Week 12, Collision improvement

This week, I tried to understand why it was still possible to stuck the player inside the map. Especially when falling back to the ground with a 45 degree angle.

The collision management in html5 game

My current collision management is done in two different steps.

1. Check collisions in x direction
2. Check collisions in y direction

Hey why did I not checked both together ? Because then the entities cannot move anymore as there is always an acceleration in y direction, that's Gravity !

see below a the code which explains the different steps :

//store the current position
StoredcollisionRect.x = collisionRect.x;
//update the collision boundaries with the acceleration in x direction
collisionRect.x += MovableEntities[x].dx;
//check collision and if true, put the acceleration to 0, stops the movement
if(collision) MovableEntities[x].dx = 0;

//get back to current position
collisionRect.x = StoredcollisionRect.x;
//Then do exactly the same in y direction
//At the end, update player position only one time in both x and y direction

The collision issue at 45 degree

The issue is that this collision detection algorithm cannot work if the player has a 45 degree angle.

In that special case the collision detection is blind in x and in y direction, the following tick, the player will collide to the ground and stay blocked.

To remove that potential issue, we will add a third check with both directions only when the first two collision checks failed.

if(no_collision_in_x_or_y) {
    collisionRect.x += MovableEntities[x].dx;
    collisionRect.y += MovableEntities[x].dy;
    if(collision) MovableEntities[x].dy = 0; //priority to y direction 
}

In such case, I gave the priority to y direction, that will help the player not to die if he gets right on the side of a block

Bonus.. bullets

I added this week some bullets when you press on action area or spacebar. It's a specific Movable entity which can collide to everything but this has still to be coded. So far the bullet just go through the screen.

I will now work on AI management, it may takes some weeks before it works ! You can always try the latest version of the html5 game.

Let's code!