Hello,

I making this topic because someone told me in the other threads to just make it a new one. First I am going to post my code and then talk.

typedef struct HITBOX
{
	/* This is for the hitbox's dimensions */
	int x, y;
	int w, h;
	/* This is for pixel perfect collision */
	int surface_n;
	int surface_e;
	int surface_s;
	int surface_w;
} HITBOX;

int collision( HITBOX A, HITBOX B ) {
	int a_left, a_right, a_top, a_bottom;
	a_left = A.x;
	a_right = A.x + A.w;
	a_top = A.y;
	a_bottom = A.y + A.h;

	int b_left, b_right, b_top, b_bottom;
	b_left = B.x;
	b_right = B.x + B.w;
	b_top = B.y;
	b_bottom = B.y + B.h;

	if( a_bottom <= b_top || a_top >= b_bottom || a_right <= b_left || a_left >= b_right ) {
		return false;
	} else {
		return true;
	}
}
int t = 0;
HITBOX TILE;
int world_collision( HITBOX A ) {
	for( t = 0; t < total_tiles; t++ ) {
		TILE.x = levelbox[t].x;
		TILE.y = levelbox[t].y;
		TILE.w = levelbox[t].w;
		TILE.h = levelbox[t].h;
		if( collision( A, TILE ) == true ) {
			A.surface_n = TILE.y;
			A.surface_e = TILE.x + TILE.w;
			A.surface_s = TILE.y + TILE.h;
			A.surface_w = TILE.x;
			return true;
		}
	}
	return false;
}

int collision_lua( lua_State *L ) {
	if( strcmp(lua_tostring(L, 1), "world") == 0 )
		return world_collision( player.hitbox );
	return 0;
}

My collisions technically are pixel perfect, but because the game object inside the lua file moves at a float (although I have done the rounding method to prevent that, I still get the player hovering or inside by 1/2 pixels time to time). I came up with the surface variables inside HITBOX so that when there is a collision (with the level), the hitbox will touch that surface, and i won't see any floating/sinking. The problem is I can't figure out how to return those surface variables easily. I was asking some people, and they told me to do

int world_collision( HITBOX *A ) {
	for( t = 0; t < total_tiles; t++ ) {
		TILE.x = levelbox[t].x;
		TILE.y = levelbox[t].y;
		TILE.w = levelbox[t].w;
		TILE.h = levelbox[t].h;
		if( collision( A, TILE ) == true ) {
			A->surface_n = TILE.y;
			A->surface_e = TILE.x + TILE.w;
			A->surface_s = TILE.y + TILE.h;
			A->surface_w = TILE.x;
			return true;
		}
	}
	return false;
}

I will get the errors:

actor.c: In function 'world_collision':
actor.c:72:3: error: incompatible type for argument 1 of 'collision'
actor.c:45:5: note: expected 'HITBOX' but argument is of type 'struct HITBOX *'
actor.c: In function 'collision_lua':
actor.c:104:3: error: incompatible type for argument 1 of 'world_collision'
actor.c:66:5: note: expected 'struct HITBOX *' but argument is of type 'HITBOX'

although if I change one line to:

if( collision( *A, TILE ) == true ) {

I just get the errors in function 'collision_lua'. If I do:

return world_collision( *player.hitbox );

I will get the issue:

actor.c: In function 'collision_lua':
actor.c:104:27: error: invalid type argument of unary '*' (have 'HITBOX')

Does anybody have any ideas what thing needs changed, and willing to show me? Thanks

ANSI C does not allow you to initialize a variable inside a for statement, or at the very least my GCC compiler won't. Will try defining TILE inside it though, doesn't that make a bunch of them or are they cleared from memory?

EDIT:

thanks, it works

Also, just for the record: What you are doing is NOT pixel perfect collision, it is bounding box collision. Unless every object in your world is a rectangle.

It should if you specify -std=c99.

That's not ANSI C anymore though (admittedly GCC's default setting isn't either, but some gnu89 variant).

Why on earth would anyone be using strictly ANSI C in 2014? Stuck with Turbo C 2.0 or something?