#summary Drawing maps with Lua.

= Drawing Maps With Lua =

Starting in 0.9.18 it is possible to reliably use drawn map mode to draw maps with scripts.

A simple example is given below.  Note that Drawn maps use an area of 4096x2048.  The examples below are static, but obviously this could be used for a random map variation - for example, simulating the Cave map by doing the fill below, then drawing random tunnels using circles that shift their course smoothly.

= Details =

First, a couple of convenience functions for drawing to the map.

<code lang="lua">

PointsBuffer = ''  -- A string to accumulate points in

function AddPoint(x, y, width, erase)

    PointsBuffer = PointsBuffer .. string.char(band(x,0xff00) / 256 , band(x,0xff) , band(y,0xff00) / 256 , band(y,0xff))

    if width then

        width = bor(width,0x80)

        if erase then

            width = bor(width,0x40)

        end

        PointsBuffer = PointsBuffer .. string.char(width)

    else

        PointsBuffer = PointsBuffer .. string.char(0)

    end

    if #PointsBuffer > 245 then

        ParseCommand('draw '..PointsBuffer)

        PointsBuffer = ''

    end

end

function FlushPoints()

    if #PointsBuffer > 0 then

        ParseCommand('draw '..PointsBuffer)

        PointsBuffer = ''

    end

end

</code>

AddPoint takes an x and y location for the point, a width (indicates the start of a new line) and erase (whether the line is erasing from the map).  The width calculation is described in [DrawnMapFormat].

FlushPoints writes out any values from PointsBuffer that have not already been sent to the engine.

It would be called at the end of a drawing session.

A simple example below.

<code lang="lua">

function onGameInit()

    MapGen = 2

    TemplateFilter = 0

    AddPoint(100,100,10)

    AddPoint(2000,2000)

    AddPoint(2000,100,10)

    AddPoint(100,2000)

    AddPoint(1000,1000,63,true)

    AddPoint(1000,1000,20)

    for i = 63,2,-4 do

        AddPoint(2000,1000,i)

        AddPoint(2000,1000,i-2,true)

    end

    for i = 1,2000,50 do

        AddPoint(i+2000,2000,1)

        AddPoint(4000,2000-i)

    end

    AddPoint(2000,2000,1)

    AddPoint(4000,2000)

    AddPoint(4000,0,1)

    AddPoint(4000,2000)

    FlushPoints()

end

</code>

The first set of AddPoints draws a large X and erases the centre.

The following loop draws a set of nested points, alternating erasure and fill, which results in a set of concentric circles.

The 2nd loop draws a web of lines and frames it using some final AddPoints.

<a href="http://m8y.org/hw/draw1.jpeg">screenshot here</a>

Another brief example.

<code lang="lua">

    for i = 200,2000,600 do

        AddPoint(1,i,63)

        AddPoint(4000,i)

    end

    for i = 500,3500,1000 do

        AddPoint(i,1000,63,true)

    end

    FlushPoints()

</code>

This one fills the map with solid land, and draws 4 circular erased points in it.

<a href="http://m8y.org/hw/draw2.jpeg">screenshot here</a>