# Tagged Questions

Relating to the motion of objects through space (in 2 dimensions (x,y)) and time. Including concepts such as acceleration (thrust and gravity), mass, collision response, friction and more.

161 views

### Determining a sensible gear-like hierarchy for a series of connected objects

I would like a series of objects to behave in similar manner to a series of connected gears. This means that each black object in the diagram below will rotate at a speed based on the ratio of their ...
248 views

### Sprite Kit - containsPoint for SKPhysicsBody?

I have a ball bouncing around the screen. I can pick it up and drag it onto a "bucket". When my touches finish, I use the containsPoint function to check and see if I have dropped the ball onto the ...
122 views

### Moving one object from one point to another with acceleration

How would someone implement moving an object from one point in 2D space to another using these formulae to update objects: m_position.setX/Y( m_position.X/Y() + m_velocity.X/Y() * dt + 0.5 * m_acc * ...
554 views

### Use both AddForceAtPoint and change velocity property?

I'm using Rigidbody2D for some game objects. It seems that when I AddForce() or AddForceAtPoint(), the game objects are mostly affected on the Y axis and hardly at all on the x axis. I don't ...
202 views

### How to impale and stack targets correctly according to the collider and its coordinate?

I'm making another simple game, a catch game, where a spawning target game object must be captured using a skewer to impale it. Here how: At the start, the falling object (in red) will fall in a ...
16 views

### How to move sprite mimicking mouse/touch position on some part of the screen?

I am having a difficulty and I am been doing it wrong, I think. I want to move sprite relatively to touch. Just like when you are playing space shooter like 1943. I just learning some math and try to ...
84 views

### How do I make circles bounce off each other realistically?

I'm trying to create bouncing balls with realistic physics. At the moment, when the balls hit each other, they bounce back in the same direction they came from. How do I make them more realistic? I ...
175 views

### Cocos2dx+Chipmunk: Fully elastic collision between moving bodies

I'm using Cocos2dx and the built in Chipmunk physics engine, and currently I've got my PhysicsBodys' materials set up with: Density=0 Restitution=1 Friction=0 in order to get fully elastic ...
749 views

### Spritekit - gradually apply force vector in different direction (space ship turning)

I have a space ship that I'm applying a force vector to using a joystick for control. I would like this to smoothly fly around when I'm switching directions.. Exactly like minisquadron if you've ...
21 views

### Bouncing projectile off of sprite, the sides work but top and bottom do not

I'm having a problem bouncing a projectile off a sprite, we've been asked to move the projectile using the equations of motions which makes things a little more difficult but as far as I can see what ...
81 views

### Good collision resolving mechanism

In my game i have plenty of objects that can collide. Literally, most of them can collide with each other.The problem I'm facing is that i can't come up with some good collision resolving way. How can ...
315 views

### LibGDX Bounding Rectangles

I'm creating some rectangles surrounding my sprites for my player and bullet class to detect collisions with the overlaps method in Intersector class of LibGDX. I have a question: When I instantiate ...
478 views

### Swinging a sword in Xcode with Sprite Kit

I'm working on making an RPG in Xcode, and I'm having a major gameplay issue when it comes to having my character swing his sword in a way that is realistic and gameplay compatible. Right now, when ...
58 views

### Relative movement in Box2D (keep object from falling off planet)

I'm creating a game with planets orbiting around a sun, like this: The brown square is the earth, rotating around its center and around the sun. The yellow square is the sun, which doesn't move. Now ...
108 views

### 2D bouncing formula doesn't work properly

am new to unity, and i am trying to create a bouncing ball, so i've did many researches about bouncing realted physics and i found a formula : Formula: -2*(V dot N)*N + V Where V is the velocity ...
496 views

### Trajectory Projectile with Collision Detection

Right now I am trying to create projectile for cannon in which I want to detect collision also. At present I have simple working projectile after using two references Unity – How to display ...
419 views

### How is destructable terrain made in SDL?

I'm looking for terrain that gets removed in chunks (like in Worms, of instance). How do you do this in SDL?
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### Sizing a Box2D ground object

I am developing a platformer game using SDL2 for graphics and Box2D for physics. I am currently designing my levels and would like to know if it is better to make the static part of each level (ie: ...
15 views

### Need help in getting sequential impulse method working

i have made a very very simple physics system based on sequential impulse method - with single contacts only and no angular rotation at all. Contact points are calculated using separating axis ...
86 views

### Create a 2D orbit trajectory like in angry birds space and a circular orbit

I am working on a 2D game, and I am working on adding some space physics : I need to find a way to create a circular orbit and an orbit like angry birds space ( the spiral trajectory ) . So there is 2 ...
59 views

### Farseer: Friend/Foe Collision - cannot push foes but friends

we are using Farseer in our project and I try to find a setup to achieve the following quite complicated collision behavior: Friendly Units can push each other aside. However, the push should be a ...
111 views

### How to render multiple objects as a single object for fluid simulation?

I'm trying to do fluid simulation using particles in 2d game. I have larger particles, which interactive each other physically, those particles collide with environment (e.g wall,obstacles) to ...
843 views

### Ease Rotate RigidBody2D toward arbitrary angle

I'm trying to make a rigidbody2D circle return to an orientation after a collision. But there is a weird behavior I do not expect - it always orients to the same direction. This is what I call in ...
114 views

### Storing rigid body collision shapes in local or world coordinates

I'm writing the beginnings of a lightweight 2d rigid body engine (in javascript, as a hobby project), and i'm debating whether to store collision shapes in local or in (updated as needed) world ...
547 views

### Cocos2d and Body with few collision shapes using chipmunk

I'm using Cocos2d (0.99.5) with chipmunk physics engine. Currently I'm trying to place a body into space which is combined from few circle shapes. Let's say I have a corresponding sprite image with ...
26 views

### LibGDX make an object rotate around something

I need to rotate and object, which should be a circle made up with a ShaderRender, around a specified point. In LibGDX there is a method or something which allow me to do this? If it doesn't exist how ...
14 views

### how to trigger a ball from rotating cube in z axis

how to release ball from the cube which is rotating in z axis, ball should move in Y axis and ball should be reloaded after releasing the ball ?? Thanks in advance cheers Gokul
32 views

### wheeled 2D character controller platform edges problem

I have built a little wheeled 2D character controller (a rectangle for the body and a circle for the legs with a motor joint). Everything is ok but the problem is that when the player reaches the edge ...
65 views

### Rain World : How to have intelligent movement / animation?

In the project RainWorld the characters seem to move "intelligently" as they move "unrestricted". They seem to know "how" to move their limbs and "what" needs to be done. Here for an example the ...
15 views

### How can I track a leader vehicle at a specific angle and distance?

I am using Matlab and have code which allows a vehicle to find its way to certain coordinates chosen by the user. I now want to add a second vehicle which stays fixed at a specific distance and angle ...
97 views

### Physics2D.OverlapCircleAll seems to be bigger than my radius

Im trying to make a "Scorched earth"-like game using unity. I managed to fire my bullet and make it explode on contact. What I am trying to do is do some damage to the tanks even if the bullet didn't ...
53 views

### Does unused 2D colliders in Unity affects performance? Is an Edge Collider more performance friendly than BoxCollider2D?

I am using a lot of gameobjects for my platformer that uses BoxCollider2D component to make the scene floor. But only an a selected set of gameobjects actually have some interaction with the player, ...
37 views

### PhysicsJS object falls through the world

I have a problem while using PhysicsJS when it comes to collisions. I created a physics world, an object and applied gravity. I put the object at a certain position, it falls down because of the ...
128 views

### SpriteKit: Is applyImpulse not working correctly?

I am writing a free throwing system and because of this, I created a ball using following code. self.ball.position = CGPointMake(posX, posY) self.ball.fillColor = SKColor.blueColor() ...
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### How to tell if the ball is on the floor (in nape)?

What I wish to do in pseudo code: points = Get the set of all points (x, y) where the ball is touching other surfaces. point = Get the point out of that set with the minimal (y) value. Check if that ...
19 views

### Box2d - body size or spatial distribution matters for better simulation?

Box2D better works for limited sizes: Box2D works with floating point numbers and tolerances have to be used to make Box2D perform well. These tolerances have been tuned to work well with ...
51 views

### Calculation technique for 2D inertia tensors?

Just wondering what the techniques are out there. It's only 2D so I figured there'd be a good chance for there to be a "one size fits all" solution out there that's essentially an analytical solution. ...
116 views

### 2D Distance Field as collision handler method

Pixeljunk Shooter has really cool fluid simulation. I found the dev's video explaining what they did. Here I understand that it is particle based simulation Smoothed Particle Hydrodynamic I can ...
90 views

### Breakout Clone: Ball isn't bouncing as expected

So I'm working on a Breakout Clone using Unity 2D Physics only, and I'm having some trouble with the bouncing effect. Every object in my Scene has a Bounciness of 1. First, this is the code of my ...
62 views

### How to determine positions to draw lines on a screen with AndEngine

I have a screen (480x800), M(mx, my) is a static point, and N(nx,ny) is a dynamic point on screen. Position of N(nx, ny) depends position of touch. I want to determine position of P(?,?) and Q(?,?) to ...
161 views

### Box2D collision damage calculation from postSolve or not?

I'm using postSolve to get impulse then calculate damage base on that impulse. But there's some issue: Stability The damage isn't stable. When the same ball is hitting with same speed, the damage ...
82 views

### Particle friction with variable timestep in XNA

Alright, so I'm working on an engine of sorts in XNA (yes, it's deprecated, I know) and I'm implementing my own particle system. I've defined a "ParticleEffect" such that when it's supplied a GameTime ...