Improved the fade transitions between [time_area]s

The n,ne,se,s,sw,nw-style transitions don't work well with transparency, so this makes the transitions corner-based which allows the fade to be longer and smoother.

src/display.cpp

@@ -1110,20 +1110,90 @@ std::vector<surface> display::get_terrain_images(const map_location &loc,
 	//get all the light transitions
 	map_location adjs[6];
 	get_adjacent_tiles(loc,adjs);
+
 	for(int d=0; d<6; ++d){
-		const time_of_day& atod = get_time_of_day(adjs[d]);
-		if(atod.color == tod.color)
+		/* concave
+		  _____
+		 /     \
+		/ atod1 \_____
+		\ !tod  /     \
+		 \_____/ atod2 \
+		 /  \__\ !tod  /
+		/       \_____/
+		\  tod  /
+		 \_____/*/
+
+		const time_of_day& atod1 = get_time_of_day(adjs[d]);
+		const time_of_day& atod2 = get_time_of_day(adjs[(d + 1) % 6]);
+
+		if(atod1.color == tod.color || atod2.color == tod.color || atod1.color != atod2.color)
 			continue;
 
 		if(lt.empty()) {
 			//color the full hex before adding transitions
 			tod_color col = tod.color + color_adjust_;
-			lt = image::get_light_string(6, col.r, col.g, col.b);
+			lt = image::get_light_string(0, col.r, col.g, col.b);
 		}
 
 		// add the directional transitions
-		tod_color acol = atod.color + color_adjust_;
-		lt += image::get_light_string(d, acol.r, acol.g, acol.b);
+		tod_color acol = atod1.color + color_adjust_;
+		lt += image::get_light_string(d + 1, acol.r, acol.g, acol.b);
+	}
+	for(int d=0; d<6; ++d){
+		/* convex 1
+		  _____
+		 /     \
+		/ atod1 \_____
+		\ !tod  /     \
+		 \_____/ atod2 \
+		 /  \__\  tod  /
+		/       \_____/
+		\  tod  /
+		 \_____/*/
+
+		const time_of_day& atod1 = get_time_of_day(adjs[d]);
+		const time_of_day& atod2 = get_time_of_day(adjs[(d + 1) % 6]);
+
+		if(atod1.color == tod.color || atod1.color == atod2.color)
+			continue;
+
+		if(lt.empty()) {
+			//color the full hex before adding transitions
+			tod_color col = tod.color + color_adjust_;
+			lt = image::get_light_string(0, col.r, col.g, col.b);
+		}
+
+		// add the directional transitions
+		tod_color acol = atod1.color + color_adjust_;
+		lt += image::get_light_string(d + 7, acol.r, acol.g, acol.b);
+	}
+	for(int d=0; d<6; ++d){
+		/* convex 2
+		  _____
+		 /     \
+		/ atod1 \_____
+		\  tod  /     \
+		 \_____/ atod2 \
+		 /  \__\ !tod  /
+		/       \_____/
+		\  tod  /
+		 \_____/*/
+
+		const time_of_day& atod1 = get_time_of_day(adjs[d]);
+		const time_of_day& atod2 = get_time_of_day(adjs[(d + 1) % 6]);
+
+		if(atod2.color == tod.color || atod1.color == atod2.color)
+			continue;
+
+		if(lt.empty()) {
+			//color the full hex before adding transitions
+			tod_color col = tod.color + color_adjust_;
+			lt = image::get_light_string(0, col.r, col.g, col.b);
+		}
+
+		// add the directional transitions
+		tod_color acol = atod2.color + color_adjust_;
+		lt += image::get_light_string(d + 13, acol.r, acol.g, acol.b);
 	}
 
 	if(lt.empty()){

src/image.cpp

@@ -593,12 +593,16 @@ static surface apply_light(surface surf, const light_string& ls){
 	if(i != lightmaps_.end()) {
 		lightmap = i->second;
 	} else {
-		//build all the 7 paths for lightmap sources
-		static const std::string p = "terrain/light";
-		static const std::string lm_img[7] = {
-			p+"-n.png", p+"-ne.png", p+"-se.png",
-			p+"-s.png", p+"-sw.png", p+"-nw.png",
-			p+".png"
+		//build all the paths for lightmap sources
+		static const std::string p = "terrain/light/light";
+		static const std::string lm_img[19] = {
+			p+".png",
+			p+"-concave-2-tr.png", p+"-concave-2-r.png", p+"-concave-2-br.png",
+			p+"-concave-2-bl.png", p+"-concave-2-l.png", p+"-concave-2-tl.png",
+			p+"-convex-br-bl.png", p+"-convex-bl-l.png", p+"-convex-l-tl.png",
+			p+"-convex-tl-tr.png", p+"-convex-tr-r.png", p+"-convex-r-br.png",
+			p+"-convex-l-bl.png", p+"-convex-tl-l.png", p+"-convex-tr-tl.png",
+			p+"-convex-r-tr.png", p+"-convex-br-r.png", p+"-convex-bl-br.png"
 		};
 
 		//decompose into atomic lightmap operations (4 chars)

src/image.hpp

@@ -136,7 +136,11 @@ namespace image {
 	///light_string store colors info of central and adjacent hexes.
 	///The structure is one or several 4 chars blocks (L,R,G,B)
 	///where RGB is the color and L is the lightmap to use:
-	///(-1:none, 0-5:transition in each direction, 6:full hex)
+    ///   -1: none
+    ///    0: full hex
+    ///  1-6: concave corners
+    /// 7-12: convex half-corners 1
+    ///13-19: convex half-corners 2
 	typedef std::basic_string<signed char> light_string;
 	///return light_string of one light operation(see above)
 	light_string get_light_string(int op, int r, int g, int b);