collision.rs

// http://recordit.co/LKXWw6hvLK
// player *snaps* to top y of bottom right block when jumping on right wall (and same for left wall, snaps to bottom left top y).
// when player hits top or bottom half of block from the side, it snaps to the the top or bottom of the block relatively.

pub fn collides<F: Point>(a: &AABB<F>, b: &AABB<F>) -> bool {
    return na::partial_lt(a.mins(), b.maxs()) &&
           na::partial_gt(a.maxs(), b.mins());
}

let mut y_diff = player.velocity.y * args.dt;
let mut x_diff = player.velocity.x * args.dt;

let mut player_translation = Vector2::new(x_diff, y_diff);
let mut future_player_bounds = player.get_bounding_box().append_translation(&player_translation);

if future_player_bounds.mins().x < 0.0 {
    player_translation = Vector2::new(0.0, 0.0);
    player_translation.x = -(player.position.x + x_diff);
    future_player_bounds.append_translation_mut(&player_translation);
}

for point in get_surrounding_points(&future_player_bounds) {
    let block_res = self.blocks.get_mut(&Vector2::new(point[0], point[1]));
    if block_res.is_some() {
        let block = block_res.unwrap();
        let block_bounds = block.get_bounding_box();

        if collides(&block_bounds, &future_player_bounds) {
            player_translation = Vector2::new(0.0, 0.0);

            // calculate the difference between centers
            let x_diff = block_bounds.center().x - future_player_bounds.center().x;
            let y_diff = block_bounds.center().y - future_player_bounds.center().y;

            if y_diff.abs() > x_diff.abs() {
                if y_diff > 0.0 {
                    // Top side of entity
                    player_translation.y += block_bounds.mins().y - future_player_bounds.maxs().y;
                    // set blue color overlay
                    block.color = [0.0, 0.0, 1.0, 1.0];
                } else {
                    // Bottom side of entity
                    player.jumping = false;
                    player_translation.y -= future_player_bounds.mins().y - block_bounds.maxs().y;
                    // set red color overlay
                    block.color = [1.0, 0.0, 0.0, 1.0];
                }
            } else {
                if x_diff > 0.0 {
                    // Right side of entity
                    player_translation.x += block_bounds.mins().x - future_player_bounds.maxs().x;
                    // set light green color overlay
                    block.color = [0.5, 1.0, 0.5, 1.0];
                } else {
                    // Left side of entity
                    player_translation.x -= future_player_bounds.mins().x - block_bounds.maxs().x;
                    // set green color overlay
                    block.color = [0.0, 1.0, 0.5, 1.0];
                }
            }

            future_player_bounds.append_translation_mut(&player_translation);
        } else {
            block.color = [0.5, 0.5, 0.9, 1.0];
        }
    }
}

player.position.y = future_player_bounds.mins().y;
player.position.x = future_player_bounds.mins().x;