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List of motion planning grid functions
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mp_grid_create(xstart, ystart, hcells, vcells, cellwidth,
cellheight):
This function generates the empty grid that will be used for path finding
and returns its ID. You will probably create one grid for a room, not one per monster
instance, so the grid might be created by a "controller" instance
 | xstart, ystart are the top left coordinates of the grid |
| hcells, vcells are the size of the grid in cells (not pixels) |
| cellwidth, cellheight is the size in pixels of a cell |
If your maze walls are 32 by 32 blocks you might use:
grid_id=mp_grid_create(0,0,floor(room_width/32),floor(room_height/32),32,32); |
| mp_grid_destroy(grid_id)
Dispose of the grid, if you created the grid in the instance create event
you should dispose of it in the instance destroy event
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| mp_grid_path(grid_id, path_id, xstart, ystart, xgoal, ygoal, allowdiag)
This is the big one, the function that actually solves mazes. It returns
a boolean, true if it succeeded in finding a path. The start and end points
of the path are the points you supply, and the points in between are the
centres of the grid cells the path passes through
| grid_id The grid to be solved |
| path_id The ID of a path generated by path_add (don't use a predefined
path) that will be overwritten with the maze solution |
| xstart,ystart The location you want the path to start from, typically
the location of a monster |
| xgoal,ygoal The location you want the path to end at, typically the
location of the player |
| allowdiag determines if the path can contain diagonal sections,
usually false
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Functions to allow the grid to be manipulated directly
| mp_grid_add_cell(grid_id, h, v) |
| mp_grid_clear_cell(grid_id, h, v) |
| mp_grid_get_cell(grid_id, h , v) |
The above functions work in grid coordinates not room coordinates, and
would be used where you have your own rules for what parts of a room are
passable.
Functions to add room features to the grid
| mp_grid_add_instances(grid_id, obj, prec)
Mark any cells covered or partially covered by instances of obj. If prec
is true then the accurate collision mask will be used otherwise the bounding
box will be used
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| mp_grid_add_rectangle(grid_id, x1, y1, x2, y2)
Mark a rectangle of cells as obstructed using room (not grid) coordinates
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| mp_grid_clear_rectangle(grid_id, x1, y1, x2, y2);
Mark a rectangle of cells as clear using room (not grid) coordinates |
Other functions
| mp_grid_clear_all(grid_id)
Mark the entire grid as clear
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| mp_grid_draw(grid_id)
Draws the grid on screen using red to indicate an obstructed cell and
green to indicate a clear cell. The GMS manual warns that this function
could be slow and should only be used for debugging. |
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