Skip to content
Permalink
Browse files
Improve LuaVoxelManip documentation
  • Loading branch information
kwolekr committed Nov 7, 2015
1 parent 2a12579 commit f9e394a4669e667fcef8992946458c769b4e2770
Show file tree
Hide file tree
Showing 2 changed files with 163 additions and 9 deletions.
@@ -4,6 +4,11 @@
-- Constants values for use with the Lua API
--

-- Built-in Content IDs (for use with VoxelManip API)
core.CONTENT_UNKNOWN = 125
core.CONTENT_AIR = 126
core.CONTENT_IGNORE = 127

-- Block emerge status constants (for use with core.emerge_area)
core.EMERGE_CANCELLED = 0
core.EMERGE_ERRORED = 1
@@ -2812,22 +2812,171 @@ nil, this table will be used to store the result instead of creating a new table
`noisevals = noise:getMapSlice({x=24, z=1}, {x=1, z=1})`

### `VoxelManip`
An interface to the `MapVoxelManipulator` for Lua.

It can be created via `VoxelManip()` or `minetest.get_voxel_manip()`.
The map will be pre-loaded if two positions are passed to either.
#### About VoxelManip
VoxelManip is a scripting interface to the internal 'Map Voxel Manipulator' facility. The purpose of
this object is for fast, low-level, bulk access to reading and writing Map content. As such, setting
map nodes through VoxelManip will lack many of the higher level features and concepts you may be used
to with other methods of setting nodes. For example, nodes will not have their construction and
destruction callbacks run, and no rollback information is logged.

It is important to note that VoxelManip is designed for speed, and *not* ease of use or flexibility.
If your mod requires a map manipulation facility that will handle 100% of all edge cases, or the use
of high level node placement features, perhaps minetest.set_node() is better suited for the job.

In addition, VoxelManip might not be faster, or could even be slower, for your specific use case.
VoxelManip is most effective when setting very large areas of map at once - for example, if only
setting a 5x5x5 node area, a minetest.set_node() loop may be more optimal. Always profile code
using both methods of map manipulation to determine which is most appropriate for your usage.

#### Using VoxelManip
A VoxelManip object can be created any time using either:
`VoxelManip([p1, p2])`, or `minetest.get_voxel_manip([p1, p2])`.

If the optional position parameters are present for either of these routines, the specified region
will be pre-loaded into the VoxelManip object on creation. Otherwise, the area of map you wish to
manipulate must first be loaded into the VoxelManip object using `VoxelManip:read_from_map()`.

Note that `VoxelManip:read_from_map()` returns two position vectors. The region formed by these
positions indicate the minimum and maximum (respectively) positions of the area actually loaded in
the VoxelManip, which may be larger than the area requested. For convenience, the loaded area
coordinates can also be queried any time after loading map data with `VoxelManip:get_emerged_area()`.

Now that the VoxelManip object is populated with map data, your mod can fetch a copy of this data
using either of two methods. `VoxelManip:get_node_at()`, which retrieves an individual node in a
MapNode formatted table at the position requested is the simplest method to use, but also the slowest.

Nodes in a VoxelManip object may also be read in bulk to a flat array table using:
`VoxelManip:get_data()` for node content (in Content ID form, see section 'Content IDs'),
`VoxelManip:get_light_data()` for node light levels, and
`VoxelManip:get_param2_data()` for the node type-dependent "param2" values.

See section 'Flat array format' for more details.

It is very important to understand that the tables returned by any of the above three functions
represent a snapshot of the VoxelManip's internal state at the time of the call. This copy of the
data will *not* magically update itself if another function modifies the internal VoxelManip state.
Any functions that modify a VoxelManip's contents work on the VoxelManip's internal state unless
otherwise explicitly stated.

Once the bulk data has been edited to your liking, the internal VoxelManip state can be set using:
`VoxelManip:set_data()` for node content (in Content ID form, see section 'Content IDs'),
`VoxelManip:set_light_data()` for node light levels, and
`VoxelManip:set_param2_data()` for the node type-dependent "param2" values.

The parameter to each of the above three functions can use any table at all in the same flat array
format as produced by get_data() et al. and is *not required* to be a table retrieved from get_data().

Once the internal VoxelManip state has been modified to your liking, the changes can be committed back
to the map by calling `VoxelManip:write_to_map()`.

Finally, a call to `VoxelManip:update_map()` is required to re-calculate lighting and set the blocks
as being modified so that connected clients are sent the updated parts of map.


##### Flat array format
Let
`Nx = p2.X - p1.X + 1`,
`Ny = p2.Y - p1.Y + 1`, and
`Nz = p2.Z - p1.Z + 1`.

Then, for a loaded region of p1..p2, this array ranges from `1` up to and including the value of
the expression `Nx * Ny * Nz`.

Positions offset from p1 are present in the array with the format of:
```
[
(0, 0, 0), (1, 0, 0), (2, 0, 0), ... (Nx, 0, 0),
(0, 1, 0), (1, 1, 0), (2, 1, 0), ... (Nx, 1, 0),
...
(0, Ny, 0), (1, Ny, 0), (2, Ny, 0), ... (Nx, Ny, 0),
(0, 0, 1), (1, 0, 1), (2, 0, 1), ... (Nx, 0, 1),
...
(0, Ny, 2), (1, Ny, 2), (2, Ny, 2), ... (Nx, Ny, 2),
...
(0, Ny, Nz), (1, Ny, Nz), (2, Ny, Nz), ... (Nx, Ny, Nz)
]
```

and the array index for a position p contained completely in p1..p2 is:

`(p.Z - p1.Z) * Ny * Nx + (p.Y - p1.Y) * Nx + (p.X - p1.X) + 1`

Note that this is the same "flat 3D array" format as `PerlinNoiseMap:get3dMap_flat()`.
VoxelArea objects (see section 'VoxelArea') can be used to simplify calculation of the index
for a single point in a flat VoxelManip array.

##### Content IDs
A Content ID is a unique integer identifier for a specific node type. These IDs are used by VoxelManip
in place of the node name string for `VoxelManip:get_data()` and `VoxelManip:set_data()`. You can use
`minetest.get_content_id()` to look up the Content ID for the specified node name, and
`minetest.get_name_from_content_id()` to look up the node name string for a given Content ID.
After registration of a node, its Content ID will remain the same throughout execution of the mod.
Note that the node being queried needs to have already been been registered.

The following builtin node types have their Content IDs defined as constants:
```
core.CONTENT_UNKNOWN (ID for "unknown" nodes)
core.CONTENT_AIR (ID for "air" nodes)
core.CONTENT_IGNORE (ID for "ignore" nodes)

This comment has been minimized.

Copy link
@HybridDog

HybridDog Nov 7, 2015

Contributor

core is minetest, isn't it?

This comment has been minimized.

Copy link
@rubenwardy

rubenwardy Nov 7, 2015

Member

yeah, this should be minetest.

```

##### Mapgen VoxelManip objects
Inside of `on_generated()` callbacks, it is possible to retrieve the same VoxelManip object used by the
core's Map Generator (commonly abbreviated Mapgen). Most of the rules previously described still apply
but with a few differences:
* The Mapgen VoxelManip object is retrieved using: `minetest.get_mapgen_object("voxelmanip")`
* This VoxelManip object already has the region of map just generated loaded into it; it's not necessary
to call `VoxelManip:read_from_map()` before using a Mapgen VoxelManip.
* The `on_generated()` callbacks of some mods may place individual nodes in the generated area using
non-VoxelManip map modification methods. Because the same Mapgen VoxelManip object is passed through
each `on_generated()` callback, it becomes necessary for the Mapgen VoxelManip object to maintain
consistency with the current map state. For this reason, calling any of the following functions:
`minetest.add_node()`, `minetest.set_node()`, or `minetest.swap_node()`
will also update the Mapgen VoxelManip object's internal state active on the current thread.
* After modifying the Mapgen VoxelManip object's internal buffer, it may be necessary to update lighting
information using either: `VoxelManip:calc_lighting()` or `VoxelManip:set_lighting()`.
* `VoxelManip:update_map()` does not need to be called after `write_to_map()`. The map update is performed
automatically after all on_generated callbacks have been run for that generated block.

##### Other API functions operating on a VoxelManip
If any VoxelManip contents were set to a liquid node, `VoxelManip:update_liquids()` must be called
for these liquid nodes to begin flowing. It is recommended to call this function only after having
written all buffered data back to the VoxelManip object, save for special situations where the modder
desires to only have certain liquid nodes begin flowing.

The functions `minetest.generate_ores()` and `minetest.generate_decorations()` will generate all
registered decorations and ores throughout the full area inside of the specified VoxelManip object.

`minetest.place_schematic_on_vmanip()` is otherwise identical to `minetest.place_schematic()`,
except instead of placing the specified schematic directly on the map at the specified position, it
will place the schematic inside of the VoxelManip.

##### Notes
* Attempting to read data from a VoxelManip object before map is read will result in a zero-length
array table for `VoxelManip:get_data()`, and an "ignore" node at any position for
`VoxelManip:get_node_at()`.
* If either a region of map has not yet been generated or is out-of-bounds of the map, that region is
filled with "ignore" nodes.
* Other mods, or the core itself, could possibly modify the area of map currently loaded into a VoxelManip
object. With the exception of Mapgen VoxelManips (see above section), the internal buffers are not
updated. For this reason, it is strongly encouraged to complete the usage of a particular VoxelManip
object in the same callback it had been created.
* If a VoxelManip object will be used often, such as in an `on_generated()` callback, consider passing
a file-scoped table as the optional parameter to `VoxelManip:get_data()`, which serves as a static
buffer the function can use to write map data to instead of returning a new table each call. This
greatly enhances performance by avoiding unnecessary memory allocations.

#### Methods
* `read_from_map(p1, p2)`: Reads a chunk of map from the map containing the
region formed by `p1` and `p2`.
* `read_from_map(p1, p2)`: Loads a chunk of map into the VoxelManip object containing
the region formed by `p1` and `p2`.
* returns actual emerged `pmin`, actual emerged `pmax`
* `write_to_map()`: Writes the data loaded from the `VoxelManip` back to the map.
* **important**: data must be set using `VoxelManip:set_data` before calling this
* **important**: data must be set using `VoxelManip:set_data()` before calling this
* `get_node_at(pos)`: Returns a `MapNode` table of the node currently loaded in
the `VoxelManip` at that position
* `set_node_at(pos, node)`: Sets a specific `MapNode` in the `VoxelManip` at
that position
* `get_data(buffer)`: Gets the data read into the `VoxelManip` object
* `set_node_at(pos, node)`: Sets a specific `MapNode` in the `VoxelManip` at that position
* `get_data([buffer])`: Retrieves the node content data loaded into the `VoxelManip` object
* returns raw node data in the form of an array of node content IDs
* if the param `buffer` is present, this table will be used to store the result instead
* `set_data(data)`: Sets the data contents of the `VoxelManip` object

0 comments on commit f9e394a

Please sign in to comment.