " " \fIcolor\fR
@@ -40,11 +44,11 @@ Color of origin indicator, e.g. "--origincolor #ff0000"
 
 .TP
 .BR \-\-drawscale
-Draw tick marks
+Draw scale(s) with tick marks and numbers
 
 .TP
 .BR \-\-drawplayers
-Draw player indicators
+Draw player indicators with name
 
 .TP
 .BR \-\-draworigin
@@ -52,7 +56,7 @@ Draw origin indicator
 
 .TP
 .BR \-\-drawalpha
-Allow nodes to be drawn with transparency
+Allow nodes to be drawn with transparency (such as water)
 
 .TP
 .BR \-\-noshading
@@ -60,7 +64,7 @@ Don't draw shading on nodes
 
 .TP
 .BR \-\-noemptyimage
-Don't output anything when the image would be empty.
+Don't output anything when the image would be empty
 
 .TP
 .BR \-\-verbose
@@ -68,19 +72,21 @@ Enable verbose log output.
 
 .TP
 .BR \-\-min-y " " \fInumber\fR
-Don't draw nodes below this y value, e.g. "--min-y -25"
+Don't draw nodes below this Y value, e.g. "--min-y -25"
 
 .TP
 .BR \-\-max-y " " \fInumber\fR
-Don't draw nodes above this y value, e.g. "--max-y 75"
+Don't draw nodes above this Y value, e.g. "--max-y 75"
 
 .TP
 .BR \-\-backend " " \fIbackend\fR
-Use specific map backend; supported: \fIsqlite3\fP, \fIleveldb\fP, \fIredis\fP, \fIpostgresql\fP, e.g. "--backend leveldb"
+Override auto-detected map backend; supported: \fIsqlite3\fP, \fIleveldb\fP, \fIredis\fP, \fIpostgresql\fP, e.g. "--backend leveldb"
 
 .TP
 .BR \-\-geometry " " \fIgeometry\fR
-Limit area to specific geometry (\fIx:y+w+h\fP where x and y specify the lower left corner), e.g. "--geometry -800:-800+1600+1600"
+Limit area to specific geometry (\fIx:z+w+h\fP where x and z specify the lower left corner), e.g. "--geometry -800:-800+1600+1600"
+
+The coordinates are specified with the same axes as in-game. The Z axis becomes Y when projected on the image.
 
 .TP
 .BR \-\-extent
@@ -92,7 +98,7 @@ Zoom the image by using more than one pixel per node, e.g. "--zoom 4"
 
 .TP
 .BR \-\-colors " " \fIpath\fR
-Forcefully set path to colors.txt file (autodetected otherwise), e.g. "--colors ../world/mycolors.txt"
+Override auto-detected path to colors.txt, e.g. "--colors ../world/mycolors.txt"
 
 .TP
 .BR \-\-scales " " \fIedges\fR
@@ -102,12 +108,7 @@ Draw scales on specified image edges (letters \fIt b l r\fP meaning top, bottom,
 .BR \-\-exhaustive " " \fImode\fR
 Select if database should be traversed exhaustively or using range queries, available: \fInever\fP, \fIy\fP, \fIfull\fP, \fIauto\fP
 
-Defaults to \fIauto\fP. You shouldn't need to change this, but doing so can improve rendering times on large maps.
-For these optimizations to work it is important that you set
-.B min-y
-and
-.B max-y
-when you don't care about the world below e.g. -60 and above 1000 nodes.
+Defaults to \fIauto\fP. You shouldn't need to change this, as minetestmapper tries to automatically picks the best option.
 
 .TP
 .BR \-\-dumpblock " " \fIpos\fR