Jono Shields

Detecting Map Tiles


GBAGameJam - Day 12

Okay. I did it!

I figured out how to get map data so I can start using tile data to figure out collisions.

So as before. We have our bg that we made..

bn::affine_bg_ptr map_bg = bn::affine_bg_items::map.create_bg(256, 256);

And I finally found out that you can call to get the pointer to the cells of the map. You can then call .value() on it to get the actual data in a span (kind of like an array?).

So we can use to get the cells and at(x) to get the cell at x. The map cells are a 1d array organised like this...

1 2 3
4 5 6
7 8 9

So I made a helper method to get the cell number of an x and y co-ord. Which ends up being something like this..

bn::fixed get_map_index(bn::fixed tile_x, bn::fixed tile_y, bn::fixed columns)
    return (tile_y * columns) + tile_x;

IMPORTANT NOTE : My actual code is not this pretty.

So now I am just logging the tile at my sprites co-ordinates, which works surprisingly well considering it isn't optimized at all and I have no idea what I am doing.

This will be the basis of collisions and I have a little hacky plan for making it easier for myself, but I will share it later.

I also took the time to add some text to show the current tile my player is over. The examples are really good for this.

For this I needed all of these..

#include "bn_string_view.h"
#include "bn_vector.h"
#include "bn_sprite_text_generator.h"

Plus the sprite font from the example... variable_8x16_sprite_font

And then the following..

// make a text generator using the font supplied, you can use your own images for your own font if you want
bn::sprite_text_generator text_generator(variable_8x16_sprite_font);

// sets the text horizontally in the centre

// make a vector to store pointers to the sprites we are using
bn::vector<bn::sprite_ptr, 32> text_sprites;

// and then in our loop..

while (true)
    // clear the previous frames text

    // generate the new text
    text_generator.generate(0, -40, currentCell, text_sprites);


Pretty happy with what I have acheived today. Can rest easy tonight.

Oh. Also todays tag -> day-12

OMG. Almost forgot the most important thing. I learned how to cast integers to strings.


And tonight I have homework reading the following about pointers...

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