# Tagged Questions

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

69 views

### Controlling the movement of player by sprite using Mouse

I want to move the player by pressing down on the mouse and moving around by dragging. The player won't move to the position of the mouse. Instead it should be relative to the players current position....
39 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 ...
267 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 ...
54 views

### 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: ...
305 views

### Simulating beer pong physics in Unity

I'm trying to create a simple beer pong game in Unity. The basic idea is this - when it's your turn to shoot, you use your mouse to pick a point on the table that you want the ball to hit and bounce ...
59 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 theorem....
102 views

### Colliding of 2 moving objects

I am making 2d Game with my own Physics (without using of Rigidbody - some kind of challenge for me). I have two objects which are moving, and their velocity vectors. I have some unmoving objects. ...
74 views

### How to prevent bullets from passing right through entities?

(sorry for bad english) I'm making 2D arcade game. I write all of physics stuff myself. The problem involves bullet behaviour. Imagine bullet flying towards some entity. If the bullet's velocity is ...
329 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 ...
701 views

### How can I simulate the gravity of a sphere instead of a plane?

How can I simulate the gravity of a sphere instead of a plane? For a naval warfare game, I wish to implement a surface that simulates a curved plane with horizon. The plane is rendered with water ...
58 views

### Libgdx bouncy effect in a wall

I have an element inside the screen and I want to set my phone's bounds as a wall where elements are bouncing. I want it to be physically correct. How to do this?
258 views

### Sphere to plane collision never rearching resting contact

I have been trying to have a sphere to plane eventually lead to the sphere coming to a resting contact, but my sphere will end up always bouncing forever. It will bounce correctly for the first few ...
234 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 ...
225 views

### How do I calculate rotational impulses in rigid body collisions?

I'm writing a simple 2D physics engine to help me understand the inner workings of physics engines. I'm following Randy Gaul's tutorial which can be found here and It's been extremely useful and ...
161 views

### Calculating density of an object

I'm using Box2D for physics in my game, and one of the things it needs to know when creating a shape for a physics body is the shape's density. I had no idea what value I should specify, so I went to ...
502 views

### Unity - Joint tearing under larger force

I have a chain that is made of connected configurable joints. I used ultimate rope builder for the rope chain creating. The problem is that when i apply a larger force to the chain, it starts to tear ...
2k views

### Unity Rigidbody gets pushed through collider by another rigidbody?

I'm setting up the interior of a house in a 2D platformer. Inside the house is an NPC with a box collider and rigidbody attached, and the house is boxed in by four edge colliders. My character also ...
396 views

### Sprite Kit - keeping character level with the terrain 2d endless runner

I've been trying to figure this out exhaustively for the past few days and still haven't found an answer. I have an endless runner built using swift where the character is fixed and the terrain moves ...
201 views

### Determine if an object is inside a ship's turn radius, rotation via torque

I have a 3d space game where all ships move around using physics. I am trying to determine if a given object is reachable by a ship at a given velocity and turn radius. I believe the formula for turn ...
87 views

### unity3d - Object keeps falling down

I have an object that moves towards another object using this line : transform.position = Vector3.MoveTowards(transform.position, target.transform.position, speed * Time.deltaTime); this is it's ...
256 views

### Physics: calculating angular acceleration in world vs local space

I have a pretty simple rigid body simulation written in Python. In my code I calculate the angular acceleration using formula: angAcc = torque * inertiaTensor^-1 (note row-major matrix order) Now, ...
230 views

### Collision between a sphere and a mesh(height-map)

I am trying to implement a method that detects the collision between a sphere and a mesh and reflects the vector of speed. I have a method, that detects a collision between a sphere and a triangle and ...
247 views

### Calculate Orbit Path/Ellipse given mass, velocity, and distance (2body)

Calculate and draw the path of an orbit in a 2 body problem given the mass, current velocity, and distance of both bodies? We're working in Unity and will be using the default rigidbody.mass to start ...
1k views

### How is RTS Local Avoidance Done?

Currently, I'm simulating physics impact forces for local avoidance of units but this method sometimes pushes units out of formation and has very undesirable effects when units clump up. For RTS ...
86 views

### b2DistanceJoint with frequency equal to 0 vs b2WeldJoint

What is the difference of b2WeldJoint and b2DistanceJoint? They both have frequency and also when you put frequency of Distance Joint to 0 it acts like Weld Joint. It seams that you can create ...
354 views

### Why does my character stop a little before landing on the ground?

I made a little game with side-scrolling and a box (the player) jumping across the level. The simple physics are almost done, but I have two problem with the way things behave: On landing, the box ...
212 views

### In Box2D, how do I create an infinitely oscillating spring?

How do I create an ideal spring that can oscillate indefinitely using Box2D? A b2DistanceJoint works almost perfectly, but it eventually slows to a stop, even with damping set to 0. I think it is ...
119 views

### (Fat) ray cast with MPR OR GJK?

I know that it's possible to see if a line segment or a swept shape (to make a "fat" line segment) intersects objects using MPR and GJK. Is it possible in those situations to find out the distance ...
63 views

### Are GPU physics implementations branchless?

I've implemented MPR on the CPU and in pixel shaders (long story!) and there seems to be unavoidable conditional loops both to find the starting portal as well as to find the final solution. I know ...
137 views

### Ball oblique impact physic in Java?

I know Q3 + Q4 = 90 I searched internet and many physic topics, but not found how to calculate this values in Java? (I found V3 and V4 but not found Q3 and Q4) So how can i calculate V3, V4, Q3, ...
97 views

### Unity 2D Current object force

I'm working on a game with an entity firing a shot. This shot could destroy other entities as well as the entity who generated the shot. My first step was to apply a force to the rigidbody2D of the ...
310 views

### Simulation of ball movement in a 3d landscape. The easiest way?

I have a landscape(generated via Perlin noise) and a ball. I want the ball to move along the geodesic(implementation of basic physics: gravitation, friction). I thought to do raycast around the ball ...
209 views

### Circle-Circle collision resolution

This seems easy but I can't figure it out, when I have one circle(c1) collide with another(c2) I give the c2 circle the heading of c1 and send the c1 circle on the normal vector to the heading (the ...
523 views

### What is wrong with my 2D orbit calculation?

I am working on a 2D game, and I am working on adding some space physics, so I need to find a way to create a circular orbit. I want to make my game object move on a circular way around a planet. I'm ...
159 views

### Speed needed to make a car jump from a ramp

I need to make a car jump from a ramp to another, and I need this to be done using AI so I thought it would be enough to set a fixed speed for my car when near the ramp, in order to let it jump ...
471 views

### (Unity) Physics based movement vs Straight position change

Unity provides a cool physics engine for game development and I want to utilize it in my game. Shorter version I want to use physics engine for everything else other than character movement because ...
136 views

### Twin-stick controls for a cohesive group of agents

I'm trying to implement a classic twin-stick controller for a group of physics-based game objects. Here are the rules I'm trying to follow: Agents always stay close to each other within a certain ...
172 views

### Correct way to integrate scaled axis angular velocity into a quaternion

Across my travels on the internet I have came across to ways of integrating a scaled axis angular velocity into a quaternion. The first way converts the angular velocity into an axis angle quaternion ...
353 views

### How to slow down a Sphere smoothly in a world controlled by force and stop it (Unity 5)?

I am a beginner and I started to use Unity 5. I play with tutorials on the site and documentation. I was basically testing springs, physics materials etc. I have a problem understanding probably a ...
19 views

### How do I find at least the closest penetrating point with SAT? [duplicate]

For more accurate simulations, I want to find the closest point of another polygon to one polygon's center when they collide. Is this possible with the SAT algorithm? Is it a good strategy at all for ...
77 views

### How do I calculate force from collision between 2 rigidbodies in 2D?

I have a physics engine based on the Game Physics Engine Development by Ian Millington. In chapter 7.1.1, it provides the formula: V = (pA.Velocity - pB.Velocity) * (pA - pB).normalized where V is ...
88 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 ...
211 views

### (LibGDX/JAVA) How can I get a rectangle to rotate with this pendulum so I can start detecting collisions?

One of the objects in my game is a pendulum that swings in a semi-circle. This is done by having an update() method like this: public void update() { angleAcceleration = +1.81 / length * Math.sin(...
414 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 * ...
151 views

### Calculate intersect point / aim point

I'm working on a simple game, and I need to calculate the position to aim. Since my math days are a bit behind me, I put together a simple example to illustrate: So given that I know the position ...
174 views

### Why doesn't this 2d physics calculation yield the desired jump height?

I found a formula for gravity and jumping in this article: http://error454.com/2013/10/23/platformer-physics-101-and-the-3-fundamental-equations-of-platformers/ I implemented this formula and ...
73 views

### unity2D Top-Dow Mobile rigibody2D

im using this code for my 2D TopDown mobile player movement.but when i move player With UI Image buttons player keep moving.it didnt stop.and also player starting of move he is very slow. the he ...
221 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 ...