Add dynamic exposure correction (#12959)

* Add uniform for frame delta time
* Adjust exposure in logarithmic (EV) space
* Add network support and LUA API
* Add testing mod

games/devtest/mods/lighting/init.lua

@@ -0,0 +1,140 @@
+local lighting_sections = {
+	{n = "shadows", d = "Shadows",
+		entries = {
+			{ n = "intensity", d = "Shadow Intensity", min = 0, max = 1 }
+		}
+	},
+	{
+		n = "exposure", d = "Exposure",
+		entries = {
+			{n = "luminance_min", d = "Minimum Luminance", min = -10, max = 10},
+			{n = "luminance_max", d = "Maximum Luminance", min = -10, max = 10},
+			{n = "exposure_correction", d = "Exposure Correction", min = -10, max = 10},
+			{n = "speed_dark_bright", d = "Bright light adaptation speed", min = -10, max = 10, type="log2"},
+			{n = "speed_bright_dark", d = "Dark scene adaptation speed", min = -10, max = 10, type="log2"},
+			{n = "center_weight_power", d = "Power factor for center-weighting", min = 0.1, max = 10},
+		}
+	}
+}
+
+local function dump_lighting(lighting)
+	local result = "{\n"
+	local section_count = 0
+	for _,section in ipairs(lighting_sections) do
+		section_count = section_count + 1
+
+		local parameters = section.entries or {}
+		local state = lighting[section.n] or {}
+
+		result = result.."  "..section.n.." = {\n"
+
+		local count = 0
+		for _,v in ipairs(parameters) do
+			count = count + 1
+			result = result.."    "..v.n.." = "..(math.floor(state[v.n] * 1000)/1000)
+			if count < #parameters then
+				result = result..","
+			end
+			result = result.."\n"
+		end
+
+		result = result.."  }"
+
+		if section_count < #lighting_sections then
+			result = result..","
+		end
+		result = result.."\n"
+	end
+	result = result .."}"
+	return result
+end
+
+minetest.register_chatcommand("set_lighting", {
+	params = "",
+	description = "Tune lighting parameters",
+	func = function(player_name, param)
+		local player = minetest.get_player_by_name(player_name);
+		if not player then return end
+
+		local lighting = player:get_lighting()
+		local exposure = lighting.exposure or {}
+
+		local form = {
+			"formspec_version[2]",
+			"size[15,30]",
+			"position[0.99,0.15]",
+			"anchor[1,0]",
+			"padding[0.05,0.1]",
+			"no_prepend[]"
+		};
+
+		local line = 1
+		for _,section in ipairs(lighting_sections) do
+			local parameters = section.entries or {}
+			local state = lighting[section.n] or {}
+
+			table.insert(form, "label[1,"..line..";"..section.d.."]")
+			line  = line + 1
+
+			for _,v in ipairs(parameters) do
+				table.insert(form, "label[2,"..line..";"..v.d.."]")
+				table.insert(form, "scrollbaroptions[min=0;max=1000;smallstep=10;largestep=100;thumbsize=10]")
+				local value = state[v.n]
+				if v.type == "log2" then
+					value = math.log(value or 1) / math.log(2)
+				end
+				local sb_scale = math.floor(1000 * (math.max(v.min, value or 0) - v.min) / (v.max - v.min))
+				table.insert(form, "scrollbar[2,"..(line+0.7)..";12,1;horizontal;"..section.n.."."..v.n..";"..sb_scale.."]")
+				line = line + 2.7
+			end
+
+			line = line + 1
+		end
+
+		minetest.show_formspec(player_name, "lighting", table.concat(form))
+		local debug_value = dump_lighting(lighting)
+		local debug_ui = player:hud_add({type="text", position={x=0.1, y=0.3}, scale={x=1,y=1}, alignment = {x=1, y=1}, text=debug_value, number=0xFFFFFF})
+		player:get_meta():set_int("lighting_hud", debug_ui)
+	end
+})
+
+minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname ~= "lighting" then return end
+
+	if not player then return end
+
+	local hud_id = player:get_meta():get_int("lighting_hud")
+
+	if fields.quit then
+		player:hud_remove(hud_id)
+		player:get_meta():set_int("lighting_hud", -1)
+		return
+	end
+
+	local lighting = player:get_lighting()
+	for _,section in ipairs(lighting_sections) do
+		local parameters = section.entries or {}
+
+		local state = (lighting[section.n] or {})
+		lighting[section.n] = state
+
+		for _,v in ipairs(parameters) do
+			
+			if fields[section.n.."."..v.n] then
+				local event = minetest.explode_scrollbar_event(fields[section.n.."."..v.n])
+				if event.type == "CHG" then
+					local value = v.min + (v.max - v.min) * (event.value / 1000);
+					if v.type == "log2" then
+						value = math.pow(2, value);
+					end
+					state[v.n] = value;
+				end
+			end
+		end
+	end
+
+	local debug_value = dump_lighting(lighting)
+	player:hud_change(hud_id, "text", debug_value)
+
+	player:set_lighting(lighting)
+end)