Forums » Help » box2d: player.standing

player.standing is working in standard Impact engine.
Do you know how to implement it when i use box2d ?

i mean there is
## handleMovementTrace: function( res ) {this.standing = false; ...} ##
in default ImpactJS. So, how to do the same in box2d? cause it has it's own collision model

From the Box2D Plugin Thread:

update: function() {
    // Iterate over all contact edges for this body. m_contactList is 
    // a linked list, not an array, hence the "funny" way of iterating 
    // over it
    for( var edge = this.body.m_contactList; edge; edge = edge.next ) {
        
        // Get the normal vector for this contact
        var normal = edge.contact.m_manifold.normal;
        
        // If the normal vector for this contact is pointing upwards
        // (y is less than 0), then this body is "standing" on something
        if( normal.y < 0 ) {
            console.log( 'standing!' );
        }                
    }
    
    …
}

wow, man. thank you a lot!!

I think there's a bug in Box2D, not sure, but basically it goes like this:

If you are up against a wall, (say, to your sprite's right) the normal vector will rapidly toggle between:

(0, -1) - normal vector pointing up out of the floor

and

(-1, 0) - normal vector pointing out of the wall

Additionally, when standing on another Box2d object, the normal vector is (0, 1), which seems wrong to me.

If I figure out a solution I'll update this thread. Dominic's code is a great start but I'm finding a few edge cases where the physics engine is reporting strange data that needs to be handled.

The code here appears to be a bit outdated when using the latest version of the Box2d plugin. This thread being two years old, I'm sure it was bound to happen ;)

The following line

var normal = edge.contact.m_manifold.normal;

There isn't a normal property of b2Manifold. What should we be checking against instead?

I'm using the m_localPlaneNormal property, but the results of the contact edges aren't consistent; normal.y returns 1 when my entity is clearly standing on the collision map. This seems to relate to what tom reported. Curious is anyone figured it out?

Hi all!

I'm using the following code to define player standing :

 for (var edge = this.body.m_contactList;
                                edge; edge = edge.next) {
                            if (!edge.contact.IsTouching()) {
                                continue;
                            }
                            var normal = edge.contact.m_manifold.m_localPlaneNormal;
                            if (normal.y < 0) {
                                return true;
                            }
                        }
                        return false;
                    }

I have a level with crates. When i jump on the one of the crates player.stading = true but when i turn the crate on the other side ( during the game) and jump on it once more i get player.standing = false .

Would appreciate any help!