Add support for NoiseParams in minetest.get_perlin() and add docs on NoiseParams to lua_api.txt

doc/lua_api.txt

@@ -482,23 +482,65 @@ A box of a regular node would look like:
 
 type = "leveled" is same as "fixed", but y2 will be automatically set to level from param2
 
+
 Meshes
 -----------
 If drawtype "mesh" is used tiles should hold model materials textures.
 Only static meshes are implemented.
 For supported model formats see Irrlicht engine documentation.
-    
+
+
+Noise Parameters
+--------------------
+Noise Parameters, or commonly called NoiseParams, define the properties of perlin noise.
+ - offset
+    Offset that the noise is translated by (i.e. added) after calculation.
+ - scale
+    Factor that the noise is scaled by (i.e. multiplied) after calculation.
+ - spread
+    Vector containing values by which each coordinate is divided by before calculation.
+    Higher spread values result in larger noise features.
+    A value of {x=250, y=250, z=250} is common.
+ - seed
+    Random seed for the noise.  Add the world seed to a seed offset for world-unique noise.
+    In the case of minetest.get_perlin(), this value has the world seed automatically added.
+ - octaves
+    Number of times the noise gradient is accumulated into the noise.
+    Increase this number to increase the amount of detail in the resulting noise.
+    A value of 6 is common.
+ - persistence
+    Factor by which the effect of the noise gradient function changes with each successive octave.
+    Values less than 1 make the details of successive octaves' noise diminish, while values
+    greater than 1 make successive octaves stronger.
+    A value of 0.6 is common.
+ - lacunarity
+    Factor by which the noise feature sizes change with each successive octave.
+    A value of 2.0 is common.
+ - flags
+    Leave this field unset for no special handling.
+    Currently supported are:
+    - defaults
+       Specify this if you would like to keep auto-selection of eased/not-eased while specifying
+       some other flags.
+    - eased
+       Maps noise gradient values onto a quintic S-curve before performing interpolation.
+       This results in smooth, rolling noise.  Disable this for sharp-looking noise.
+       If no flags are specified (or defaults is), 2D noise is eased and 3D noise is not eased.
+    - absvalue
+       Accumulates the absolute value of each noise gradient result.
+
+
 Ore types
 ---------------
 These tell in what manner the ore is generated.
 All default ores are of the uniformly-distributed scatter type.
 
-- scatter
+ - scatter
     Randomly chooses a location and generates a cluster of ore.
     If noise_params is specified, the ore will be placed if the 3d perlin noise at
     that point is greater than the noise_threshold, giving the ability to create a non-equal
     distribution of ore.
-- sheet
+ - sheet
     Creates a sheet of ore in a blob shape according to the 2d perlin noise described by noise_params.
     The relative height of the sheet can be controlled by the same perlin noise as well, by specifying
     a non-zero 'scale' parameter in noise_params.  IMPORTANT: The noise is not transformed by offset or
@@ -506,10 +548,11 @@ All default ores are of the uniformly-distributed scatter type.
     The height of the blob is randomly scattered, with a maximum height of clust_size.
     clust_scarcity and clust_num_ores are ignored.
     This is essentially an improved version of the so-called "stratus" ore seen in some unofficial mods.
-- claylike - NOT YET IMPLEMENTED
+ - claylike - NOT YET IMPLEMENTED
     Places ore if there are no more than clust_scarcity number of specified nodes within a Von Neumann
     neighborhood of clust_size radius.
 
+
 Ore attributes
 -------------------
 See section Flag Specifier Format.
@@ -534,6 +577,7 @@ The default value is simple, and is currently the only type supported.
     probability of a node randomly appearing when placed.  This decoration type is intended to be used
     for multi-node sized discrete structures, such as trees, cave spikes, rocks, and so on.
 
+
 Schematic specifier
 --------------------
     A schematic specifier identifies a schematic by either a filename to a Minetest Schematic file (.mts)
@@ -552,6 +596,7 @@ When passed to minetest.create_schematic, probability is an integer value rangin
 
 Important note: Node aliases cannot be used for a raw schematic provided when registering as a decoration.
 
+
 Schematic attributes
 ---------------------
 See section Flag Specifier Format.
@@ -563,6 +608,7 @@ Currently supported flags:  place_center_x, place_center_y, place_center_z
  - place_center_z
     Placement of this decoration is centered along the Z axis.
 
+
 HUD element types
 -------------------
 The position field is used for all element types.
@@ -1529,6 +1575,7 @@ minetest.find_node_near(pos, radius, nodenames) -> pos or nil
 ^ nodenames: e.g. {"ignore", "group:tree"} or "default:dirt"
 minetest.find_nodes_in_area(minp, maxp, nodenames) -> list of positions
 ^ nodenames: e.g. {"ignore", "group:tree"} or "default:dirt"
+minetest.get_perlin(noiseparams)
 minetest.get_perlin(seeddiff, octaves, persistence, scale)
 ^ Return world-specific perlin noise (int(worldseed)+seeddiff)
 minetest.get_voxel_manip()
@@ -2109,8 +2156,8 @@ methods:
                   implementation making bad distribution otherwise.
 
 PerlinNoise: A perlin noise generator
-- Can be created via PerlinNoise(seed, octaves, persistence, scale)
-- Also minetest.get_perlin(seeddiff, octaves, persistence, scale)
+- Can be created via PerlinNoise(seed, octaves, persistence, scale) or PerlinNoise(noiseparams)
+- Also minetest.get_perlin(seeddiff, octaves, persistence, scale) or minetest.get_perlin(noiseparams)
 methods:
 - get2d(pos) -> 2d noise value at pos={x=,y=}
 - get3d(pos) -> 3d noise value at pos={x=,y=,z=}