forked from minetest-mods/nether
Add Surface-following portal using Moore curves
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Treer
SmallJoker
parent
11a818212a
commit
b9e85582f9
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@ -96,11 +96,17 @@ Requiring 14 blocks of ice, but otherwise constructed the same as the portal to
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end,
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})
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nether.register_portal("stargate_portal", {
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-- These Moore Curve functions requred by circular_portal's find_surface_anchorPos() will
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-- be assigned later in this file.
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local get_moore_distance -- will be function get_moore_distance(cell_count, x, y): integer
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local get_moore_coords -- will be function get_moore_coords(cell_count, distance): pos2d
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nether.register_portal("circular_portal", {
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shape = nether.PortalShape_Circular,
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frame_node_name = "default:stone",
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frame_node_name = "default:cobble",
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wormhole_node_color = 4, -- 4 is cyan
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book_of_portals_pagetext = S([[ ──══♦♦♦◊ Shape testing portal ◊♦♦♦══──
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book_of_portals_pagetext = S([[ ──══♦♦♦◊ Surface portal ◊♦♦♦══──
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┌═╤═╤═╗
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┌═┼─┴─┴─┼═╗
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@ -114,46 +120,188 @@ nether.register_portal("stargate_portal", {
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]] .. "\u{25A9}"),
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is_within_realm = function(pos) -- return true if pos is inside the Nether
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return pos.y < nether.DEPTH
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is_within_realm = function(pos)
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-- Always return true, because these portals always just take you around the surface
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-- rather than taking you to a realm
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return true
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end,
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find_realm_anchorPos = function(surface_anchorPos)
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-- divide x and z by a factor of 8 to implement Nether fast-travel
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local destination_pos = vector.divide(surface_anchorPos, nether.FASTTRAVEL_FACTOR)
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destination_pos.x = math.floor(0.5 + destination_pos.x) -- round to int
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destination_pos.z = math.floor(0.5 + destination_pos.z) -- round to int
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destination_pos.y = nether.DEPTH - 1000 -- temp value so find_nearest_working_portal() returns nether portals
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-- a y_factor of 0 makes the search ignore the altitude of the portals (as long as they are in the Nether)
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local existing_portal_location, existing_portal_orientation = nether.find_nearest_working_portal("stargate_portal", destination_pos, 8, 0)
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if existing_portal_location ~= nil then
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return existing_portal_location, existing_portal_orientation
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else
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local start_y = nether.DEPTH - math.random(500, 1500) -- Search starting altitude
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destination_pos.y = nether.find_nether_ground_y(destination_pos.x, destination_pos.z, start_y)
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return destination_pos
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end
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-- This function isn't needed, since this type of portal always goes to the surface
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minecraft.log("error" , "find_realm_anchorPos called for surface portal")
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return {x=0, y=0, z=0}
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end,
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find_surface_anchorPos = function(realm_anchorPos)
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-- A portal definition doesn't normally need to provide a find_surface_anchorPos() function,
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-- since find_surface_target_y() will be used by default, but Nether portals also scale position
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-- to create fast-travel. Defining a custom function also means we can look for existing nearby portals:
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-- since find_surface_target_y() will be used by default, but these portals travel around the
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-- surface (following a Moore curve) so will be using a different x and z to realm_anchorPos.
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-- Multiply x and z by a factor of 8 to implement Nether fast-travel
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local destination_pos = vector.multiply(realm_anchorPos, nether.FASTTRAVEL_FACTOR)
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destination_pos.x = math.min(30900, math.max(-30900, destination_pos.x)) -- clip to world boundary
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destination_pos.z = math.min(30900, math.max(-30900, destination_pos.z)) -- clip to world boundary
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destination_pos.y = 0 -- temp value so find_nearest_working_portal() doesn't return nether portals
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local cellCount = 512
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local travelDistanceInCells = 10
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local maxDistFromOrigin = 30000 -- the world edges are at X=30927, X=−30912, Z=30927 and Z=−30912
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-- a y_factor of 0 makes the search ignore the altitude of the portals (as long as they are outside the Nether)
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local existing_portal_location, existing_portal_orientation = nether.find_nearest_working_portal("stargate_portal", destination_pos, 8 * nether.FASTTRAVEL_FACTOR, 0)
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-- clip realm_anchorPos to maxDistFromOrigin, and move the origin so that all values are positive
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local x = math.min(maxDistFromOrigin, math.max(-maxDistFromOrigin, realm_anchorPos.x)) + maxDistFromOrigin
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local z = math.min(maxDistFromOrigin, math.max(-maxDistFromOrigin, realm_anchorPos.z)) + maxDistFromOrigin
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local divisor = math.ceil(maxDistFromOrigin * 2 / cellCount)
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local distance = get_moore_distance(cellCount, math.floor(x / divisor + 0.5), math.floor(z / divisor + 0.5))
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local destination_distance = (distance + travelDistanceInCells) % (cellCount * cellCount)
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local moore_pos = get_moore_coords(cellCount, destination_distance)
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-- deterministically look for a location where get_spawn_level() gives us a height
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local target_x = moore_pos.x * divisor - maxDistFromOrigin
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local target_z = moore_pos.y * divisor - maxDistFromOrigin
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local prng = PcgRandom( -- seed the prng so that all portals for these Moore Curve coords will use the same random location
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moore_pos.x * 65732 +
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moore_pos.y * 729 +
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minetest.get_mapgen_setting("seed") * 3
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)
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local radius = divisor / 2 - 2
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local attemptLimit = 10
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local adj_x, adj_z
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for attempt = 1, attemptLimit do
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adj_x = math.floor(prng:rand_normal_dist(-radius, radius, 2) + 0.5)
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adj_z = math.floor(prng:rand_normal_dist(-radius, radius, 2) + 0.5)
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minetest.chat_send_all(attempt .. ": x " .. target_x + adj_x .. ", z " .. target_z + adj_z)
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if minetest.get_spawn_level(target_x + adj_x, target_z + adj_z) ~= nil then
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-- found a location which will be at ground level (unless a player has built there)
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minetest.chat_send_all("x " .. target_x + adj_x .. ", z " .. target_z + adj_z .. " is suitable")
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break
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end
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end
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local destination_pos = {x = target_x + adj_x, y = 0, z = target_z + adj_z}
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-- a y_factor of 0 makes the search ignore the altitude of the portals
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local existing_portal_location, existing_portal_orientation = nether.find_nearest_working_portal("circular_portal", destination_pos, radius, 0)
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if existing_portal_location ~= nil then
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return existing_portal_location, existing_portal_orientation
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else
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destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "stargate_portal")
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destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "circular_portal")
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return destination_pos
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end
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end
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})
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--=========================================--
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-- Hilbert curve and Moore curve functions --
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--=========================================--
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-- These are space-filling curves, used by the circular_portal example as a way to determine where
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-- to place portals. https://en.wikipedia.org/wiki/Moore_curve
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-- Flip a quadrant on its diagonal axis
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-- cell_count is the number of cells across the square is split into, and must be a power of 2
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-- if flip_twice is true then pos does not change (any even numbers of flips would cancel out)
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-- if flip_direction is true then the position is flipped along the \ diagonal
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-- if flip_direction is false then the position is flipped along the / diagonal
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local function hilbert_flip(cell_count, pos, flip_direction, flip_twice)
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if not flip_twice then
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if flip_direction then
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pos.x = (cell_count - 1) - pos.x;
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pos.y = (cell_count - 1) - pos.y;
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end
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local temp_x = pos.x;
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pos.x = pos.y;
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pos.y = temp_x;
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end
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end
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local function test_bit(cell_count, value, flag)
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local bit_value = cell_count / 2
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while bit_value > flag and bit_value >= 1 do
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if value >= bit_value then value = value - bit_value end
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bit_value = bit_value / 2
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end
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return value >= bit_value
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end
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-- Converts (x,y) to distance
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-- starts at bottom left corner, i.e. (0, 0)
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-- ends at bottom right corner, i.e. (cell_count - 1, 0)
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local function get_hilbert_distance (cell_count, x, y)
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local distance = 0
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local pos = {x=x, y=y}
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local rx, ry
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local s = cell_count / 2
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while s > 0 do
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if test_bit(cell_count, pos.x, s) then rx = 1 else rx = 0 end
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if test_bit(cell_count, pos.y, s) then ry = 1 else ry = 0 end
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local rx_XOR_ry = rx
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if ry == 1 then rx_XOR_ry = 1 - rx_XOR_ry end -- XOR'd ry against rx
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distance = distance + s * s * (2 * rx + rx_XOR_ry)
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hilbert_flip(cell_count, pos, rx > 0, ry > 0);
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s = math.floor(s / 2)
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end
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return distance;
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end
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-- Converts distance to (x,y)
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local function get_hilbert_coords(cell_count, distance)
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local pos = {x=0, y=0}
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local rx, ry
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local s = 1
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while s < cell_count do
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rx = math.floor(distance / 2) % 2
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ry = distance % 2
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if rx == 1 then ry = 1 - ry end -- XOR ry with rx
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hilbert_flip(s, pos, rx > 0, ry > 0);
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pos.x = pos.x + s * rx
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pos.y = pos.y + s * ry
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distance = math.floor(distance / 4)
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s = s * 2
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end
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return pos
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end
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-- Converts (x,y) to distance
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-- A Moore curve is a variation of the Hilbert curve that has the start and
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-- end next to each other.
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-- Top middle point is the start/end location
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get_moore_distance = function(cell_count, x, y)
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local quadLength = cell_count / 2
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local quadrant = 1 - math.floor(y / quadLength)
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if math.floor(x / quadLength) == 1 then quadrant = 3 - quadrant end
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local flipDirection = x < quadLength
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local pos = {x = x % quadLength, y = y % quadLength}
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hilbert_flip(quadLength, pos, flipDirection, false)
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return (quadrant * quadLength * quadLength) + get_hilbert_distance(quadLength, pos.x, pos.y)
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end
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-- Converts distance to (x,y)
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-- A Moore curve is a variation of the Hilbert curve that has the start and
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-- end next to each other.
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-- Top middle point is the start/end location
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get_moore_coords = function(cell_count, distance)
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local quadLength = cell_count / 2
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local quadDistance = quadLength * quadLength
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local quadrant = math.floor(distance / quadDistance)
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local flipDirection = distance * 2 < cell_count * cell_count
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local pos = get_hilbert_coords(quadLength, distance % quadDistance)
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hilbert_flip(quadLength, pos, flipDirection, false)
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if quadrant >= 2 then pos.x = pos.x + quadLength end
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if quadrant % 3 == 0 then pos.y = pos.y + quadLength end
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return pos
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end
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