ground_place_pattern

/// @description ground_place_pattern(ground_grid)
/// @param ground_grid

var _grid   = argument0;

var _w      = ds_grid_width(_grid);
var _h      = ds_grid_height(_grid);

var _brush_circle = 0;
var _brush_square = 1;
var _brush_random = 2;
var _brush_type   = _brush_square;

var _num_strokes = 4 * floor(sqrt(_w * _h));
var _n = 0;
var _brush;

for(;_n<_num_strokes;++_n){

    var _i = irandom(_w);
    var _j = irandom(_h);

    var _brush_size = 2;

    var _ctr = floor(_brush_size / 2);

    var _bx, _by;

    for(_bx=0;_bx<_brush_size;++_bx)
        for(_by=0;_by<_brush_size;++_by)
            if(_brush_type == _brush_square)
                _brush[_bx, _by] = true;
            else if (_brush_type == _brush_circle)
                _brush[_bx, _by] = point_distance(_ctr,_ctr,_bx,_by) <= (_ctr-1) ? 1 : 0;
            else if (_brush_type == _brush_random)
                _brush[_bx, _by] = choose(true,false);

    // wander

    var _iterations = 1 + irandom(3);
    var _t = 0;

    for(;_t<_iterations;++_t){

        _i += irandom_range(-1,1);
        _j += irandom_range(-1,1);

        // place patches according to brush

        for(_bx=0;_bx<_brush_size;++_bx){
            for(_by=0;_by<_brush_size;++_by){

                if(_brush[_bx, _by]){

                    var _x = _i +_bx;
                    var _y = _j +_by;

                    if(_x < 0 || _x >= _w
                    || _y < 0 || _y >= _h)
                        continue;

                    _grid[# _x, _y] = 1;
                }
            }
        }
    }
}