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gizmo99
Member
Hello,
I am writing a game where in Single Player mode, I need to move an object to simulate the computer's movement.
I have tried to move the Sprite directly but that loses the connectivity to the world (ie: it doesn't collide with anything in the world once I directly move the Object).
What is the best way to implement my Artificial Intelligence Logic? Is it in the Tick() method and by accessing the object's MouseJoint (I tried this but it crashes on Launch).
THank you all
gizmo99
Member
Thanks MobileBros and Jyoung for Answering my question...
I am totally confused on whether to move it in COS2d (then updating Box2d coordinates) or Move it in BOX2d directly.
When I update my coordinates in cos2d using sprite.location , it just jumps to the location and does not provide that natural movement towards it.
Is mouseJoint (creating it on the fly and destroying it afterwards) the only way ?
I assume you mean sprite.position, have you tried using cocos2d actions? Of course this would involve overriding sprite's setPosition method and syncing up the Box2d shape's position.
Adding to mobilebros suggestion, I've created a CCSprite subclass (PSprite - for physics sprite) that overrides setPosition, setRotation, etc. to ease the task. So I just call the normal methods and it takes care of the box2d body as well as the cocos2d sprite (though that gets taken care of in the world Step). I needed it that way due to the fact that I allow the player to move an object even when the world is in 'pause' (world->Step not getting called). This way I can move/reset object positions without any issues.
gizmo99
Member
Thanks for everyone reply...
I think I have to use the SetTransform Method on a b2Body. When the body is on one end of the screen and SetTransform is called, it just teleports to that location. How do I get the b2Body to smoothly move into place. Or is this not possible with SetTransform ?
Questor
Member
gizmo99,
To move a body slowly toward a destination you either have to do it manually (point for point) using setTransform or use ApplyForce (which applies a force over time) or ApplyImpulse (which applies a force immediately - or actually over an instant to be more precise).
The tradeoff here is that setTransform lets you move it precisely where you want but it will teleport it there, while ApplyForce and ApplyImpulse will move it smoothly toward the destination but you have to figure out how much force you will need to get the object to land where you want it (taking into account that other forces, such as gravity, will slow it down and affect it's linear and angular velocities.
The whole point of a physics engine is to emulate a real physical simulation, so there is not much you can really do besides work with it, or work *completely* outside of it (with setTransform). Cocos2d is better equipped in this regard as it allows you to all kinds of MoveTo, JumpTo, etc operations...but that is a whole different direction to go as it is not a physics engine, but rather a game engine.
Hope this helps clarify it a bit.
Regards,
Q
gizmo99
Member
Questor: Thank you for your succinct explanation. It helps a lot as I am new to Box2d and CoCos2d
I would like to keep the manipulation inside the Physics world ... instead of ApplyForce and ApplyImpulse.
I have been trying to move an object using its mouse Joint
//code Sample (I am testing to see if I can move the "computer" object along the same X axis as my "ball", Y position stays the same)
b2Vec2 b2Position = b2Vec2(ball.position.x/PTM_RATIO,computer.position.y/PTM_RATIO);
b2MouseJointDef md1;
md1.bodyA = _groundBody;
md1.bodyB = computerb2Body;
md1.target = b2Position;
md1.collideConnected = true;
md1.maxForce = 1000.0 * computerb2Body->GetMass();
_mouseJoint = (b2MouseJoint *)_world->CreateJoint(&md1);
computerb2Body->SetAwake(true);
_world->DestroyJoint(_mouseJoint);
_mouseJoint = NULL;
I do all of this in my Tick Method.
When I used the SetTransform method on the same b2Position Vector, it works. When I switched to the MouseJoint method, nothing happens. The same mouseJoint code is used else where to process TouchEvents and it works. But using it in my tick() doesn't do anything.
What am I doing wrong here :( ?
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