I have a simple project built with Cocos2D and Chipmunk. So far it's just a Ball (body, shape & sprite) bouncing on the Ground (a static line segment at the bottom of the screen).
I implemented the ccTouchesBegan/Moved/Ended methods to drag the ball around.
I've tried both:
cpBodySlew(ballBody, touchPoint, 1.0/60.0f);
and
ballBody->p = cgPointMake(touchPoint.x,touchPoint.y);
and while the Ball does follow my dragging, it's still being affected by gravity and it tries to go down (which causes velocity problems and others).
Does anyone know of the preferred way to Drag an active Body while the physics simulation is going on?
Do I need somehow to stop the simulation and turn it back on afterwards?
Thanks!
Temporarily remove the body from the space.
If you want the object to have inertia when you release it, that's a different story. The cleanest way is to attach a fairly stiff spring between the ball and a temporary sensor body that moves under the control of your finger. When you let go with your finger, the ball will retain whatever kinematics it had while you were dragging it. Be sure not to remove the ball from the space in this case.
You aren't updating the velocity of the object when you aren't using cpBodySlew(). That is why it falls straight down.
A better way to do it is to use a force clamped pivot joint like the official demos do to implement mouse control. http://code.google.com/p/chipmunk-physics/source/browse/trunk/Demo/ChipmunkDemo.c#296
Related
I am trying to make a Retro Tenis Game in Unity2D but I have some issues with the colliding system.
My controller does not collide with the walls. It goes through them.
It should stop in the wall like pic1 but it goes through it like pic2.
Can anyone help me, please?
pic1
pic2
UPDATE#1: I added a RigidBody component but it does not fix it. (pic3)
pic3
You shouldn't use the colliding system for this purpose. It would be much better that the script in charge of moving your paddle was able to control its maximum and minimum height too (note that the screen size can change, and the paddles should move at different heights depending on the screen size).
Although if you want to do it with the collision system and "walls" that limit the space of the paddles, both the "walls" and the paddles need to have a correctly positioned BoxCollider2D and the paddles an extra kinematic Rigidbody2D too (as they can move).
Also make sure to move the paddles using physics and not modifying its position with transform.position (see Rigidbody2D.MovePosition)
Edit: Unity2D physics system is rather a complicated topic and difficult to get it well on your own. I'd suggest to learn the basics in the Unity Learning Platform. You could start with this project.
You need add RigidBody2D to your "circle"
I would like to move a tile with drag and drop in Unity 2D. The tile is a sprite. The scene is an 'Unblock me' or 'Blocked in' like gameplay.
Because the tiles in real life correspond to physical objects it seemed be to a good idea to model them with colliders and rigidbody. The border of the table surrunded with invisible colliders. I hoped these will constrain the moves of the tiles realistic, when the player moves them.
Then I implemented a simple (mouse based) drag and drop behavior which is worked perfectly except the moved tile penetrates to other tiles and the border, and sometimes jumps over them. Then I learned if I am overriding physics by explicitly setting transforms position (which I do exactly in my drag and drop implementation), this will happen. OK I accept, I should set only forces, ect. on rigidbody never directly the position.
Now the question:
I am stuck here. I still want to drag and drop like user experience, and some realistic visual result. When in the real life a player moves a tile, it seems it is "glued" to its finger. How can I achieve this (ot at least similar) with just applying forces? Any suggestions or point similar existing sample/blog code?
(I know as a backup plan I can omit all the physics and constrain the tile positions by code, and create some tweens to move the tiles. Is the real solution (what I am asking for) so complicated I should vote on this backup plan?)
Edit
According to comments I've added a video:
There is nothing wrong with the way you are manipulating your dragging. The beauty of developing is being able to do things in your own way. If it works for your game, then don't fret.
Now, i recommend:
Create a new physic material. Assets > Create > Physic Material
Set your new physic material inspector settings both to 0
Attach the physic material to all your wall object colliders. This should allow for your object being dragged to move smoothly against the walls without chopping.
Do a check to see if your mouse is over another collider. If so, then stop the movement in that direction.
Since your movements seem to always be on a single axis, on collision, tell your object to snap to the edge of the wall object. You know the Wall position and scales, also you have the position and scales of the object being dragged. with that you can write a function that will offset it to the correct position when the collision occurs.
Let me know if any of that works out :P
I'm new to Unity and the is working on a personal project. In the following picture, you can see a blue plane in the middle, I want to use it as a ice plane and there should be no friction when user is walking on it. In another way, if I press 'w', the object should move forward until it hits an object. I know there's a built-in function called physic material, but it works only when the plane is tilt at some angle so that the object will slide down from the top to the bottom, but if the plane is placed in a horizontal level it will not work. Anybody has any suggestions for it, thanks.
Answering from my phone and off the top of my head, but look at using input.getaxisraw() to get your direction data then add forces. use triggers to stop the movement when you reach a trigger on another object. There were some good tutorials on Collisions and triggers on unity tutorials. To elaborate more, you can add colliders to the objects that you want your player object to interact with physically. So for your player object you can add code like:
OnTriggerEnter(collider c) {
// stop movement
}
I am working on a tabletop game that user controls using accelerometer in the phone. It is pretty similar to Labyrinth on iOS.
The scene contains a tabletop created using planes and cubes, and a sphere as a ball. As it works in Labyrinth game, on tilting phone ball should drop to the tilted side, while the camera stays centered to table. I am trying to do similar thing where user tilts the phone, and objects on table move to tilted side.
Currently, I add the x and z component to Physics.gravity on tilt. Sadly, this change in gravity does not affect the ball which stays put on the table. Use gravity is selected for the ball, and it drop down from height to the tabletop initially and then comes to halt. After the initial drop, ball does not react to any gravity change.
I have also tried rotating the whole table, but using transform.rotate does not work either. The table rotates perfectly, alongwith the camera, but the ball stays put hanging in the air. So, currently I am out of my depth about the issue.
Is there any other way to allow tilt action registered, so that ball moves to the tilted direction? I cannot use addforce function, as there are multiple objects which need to react to tilt, and it will be difficult to keep track of that many addforce calls. How else can I get it working?
See this post for some related information.
As for why your sphere is sticking to the table, can I assume your sphere has a rigidbody? If so, you need need to wake it up:
if (rigidbody.IsSleeping())rigidbody.WakeUp();
Ideally you would make that call only after detecting a change in orientation/gravity, not every frame.
I made a game that using a character that can moving left or right by touching the screen, above the character, it is a apple, what i need is the apple will fall down, the character may push the apple up again just like playing volleyball.
That's the problem,what i have learnt from "bounding ball" is give a sprite a shape and body, then they would collide automatically,when i give shape and body to the character, the animation is not work, the character moved and after a second he "jumps" to the starting point,whatever i using setPosition or Action(MoveTo) to sprite are also useless
moving the body is not work too.I use touchmoved to set the body->p,it keeps shaking and when i release the button, it "fly" alway out of bound..........
Can anyone tell me what should i do or give a similar example(e.g. volleyball and something like that),Plx help!!!
I appreciate that if anyone can give me a hand.
Adding a chipmunk body and shape to a sprite is not the best way to go about this. Try not to think from the screen's point of view! Instead, create a controller that contains a reference to the physics body and the sprite.
Using a physics engine, such as chipmunk, can be a bit daunting. It helps to enable debug drawing. Have a look into how you can best do that! There is some code you can take from the cocos2d chipmunk example, that comes with the normal cocos2d download)
I take it you've added a "ground" shape as a static shape and have gravity set?
When you move a body with body->p = cpv(x,y); the problem is that you don't change the objects state other than it's position. To the physics engine, it's like you teleport the object. If the object was falling, it will still be falling.
So now, your falling object is not touching the ground. Its speed increases. You "teleport" it again.. but until it bumps into anything, gravity will keep increasing its falling speed.
So, if you move an object to another point, be sure to reset all forces and the velocity on that object, if this need to be done!
A better way than using body->p is to use these functions:
void cpBodySlew(cpBody *body, cpVect pos, cpFloat dt)
void cpBodyUpdateVelocity(cpBody *body, cpVect gravity, cpFloat damping, cpFloat dt)
void cpBodyUpdatePosition(cpBody *body, cpFloat dt)
The documentation of these functions isn't too ridged, but there's other documentation out there. Give it a google :-p I haven't fully mastered using these functions yet either (I'm still trying to get around Chipmunk too) but they're the way to go about it.
Alternatively you can (instead of setting body->p) set the velocity of the object directly (though cpBodySlew does this for you)
The latest chipmunk code is doing this with a pivot joint in between the object to be grabbed and the mouse (touch): ChipmunkDemo.c.
See also: Mouse interaction