From 97c4e91d3a3c1c378f678f28cca5c063d118e47b Mon Sep 17 00:00:00 2001
From: orwell96 <orwell@bleipb.de>
Date: Wed, 19 Dec 2018 22:29:07 +0100
Subject: Color lines according to depth, add bounds

---
 helpers.lua | 77 +++++++------------------------------------------------------
 main.lua    | 63 ++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 66 insertions(+), 74 deletions(-)

diff --git a/helpers.lua b/helpers.lua
index 511d32e..e9ea256 100644
--- a/helpers.lua
+++ b/helpers.lua
@@ -353,79 +353,18 @@ end
 local hext = { [0]="0",[1]="1",[2]="2",[3]="3",[4]="4",[5]="5",[6]="6",[7]="7",[8]="8",[9]="9",[10]="A",[11]="B",[12]="C",[13]="D",[14]="E",[15]="F"}
 local dect = { ["0"]=0,["1"]=1,["2"]=2,["3"]=3,["4"]=4,["5"]=5,["6"]=6,["7"]=7,["8"]=8,["9"]=9,["A"]=10,["B"]=11,["C"]=12,["D"]=13,["E"]=14,["F"]=15}
 
-local f = atfloor
-
-local function hex(i)
-	local x=i+32768
-	local c4 = x % 16
-	x = f(x / 16)
-	local c3 = x % 16
-	x = f(x / 16)
+
+-- Hex functions changed for 8bit
+function advtrains.hex(i)
+	local x=math.floor(i)
 	local c2 = x % 16
-	x = f(x / 16)
+	x = math.floor(x / 16)
 	local c1 = x % 16
-	return (hext[c1]) .. (hext[c2]) .. (hext[c3]) .. (hext[c4])
+	return (hext[c1]) .. (hext[c2])
 end
 
 local function c(s,i) return dect[string.sub(s,i,i)] end
 
-local function dec(s)
-	return (c(s,1)*4096 + c(s,2)*256 + c(s,3)*16 + c(s,4))-32768
-end
--- Takes a position vector and outputs a encoded value suitable as table index
--- This is essentially a hexadecimal representation of the position (+32768)
--- Order (YYY)YXXXXZZZZ
-function advtrains.encode_pos(pos)
-	return hex(pos.y) .. hex(pos.x) .. hex(pos.z)
-end
-
--- decodes a position encoded with encode_pos
-function advtrains.decode_pos(pts)
-	local stry = string.sub(pts, 1,4)
-	local strx = string.sub(pts, 5,8)
-	local strz = string.sub(pts, 9,12)
-	return vector.new(dec(strx), dec(stry), dec(strz))
-end
-
---[[ Benchmarking code
-local tdt = {}
-local tlt = {}
-local tet = {}
-
-for i=1,1000000 do
-	tdt[i] = vector.new(math.random(-65536, 65535), math.random(-65536, 65535), math.random(-65536, 65535))
-	if i%1000 == 0 then
-		tlt[#tlt+1] = tdt[i]
-	end
-end
-
-local t1=os.clock()
-for i=1,1000000 do
-	local pe = advtrains.encode_pos(tdt[i])
-	local pb = advtrains.decode_pos(pe)
-	tet[pe] = i
-end
-for i,v in ipairs(tlt) do
-	local lk = tet[advtrains.encode_pos(v)]
-end
-atdebug("endec",os.clock()-t1,"s")
-
-tet = {}
-
-t1=os.clock()
-for i=1,1000000 do
-	local pe = minetest.pos_to_string(tdt[i])
-	local pb = minetest.string_to_pos(pe)
-	tet[pe] = i
+function advtrains.dec(s)
+	return (c(s,1)*16 + c(s,2))
 end
-for i,v in ipairs(tlt) do
-	local lk = tet[minetest.pos_to_string(v)]
-end
-atdebug("pts",os.clock()-t1,"s")
-
---Results:
---2018-11-29 16:57:08: ACTION[Main]: [advtrains]endec 1.786451 s 
---2018-11-29 16:57:10: ACTION[Main]: [advtrains]pts 2.566377 s 
-]]
-
-
diff --git a/main.lua b/main.lua
index 6b7323d..a99fe7c 100644
--- a/main.lua
+++ b/main.lua
@@ -5,13 +5,24 @@
 local maxc = 5000
 
 -- embed an image called "world.png"
-local wimg = true
+local wimg = false
 -- image file resolution (not world resolution!)
 local wimresx = 3000
 local wimresy = 3000
 -- one pixel is ... nodes
 local wimscale = 4
 
+-- y ranges and line colors
+-- Minimum y level drawn
+local drminy = -30
+-- Color of min y level
+local colminy = {r=0, g=0, b=255}
+-- Maximum y level drawn
+local drmaxy = 70
+-- Color of max y level
+local colmaxy = {r=255, g=0, b=0}
+
+
 datapath = (arg[1] or "").."/"
 
 
@@ -111,7 +122,7 @@ svgfile:write('viewBox="'..(-maxc)..' '..(-maxc)..' '..(2*maxc)..' '..(2*maxc)..
 
 
 svgfile:write([[
-<circle cx="0" cy="0" r="2" stroke="red" stroke-width="1" />
+<circle cx="0" cy="0" r="5" stroke="red" stroke-width="1" />
 ]])
 
 if wimg then
@@ -183,16 +194,58 @@ end
 
 plcnt = 0
 
+
+local function hexcolor(clr)
+	return "#"..advtrains.hex(clr.r)..advtrains.hex(clr.g)..advtrains.hex(clr.b)
+end
+
+local function cfactor(ry)
+	local y = ry - (ry%4)
+
+	local fac = (y-drminy)/(drmaxy-drminy)
+	return fac
+end
+
+local function pl_header(fac)
+	
+	local color = {
+		r = colminy.r + (colmaxy.r-colminy.r)*fac,
+		g = colminy.g + (colmaxy.g-colminy.g)*fac,
+		b = colminy.b + (colmaxy.b-colminy.b)*fac,
+	}
+	
+	local c = hexcolor(color)
+	return '<polyline style="fill:none;stroke:'..c..';stroke-width:1" points="'
+end
+
 local function polyline_write(pl)
-	local str = {'<polyline style="fill:none;stroke:black;stroke-width:1" points="'}
+	local p1y = cfactor(pl[1].y)
+	local str = {pl_header(p1y)}
 	
 	local i
 	local e
+	local lastcf = p1y
 	local lastldir = {x=0, y=0}
 	for i=1,#pl do
 		e = pl[i]
-		-- Note that we mirror y, so positive z is up
-		table.insert(str, e.x .. "," .. -(e.z) .. " ")
+		local cf = cfactor(e.y)
+		if cf ~= lastcf then
+			if lastcf <= 1 and lastcf >= 0 then
+				-- insert final point
+				-- Note that we mirror y, so positive z is up
+				table.insert(str, e.x .. "," .. -(e.z) .. " ")
+				table.insert(str, '" />\n')
+				plcnt = plcnt + 1
+			end
+			if cf <= 1 and cf >= 0 then
+				table.insert(str, pl_header(cf))
+			end
+		end
+		if cf <= 1 and cf >= 0 then
+			-- Note that we mirror y, so positive z is up
+			table.insert(str, e.x .. "," .. -(e.z) .. " ")
+		end
+		lastcf = cf
 	end
 	
 	table.insert(str, '" />\n')
-- 
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