Prototyping - Gameplay Map Programming

We have to modify the map files and bring them in to GameMaker using text reads for HTML5 compatability. While reading the files, we'll create both the sprite map and a collision map based on the values. We'll test the map drawing both with and without VRAM.

Objects

We can implement the world and view using two objects:

Concept	Object	Notes
Map display	obj_map	Loads and holds data for the scene. Spawns child objects as necessary
Camera	obj_camera	Displays a text-only line in large font centered on the screen

C Code

We have to convert all of the map files from the original traffic department to a format that's safe for ASCII / UTF8 reads. Since all map files have a maximum byte value of 80, we have plenty of room to move byte values up in to a valid range.

NEWMAP.c:

/* Shifts the values of the original Traffic Department 2192 MAPs up 0x20
*/

#include <stdio.h>
#include <string.h>
#include <stdint.h>

int main(int argc, char* argv[])
{
	uint8_t FILENAME_LEN;
	char fname_out[12];
	FILE *fin;
	FILE *fout;
	uint16_t current_byte;
	
	/* Make output file based on input file name */
	FILENAME_LEN = strlen(argv[1]);					/* Length of Input File Name */
	strncpy(fname_out, argv[1], FILENAME_LEN-3);	/* Remove extension */
	fname_out[FILENAME_LEN-3]='\0';					/* Nullterm it */
	strncat(fname_out, "MP2", 3);					/* Attach new extension */
	
	/* Open Files */
	fin = fopen(argv[1], "rb");
	fout = fopen(fname_out, "wb");
	
	/* Process byte stream */
	for (current_byte=0; current_byte<40401; current_byte++)
	{
		fputc((fgetc(fin)+0x20), fout);
		fputc('\r', fout);
		fputc('\n', fout);
	}
	
	/* Close files */
	fclose(fin);
	fclose(fout);
	
	return 0;
}

/* Shifts the values of the original Traffic Department 2192 MAPs up 0x20

#include <stdio.h>

#include <string.h>

#include <stdint.h>

int main(int argc, char* argv[])

{

uint8_t FILENAME_LEN;

char fname_out[12];

FILE *fin;

FILE *fout;

uint16_t current_byte;

/* Make output file based on input file name */

FILENAME_LEN = strlen(argv[1]); /* Length of Input File Name */

strncpy(fname_out, argv[1], FILENAME_LEN-3); /* Remove extension */

fname_out[FILENAME_LEN-3]='\0'; /* Nullterm it */

strncat(fname_out, "MP2", 3); /* Attach new extension */

/* Open Files */

fin = fopen(argv[1], "rb");

fout = fopen(fname_out, "wb");

/* Process byte stream */

for (current_byte=0; current_byte<40401; current_byte++)

{

fputc((fgetc(fin)+0x20), fout);

fputc('\r', fout);

fputc('\n', fout);

}

/* Close files */

fclose(fin);

fclose(fout);

return 0;

}

GML Code

We do our GameMaker work in GML for each object and event

obj_map: Create 1

Set a reference to the gamedata object

///Set reference
gamedata = instance_find(obj_currentgame,0)

1 2	///Set reference gamedata = instance_find(obj_currentgame,0)

obj_map: Create 2

Initialize variables for map size, draw trigger, and draw mode

///Init vars
new_surface = true
map_width = 201
map_height = 201

draw_mode = 1 /* 0 = slowest (no VRAM), 1 = fastest (VRAM hog)

///Init vars

new_surface = true

map_width = 201

map_height = 201

draw_mode = 1 /* 0 = slowest (no VRAM), 1 = fastest (VRAM hog)

obj_map: Create 3

Create the data structures

///Create data structures
mapdata = ds_grid_create(map_width, map_height)
collision_map = ds_grid_create(map_width, map_height)
map_surface = 0

if draw_mode == 1 then
    map_surface = surface_create(map_width*32, map_height*32)

///Create data structures

mapdata = ds_grid_create(map_width, map_height)

collision_map = ds_grid_create(map_width, map_height)

map_surface = 0

if draw_mode == 1 then

map_surface = surface_create(map_width*32, map_height*32)

obj_map: Create 4

Load the map data from our ASCII-safe files. We'll also create the collision map for certain sprites

///Load map data
var file, map_char;

file = file_text_open_read("TD.MP2")

/* read map in column major */

for (var xx=0; xx < map_width; xx++)
{
    for (var yy=0; yy < map_height; yy++)
    {
        map_char = file_text_read_string(file);
        ds_grid_set(mapdata, xx, yy, ord(map_char)-$20)
        switch ord(map_char)-$20
        {
            case $31:
            case $32:
            case $33:
            case $38:
            case $39:
            case $45:
            case $3B:
            case $3C:
            case $3D: ds_grid_set(collision_map, xx, yy, 0); break;
            default: ds_grid_set(collision_map, xx, yy, 1); break;
        }
        file_text_readln(file)
    }
}
file_text_close(file)

///Load map data

var file, map_char;

file = file_text_open_read("TD.MP2")

/* read map in column major */

for (var xx=0; xx < map_width; xx++)

{

for (var yy=0; yy < map_height; yy++)

{

map_char = file_text_read_string(file);

ds_grid_set(mapdata, xx, yy, ord(map_char)-$20)

switch ord(map_char)-$20

{

case $31:

case $32:

case $33:

case $38:

case $39:

case $45:

case $3B:

case $3C:

case $3D: ds_grid_set(collision_map, xx, yy, 0); break;

default: ds_grid_set(collision_map, xx, yy, 1); break;

}

file_text_readln(file)

}

file_text_close(file)

obj_map: Destroy 1

Release all data structures

///Free data structures
ds_grid_destroy(mapdata)
ds_grid_destroy(collision_map)
surface_free(map_surface)

///Free data structures

ds_grid_destroy(mapdata)

ds_grid_destroy(collision_map)

surface_free(map_surface)

obj_map: Draw 1

The RAM only drawing of the map (slow)

///Draw entire map each frame (slowest)
if draw_mode == 0 then
{
    var xx, yy, spr;
    
    for (yy=0; yy < map_height; yy++)
    {
        for (xx=0; xx < map_width; xx++)
        {
            spr = ds_grid_get(mapdata, xx, yy)
            draw_sprite(BLK1, spr, xx*32, yy*32)
        }
    }
}

///Draw entire map each frame (slowest)

if draw_mode == 0 then

{

var xx, yy, spr;

for (yy=0; yy < map_height; yy++)

{

for (xx=0; xx < map_width; xx++)

{

spr = ds_grid_get(mapdata, xx, yy)

draw_sprite(BLK1, spr, xx*32, yy*32)

}

obj_map: Draw 2

Storing the map in VRAM method (fast)

///Draw map from VRAM surface (fastest)
if draw_mode == 1
{
    if !surface_exists(map_surface)
        new_surface = true
    
    if new_surface
    {
        surface_set_target(map_surface)
        draw_set_alpha(1)
        var xx, yy, spr;
        
        for (yy=0; yy < map_height; yy++)
        {
            for (xx=0; xx < map_width; xx++)
            {
                spr = ds_grid_get(mapdata, xx, yy)
                draw_sprite(BLK1, spr, xx*32, yy*32)
            }
        }
        surface_reset_target()
        new_surface = false
    }
    draw_set_alpha(1)
    draw_surface(map_surface,0,0)
}

///Draw map from VRAM surface (fastest)

if draw_mode == 1

{

if !surface_exists(map_surface)

new_surface = true

if new_surface

{

surface_set_target(map_surface)

draw_set_alpha(1)

var xx, yy, spr;

for (yy=0; yy < map_height; yy++)

{

for (xx=0; xx < map_width; xx++)

{

spr = ds_grid_get(mapdata, xx, yy)

draw_sprite(BLK1, spr, xx*32, yy*32)

}

surface_reset_target()

new_surface = false

}

draw_set_alpha(1)

draw_surface(map_surface,0,0)

}

obj_camera: Create 1

///Register self and references
keyboard_register(id)

gamedata = instance_find(obj_currentgame,0)

///Register self and references

keyboard_register(id)

gamedata = instance_find(obj_currentgame,0)

obj_camera: Create 2

Variables and other properties. The most important is the camera target, which we can lock to anything. For now, we'll lock it to itself

///Init vars
camera_target = id
map_x = 0
map_y = 0

//camera properties
x = room_width/2
y = room_height/2
view_object[0] = id
view_wview[0] = 320
view_hview[0] = 200
view_hborder[0] = view_wview[0]/2
view_vborder[0] = view_hview[0]/2

///Init vars

camera_target = id

map_x = 0

map_y = 0

//camera properties

x = room_width/2

y = room_height/2

view_object[0] = id

view_wview[0] = 320

view_hview[0] = 200

view_hborder[0] = view_wview[0]/2

view_vborder[0] = view_hview[0]/2

obj_camera: Destroy 1

Remove keyboard

///Deregister
keyboard_deregister(id)

1 2	///Deregister keyboard_deregister(id)

obj_camera: Step 1

Process input commands. Camera only responds to controls when it's not locked to another object

///Process commands
while !ds_stack_empty(command_stack)
{
    var cmd = ds_stack_pop(command_stack)
    
    switch cmd
    {
        case "hold_left": x-=10; break;
        case "hold_right": x+=10; break;
        case "hold_up": y-=10; break;
        case "hold_down": y+=10; break;
        case "push_x": 
        {
            if zoom_out == zoom_in
                zoom_out = true
        } break;
        case "push_z": 
        {
            if zoom_out == zoom_in
                zoom_in = true
        } break;
    }
}

///Process commands

while !ds_stack_empty(command_stack)

{

var cmd = ds_stack_pop(command_stack)

switch cmd

{

case "hold_left": x-=10; break;

case "hold_right": x+=10; break;

case "hold_up": y-=10; break;

case "hold_down": y+=10; break;

case "push_x":

{

if zoom_out == zoom_in

zoom_out = true

} break;

case "push_z":

{

if zoom_out == zoom_in

zoom_in = true

} break;

}

obj_camera: End Step 1

Lock camera to target

///Lock camera to target
if instance_exists(camera_target)
{
    x = camera_target.x
    y = camera_target.y
}

///Lock camera to target

if instance_exists(camera_target)

{

x = camera_target.x

y = camera_target.y

}

obj_camera: Room Start 1

Find the player's ship

///Lock camera to player
camera_target = id

1 2	///Lock camera to player camera_target = id

< Part 23 – Mission Gameplay Design	Part 25 – Ship Actions >