Post your modding questions here

[Nathan.S]

How do I go about finding a node to the left or right of the placed node, I can find nodes behind, in front, above and below, but I need to figure out a node to the side so I can modify either the node next in line or the node being placed.

[prestidigitator]

How do I go about finding a node to the left or right of the placed node, I can find nodes behind, in front, above and below, but I need to figure out a node to the side so I can modify either the node next in line or the node being placed.

It sort of depends on what you mean by, "left/right." Probably a vector cross product (not included in Minetest's 'vector.*' API) will be helpful:

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local function vectorCross(v1, v2)
   return { x = v1.y * v2.z - v1.z * v2.y,
            y = v1.z * v2.x - v1.x * v2.z,
            z = v1.x * v2.y - v1.y * v2.x };
end;


Then you'd want to cross the "forward" direction with the "up" direction. If "forward" and "up" aren't perpendicular (for example if "forward" is the direction the player is looking), you'd want to normalize the result:

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local upDir = { x = 0, y = 0, z = 1 };  -- EDIT: oops! no, should be {x=0,y=1,z=0}
local rightDir = vector.normalize(vectorCross(forwardDir, upDir));  -- EDIT: oops! no, should reverse forward/up


(Things would be more complicated if you were allowed to tip your head to the side like touching your ear to your shoulder, but by design this never happens in Minetest.) Now you have a vector pointing straight to the camera's right. To find a node "in that direction" you PROBABLY want to figure out which of the x or y coordinates has the biggest magnitude (unless you want to consider diagonals...?):

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local function cardinalDirection(vec)
   local x, y = vec.x, vec.y;
   local xm, ym = math.abs(x), math.abs(y);
   if xm >= ym then
      return { x = x / xm, y = 0, z = 0 };
   else
      return { x = 0, y = y / ym, z = 0 };
   end;
end;


[Nathan.S]

Thank you for the response, I'll have to try this out. I have a wall mod I'm working on with DonBatman, and we need a function like this.

[Don]

How do I go about finding a node to the left or right of the placed node, I can find nodes behind, in front, above and below, but I need to figure out a node to the side so I can modify either the node next in line or the node being placed.

It sort of depends on what you mean by, "left/right." Probably a vector cross product (not included in Minetest's 'vector.*' API) will be helpful:

Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.

Code: Select all

local function vectorCross(v1, v2)
   return { x = v1.y * v2.z - v1.z * v2.y,
            y = v1.z * v2.x - v1.x * v2.z,
            z = v1.x * v2.y - v1.y * v2.x };
end;


Then you'd want to cross the "forward" direction with the "up" direction. If "forward" and "up" aren't perpendicular (for example if "forward" is the direction the player is looking), you'd want to normalize the result:

Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.

Code: Select all

local upDir = { x = 0, y = 0, z = 1 };
local rightDir = vector.normalize(vectorCross(forwardDir, upDir));


(Things would be more complicated if you were allowed to tip your head to the side like touching your ear to your shoulder, but by design this never happens in Minetest.) Now you have a vector pointing straight to the camera's right. To find a node "in that direction" you PROBABLY want to figure out which of the x or y coordinates has the biggest magnitude (unless you want to consider diagonals...?):

Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.

Code: Select all

local function cardinalDirection(vec)
   local x, y = vec.x, vec.y;
   local xm, ym = math.abs(x), math.abs(y);
   if xm >= ym then
      return { x = x / xm, y = 0, z = 0 };
   else
      return { x = 0, y = y / ym, z = 0 };
   end;
end;


Any chance you could give a link to the lua? I don't understand what you are doing here. I would love to learn it

[prestidigitator]

Any chance you could give a link to the lua? I don't understand what you are doing here. I would love to learn it

I wrote the Lua for the response. I'd be happy to help with bits that are unclear though, if you elaborate on what is unclear.

[Hybrid Dog]

prestigator: Does this use the cross product in some way too?
viewtopic.php?p=174387#p174387

btw: l just managed to spawn a triangle surface:


its not as thin as possible, see the light at the 1/math.huge small edges


and l think this may help understanding this random looking appearance l showed at viewtopic.php?p=176501#p176501 and viewtopic.php?p=176569#p176569


its not real random

[prestidigitator]

prestigator: Does this use the cross product in some way too?
viewtopic.php?p=174387#p174387

Yes, it does, and I forgot two critical things, actually:

• Minetest's up is y, not z, so upDir should have been {x=0, y=1, z=0}.
• Minetest uses a fricking left-handed coordinate system for some stupid reason (probably because that's the OpenGL default and you need to set transformations if you want to fix it), so my cross product function should have reversed the up/forward directions.

This test:

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math.abs(dir.x) < math.abs(dir.z)

is being used to test which if the x or z directions the viewer is NOT looking in (equivalent to finding the cardinal direction they ARE looking in and finding the orthogonal/cross-product). Then the statements:

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right_pos.x = right_pos.x+dir.z/math.abs(dir.z)
-- or
right_pos.z = right_pos.z-dir.x/math.abs(dir.x)

basically carry an implicit cross product, determination of cardinal direction, and vector sum. Using the functions I posted above (if fixed), this would be equivalent to:

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Code: Select all

local forwardDir = placer:get_look_dir();
local upDir = { x = 0, y = 1, z = 0 };  -- fixed
local rightDir = vector.normalize(vectorCross(upDir, forwardDir));  -- fixed
local rightInc = cardinalDirection(rightDir);
local rightPos = vector.add(pos, rightInc);

The code you linked to does this in basically a single step, so it is more efficient, though (IMO) a little harder to follow. Actually, since the cross product is just being used to determine cardinal direction, you can leave out the (expensive) normalization step too, leaving just:

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Code: Select all

local forwardDir = placer:get_look_dir();
local upDir = { x = 0, y = 1, z = 0 };  -- fixed
local rightVec = vectorCross(upDir, forwardDir);  -- fixed
local rightInc = cardinalDirection(rightVec);
local rightPos = vector.add(pos, rightInc);

[prestidigitator]

Oh, here's another interesting tidbit. If the player is looking (exactly!) straight up or down, both pieces of logic might fail. In that case Player:get_look_yaw() MIGHT be able to resolve the problem, but I haven't tried it (depends on whether it depends on the look direction like our code here, or whether it uses additional knowledge such as the client has about the direction the player is facing prior to tilting the head up/down).

EDIT: For example, if yaw works in all cases and you want an unambiguous "right" direction relative to the camera, use:

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local function rightDir()
   local ang = (player:get_look_yaw() - 0.25*math.pi) % (2*math.pi);
   if ang < 0.5*math.pi then
      return { x = 1, y = 0, z = 0 };
   elseif ang < math.pi then
      return { x = 0, y = 0, z = 1 };
   elseif ang < 1.5*math.pi then
      return { x = -1, y = 0, z = 0 };
   else
      return { x = 0, y = 0, z = -1 };
   end;
end;

local rightPos = vector.add(pos, rightDir());


Note that unlike the coordinate axes, the yaw angle IS right-handed (increases counter-clockwise, starting to the east/+x).

[rubenwardy]

Why is using a left handed coordinate system stupid?

[Hybrid Dog]

as far as l know its impossible to look exactly straight up or down

[prestidigitator]

Why is using a left handed coordinate system stupid?

Because it's the world-wide convention in math and physics to use a right-handed coordinate system. Neglecting that bias it is fine, of course. :-p

[prestidigitator]

as far as l know its impossible to look exactly straight up or down

Interesting. Okay. Yeah, that seems to be true. As far as I can tell the client does seem to be limiting the camera pitch so that the y coordinate's magnitude is around 0.99992.

[Don]

Any chance you could give a link to the lua? I don't understand what you are doing here. I would love to learn it

I wrote the Lua for the response. I'd be happy to help with bits that are unclear though, if you elaborate on what is unclear.

Thanks for the offer. I found what I was looking for. I think I have a better understanding now. Hybrid Dog helped me a lot not too long ago. I appreciate how helpful everyone is.

[Rui]

[DELETED]

[TenPlus1]

Rui, the above code would have to check a lot of water causing lag issues, try this snippet from Ethereal mod instead:

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-- If torch or plants touching water then drop as item
minetest.register_abm({
   nodenames = {"default:torch", "group:flora"},
   neighbors = {"group:water"},
   interval = 5,
   chance = 1,
   action = function(pos, node)
      local num = #minetest.find_nodes_in_area({x=pos.x-1, y=pos.y, z=pos.z}, {x=pos.x+1, y=pos.y, z=pos.z}, {"group:water"})
      num = num + #minetest.find_nodes_in_area({x=pos.x, y=pos.y, z=pos.z-1}, {x=pos.x, y=pos.y, z=pos.z+1}, {"group:water"})
      num = num + #minetest.find_nodes_in_area({x=pos.x, y=pos.y+1, z=pos.z}, {x=pos.x, y=pos.y+1, z=pos.z}, {"group:water"})
      if num > 0 then
         minetest.set_node(pos, {name="default:water_flowing"})
         minetest.add_item(pos, {name = node.name})
      end
   end,
})

[Rui]

[DELETED]

[BrunoMine]

How can I check if a player in coordinated (100, 100, 100)?

[rubenwardy]

How can I check if a player in coordinated (100, 100, 100)?

Pretty trivial.

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local position = player:getpos()

if math.floor(position.x) == 100 and math.floor(position.y) == 100 and math.floor(position.z) == 100 then

end


If you don't have a player, you can get one by name:

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local player = minetest.get_player_by_name("player12")


[BrunoMine]

Is there a simpler way? I want to prevent a player can put a block in on a coordinate that there is already a player.
note: players use this technique to view caves through the wall (x scann).

[Hybrid Dog]

Is there a simpler way? I want to prevent a player can put a block in on a coordinate that there is already a player.
note: players use this technique to view caves through the wall (x scann).

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Code: Select all

local protected = minetest.is_protected
function minetest.is_protected(pos, ...)
   local v = protected(pos, ...)
   if v then
      return v
   end
   for _,player in pairs(minetest.get_connected_players()) do
      local ppos = vector.round(player:getpos())
      local in_node = vector.equals(ppos, pos)
      if not in_node then
         ppos.y = ppos.y+1
         in_node = vector.equals(ppos, pos)
      end
      if in_node then
         return true
      end
   end
   return v
end


[BrunoMine]

Is there a simpler way? I want to prevent a player can put a block in on a coordinate that there is already a player.
note: players use this technique to view caves through the wall (x scann).

Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.

Code: Select all

local protected = minetest.is_protected
function minetest.is_protected(pos, ...)
   local v = protected(pos, ...)
   if v then
      return v
   end
   for _,player in pairs(minetest.get_connected_players()) do
      local ppos = vector.round(player:getpos())
      local in_node = vector.equals(ppos, pos)
      if not in_node then
         ppos.y = ppos.y+1
         in_node = vector.equals(ppos, pos)
      end
      if in_node then
         return true
      end
   end
   return v
end


I improved a little bit.
Order to save server memory. (The focus of this check is mining)

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Code: Select all

local protected = minetest.is_protected
function minetest.is_protected(pos)
   local v = protected(pos)
   if v then
      return v
   end
   if pos.y > 80 then
      return v
   end
   for _,player in pairs(minetest.get_connected_players()) do
      local ppos = vector.round(player:getpos())
      local in_node = vector.equals(ppos, pos)
      if not in_node then
         ppos.y = ppos.y+1
         in_node = vector.equals(ppos, pos)
      end
      if in_node then
         return true
      end
   end
   return v
end


Thank you.
This was a big step for safety in minemacro server.

[CWz]

Hello again i am trying to set up tnt so it will require a priv but it seems to crash

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minetest.register_node("tnt:tnt", {
   description = "TNT",
   tiles = {"tnt_top.png", "tnt_bottom.png", "tnt_side.png"},
   groups = {dig_immediate=2, mesecon=2},
   sounds = default.node_sound_wood_defaults(),
   on_punch = function(pos, node, puncher)
      if puncher:get_wielded_item():get_name() == "default:torch" then
         if minetest.get_player_privs(puncher).use_tnt then
            minetest.sound_play("tnt_ignite", {pos=pos})
            minetest.set_node(pos, {name="tnt:tnt_burning"})
            minetest.get_node_timer(pos):start(4)
            return
         else then
            minetest.chat_send_player(puncher, "You don't have the required priv to use tnt.")
            return
         end
      end
   end,
   mesecons = {effector = {action_on = boom}},
}

[afeys]

How to check the biome of a node?

I'm (at least trying to) making a mod which puts content (small buildings, ruins, hidden treasures,....) in the game. But I'd like to put other content in a desert than in a jungle, so I'd like to find out the biome for node at x,y,z.

Is this possible in MineTest? Does anyone have any ideas how to do this?

[Sokomine]

I'm (at least trying to) making a mod which puts content (small buildings, ruins, hidden treasures,....) in the game. But I'd like to put other content in a desert than in a jungle, so I'd like to find out the biome for node at x,y,z.

Maybe you'll be intrested in my mg_villages. It does all the tedious stuff that's necessarry to let placed buildings look well - i.e. blend the terrain, avoid cavegen holes, change the materials randomly etc. It does, however, not react to the sourrounding terrain. Single houses may be located inside one biome, but larger buildings and especially villages will often cover at least two biomes.

[oleastre]

Using mgv5/7 generators, you can simply use register_decoration and specify a list of biomes where your content should be placed (don't know if it works with mgv6).

Another solution is to register an "on_generated" callback with the current mapgen. This will give you a map of the generated nodes and their biome.

[Hybrid Dog]

Hello again i am trying to set up tnt so it will require a priv but it seems to crash

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Code: Select all

minetest.register_node("tnt:tnt", {
   description = "TNT",
   tiles = {"tnt_top.png", "tnt_bottom.png", "tnt_side.png"},
   groups = {dig_immediate=2, mesecon=2},
   sounds = default.node_sound_wood_defaults(),
   on_punch = function(pos, node, puncher)
      if puncher:get_wielded_item():get_name() == "default:torch" then
         if minetest.get_player_privs(puncher).use_tnt then
            minetest.sound_play("tnt_ignite", {pos=pos})
            minetest.set_node(pos, {name="tnt:tnt_burning"})
            minetest.get_node_timer(pos):start(4)
            return
         else then
            minetest.chat_send_player(puncher, "You don't have the required priv to use tnt.")
            return
         end
      end
   end,
   mesecons = {effector = {action_on = boom}},
}

minetest.get_player_privs needs the name of the player (in this case puncher:get_player_name())
same for minetest.chat_send_player

[paramat]

afeys
In mgv5/v7 you can use the 'mapgen object biomemap' (see lua-api.txt) which is available for use in an 'on generated' function.
In mgv6 without the snowbiomes option calculate biome and humidity noise from the parameters:

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#mgv6_np_biome = 0, 1, (250, 250, 250), 9130, 3, 0.50, 2.0
#mgv6_np_humidity = 0.5, 0.5, (500, 500, 500), 72384, 4, 0.66, 2.0

Then:
if biome noise > 0.4 then desert
elseif humidity noise > then jungle
else normal biome

However biome noise has an offset added, so for (x, z) calculate noise at (x + 150, z + 50)

[prestidigitator]

However biome noise has an offset added, so for (x, z) calculate noise at (x + 150, z + 50)

Huh? An arbitrary offset was just added for some reason? That's really screwed up. I hope there's a bugfix request for that....

[Ben]

Is there a way to detect the last modification time of a block, preferable in regards to minetest.get_gametime() or similar?

I'm scanning the nodes in a small area around a central node, and to save time, I'd like to skip previously scanned nodes if "the block hasn't been changed since then". (Bonus question: if this does not make sense, that'd be good to know, too ;-) )

[paramat]

Huh? An arbitrary offset was just added for some reason? That's really screwed up. I hope there's a bugfix request for that....

Mgv6 has lots of offsets, noise often generates patterns that align with (x=0, z=0) or points at noise 'spread' distances from there, so offsets help to break up those alignments. When hmmmm took over mapgen 3 years ago he luckily didn't bother with offsets to keep thing simpler, they are a headache for sure.