Best way to do object collision?

Question

I'm trying to do wall collision for objects and I've followed a tutorial that offers one method of doing collision.

This is the tutorial: https://www.youtube.com/watch?v=yZU1QJJdxgs

Currently, if the object detects a wall, instead of moving it's full distance, it moves pixel by pixel until it's against the wall. This worked well until I started trying to rotate the object with image_rotate, because it caused objects to get stuck in walls by either sliding against them or if they rotated into them.

I fixed this by using draw_sprite_ext instead and changing the rotation of the sprite itself and not the mask, which worked for about 20 minutes until it started causing more problems.

///obj_player Step

//Initialise Variables
hor_speed = 0;
ver_speed = 0;
accelerationspeed = 0.2;
decelerationspeed = 0.2;
maxspeed = 3;
pointdirection = 0;

//Get player's input
key_right = keyboard_check(ord("D"))
key_left = -keyboard_check(ord("A"))
key_up = -keyboard_check(ord("W"))
key_down = keyboard_check(ord("S"))
pointdirection = point_direction(x,y,mouse_x,mouse_y) + 270

hor_movement = key_left + key_right;
ver_movement = key_up + key_down;

//horizontal acceleration
if !(abs(hor_speed) >= maxspeed) {
    hor_speed += hor_movement * accelerationspeed;
}
//horizontal deceleration
if (hor_movement = 0) {
    if !(hor_speed = 0) {
        hor_speed -= (sign(hor_speed) * decelerationspeed)
    }
}

//vertical acceleration
if !(abs(ver_speed) >= maxspeed) {
    ver_speed += ver_movement * accelerationspeed;
}
//vertical deceleration
if (ver_movement = 0) {
    if !(ver_speed = 0) {
        ver_speed -= (sign(ver_speed) * decelerationspeed)
    }
}

//horizontal collision
if (place_meeting(x+hor_speed,y,obj_wall)) {
    while(!place_meeting(x+sign(hor_speed),y,obj_wall)) {
    x += sign(hor_speed);
    }
    hor_speed = 0;
}

//vertical collision
if (place_meeting(x,y+ver_speed,obj_wall)) {
    while(!place_meeting(x,y+sign(ver_speed),obj_wall)) {
    y += sign(ver_speed);
    }
    ver_speed = 0;
}

//move the player
x += hor_speed;
y += ver_speed;

///obj_player Draw
//rotate to look at cursor
draw_sprite_ext(spr_player, 0, x,y,image_xscale,image_yscale, pointdirection, image_blend, image_alpha);

I think the best way to rotate objects is through image_rotate, and I'd like to do it without getting stuff stuck in walls. Can my current method of collision be adapted to do this, or should I attempt to do it in a different way?

Answer 1

Your code looks fine, but if you're going to be rotating objects then you would also need to consider having a "knock back mechanic." Reason being is the player could be sitting next to this wall and if you rotate the object over them so they cant move, its not a fun time being stuck.

So you 'could' have the object that's rotating do a check before rotating and if objects are in the way then either stop it or push them back so they cant be within range.