Adding a second fixture as sensor to body in Box2Dweb

Question

I have two problems adding a sensor fixture in the following code. The repositioning vector b2Vec2(0,50) is not working; the second fixture is still centered at the origin of the body. Both fixtures can be seen in debug mode but I can't move the sensor fixture to the foot of the main fixture.

Secondly, when isSensor is true I am not receiving any PostSolve events. When it is set to false I get the appropriate events (along with collision). How do I make this a sensor that will not collide with other bodies but still raise events. Thank you for your help.

    // FIXTURE DEF
    var fixDef = new box2d.b2FixtureDef();
    fixDef.shape = new box2d.b2PolygonShape;
    fixDef.shape.SetAsBox((25 / 2 / SCALE), (46 / 2 / SCALE));
    fixDef.density = 0.99;
    fixDef.friction = 0.39;
    fixDef.restitution = 0.0;
    fixDef.userData = "SBody";
    fixDef.filter.categoryBits = CAT.SOLDIER;
    fixDef.filter.maskBits = CAT.GROUND;
    this.view.body.CreateFixture(fixDef);


    // ADD FOOT SENSOR
    fixDef.density = 0.1;
    fixDef.friction = 1.;
    fixDef.restitution = 0.1;
    fixDef.userData = "Foot";
    fixDef.shape.SetAsBox((10 / 2 / SCALE), (100 / 2 / SCALE), new box2d.b2Vec2(0,50), 0);
    fixDef.isSensor = true;
    fixDef.filter.categoryBits = CAT.SOLDIER_FOOT_SENSOR;
    fixDef.filter.maskBits = CAT.SHIP | CAT.GROUND;
    this.view.body.CreateFixture(fixDef);

score 1 · Accepted Answer · edited May 23 '17 at 12:13

I was using the tip in this answer https://stackoverflow.com/a/4707127/1172891 that said to add positioning as the 3rd parameter, but I recently found that SetAsBox cannot take a 3rd argument, maybe it used to. Instead I found SetAsOrientedBox is a similar method and accepts the 3rd parameter for positioning. Found on the Box2dFlash reference http://www.box2dflash.org/docs/2.1a/reference/Box2D/Collision/Shapes/b2PolygonShape.html

For the sensor callbacks, I was only trying the PostSolve at first. I recently thought to try the other events like EndContact and found that it worked. I then found this page that seems to be the only place that explicitly states that sensors only raise BeginContact and EndContact events: http://www.box2dflash.org/docs/2.1a/updating in the Events section.

Hope that saves someone some time!

Adding a second fixture as sensor to body in Box2Dweb

1 Answers1