# Questions tagged [physics-engine]

Software for simulating physics like collisions, forces, mass, joints, motion etc. Examples of physics engines are PhysX, Havok, Bullet and ODE.

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### Time complexity of solving constraints in physics engine

Erin Catto mentioned in a talk that solving constraints precisely requires cubic time and quadratic space. What algorithm is he talking about when he mentions cubic time? pdf of slides with following ...
75 views

### What is wrong with my gravity calculation?

Im trying to create a method to calculate the fall time for an object using real formulas. Well I came up with this: ...
36 views

### Real-time 3D Scene-reconstruction into Physics Engine

I am trying to create a game where the user scans the room using RGBD camera and reconstructs 3D scene. This scene would be integrated into physics engine, after an object recognition algorithm tells ...
196 views

### AABB Collision Detection Confusion

I am trying to understand and implement AABB collision to learn simple 2D game physics. I'm following a tutorial and its method is a bit different to other websites. It uses the center of the object ...
64 views

### how can I visually compensate for latency in a diep.io style game

implementing extrapolation using linear velocity, orientation and position like on here gafferongames.com/post/state_synchronization/ I'm a little confused if I want to extrapolate from a known ...
649 views

### Can I use the 2d physics engine in a 3d game (or viceversa) in Unity?

This is entirely for performance. The 2D physics are less expensive, but I require 3D for some scenes. I never need both at the same time. I know you can have 2D with an orthographic perspective in a ...
162 views

### Simulating circular motion with gravitational forces in Unity2D

I am currently messing around with a game where you control a black hole and use its gravity to fling planets at targets. I have the gravity calculations working pretty well when the planets start out ...
59 views

### Objects aren't rotating in sync

This is a follow-up question to How to reapply force applied to one object to another object I want to make two objects move, react to collisions and other stuff as if they were one. For example, ...
142 views

### How do I prevent falling tiles from bouncing on each other in my match 3 game?

I am working on a match 3 game in Unity. The tiles have a RigidBody2D in dynamic mode and a BoxCollider2D. When a match occurs ...
67 views

### How to reapply force applied to one object to another object

Edit: While I wasn't able to make the code work completely, I believe my question has been sufficiently answered. I want to make two objects move, react to collisions and other stuff as if they were ...
86 views

### Faster convergence in a physics engine

I've got my hands on the first edition of the book Game Physics Engine Development: How to Build a Robust Commercial-Grade Physics Engine for your Game by Ian Millington. Because I didn't really know ...
558 views

### How to handle player input with fixed rate variable fps time step?

I've made a system which uses the ideas from "Fix your Time Step" in order update physics. I'm having trouble finding standard methods for dealing with this when user input affects player movement ...
505 views

### Terrain collision with sphere and OBB

I'm implementing my physics engine for my 3D game. So far I've been able to implement collision detection between OBB, spheres and planes. The engine generate contacts and resolve them with an ...
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### Dividing properties between RigidBody and Collider

I am currently making a physics engine in Rust. The 2 main data structures concerning collision detection are: RigidBody: Physics-related aspects of the body. Contains a reference to a Collider ...
833 views

### Understanding constant acceleration in terms of game physics simulation

There are various integration methods that can be used for games. I am trying to write a simple physics engine deciding between semi-implicit Euler and Verlet variants. What I don't understand is ...
2k views

### Calculating impulse with multiple collision points

In my amateur 2D rigid body physics engine for a game I react on collisions between two bodies with an impulse j (formula 11) as explained here. To calculate this impulse I need one contact point P ...
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### Box2D physics are different on server and client

I'm using C# Box2D library for my server and client, they have similar world.step(), iterations and update function. At the same time they have different physics' results, difference is not fixed, it ...
3k views

### How to build a bones animation engine?

I want to develop a flash game. It would draw a stick man, and edit his pose. I think what I need to learn are bones animation and physics engine. Can anyone introduce some good resources to learn ...
146 views

### How do force fields scale?

Setting I am designing a 2d game in which a $1/r^2$ force acts between moving charged particles, and the number $n$ of particles is very large. To calculate the force between all pairs of ...
998 views

### Physics engine and squishing of stacked objects

I have a general question that seems to apply to most physics Engines (Box2D, Unity, Matter.js, …). I'm trying to make a tower of rectangular objects that are stacked on the [static/mass=infinity] ...
1k views

### Physic engine for snooker/billard game [duplicate]

Possible Duplicate: Is there an algorithm for a pool game? I think most billard/snooker games have a lot of problems with their physic engines. They are far away from realistic and you can't ...
245 views

### Unity like RigidBody physics in PyGame

I am trying to make game but first I want to make simple simulator. The goal is to have a ball fall onto a surface and then roll off the edge. Here is my code: ...
10k views

### How to achieve highly accurate car physics such as Liveforspeed?

Liveforspeed is a racing simulator, there is amazing amount of realistic physics. for example, tires get warm, tire actually deforms when you turn corners. You need to play this game with a mouse at ...
1k views

### What is inertia in a physics engine?

Inertia seems to be useful in a physics engine, so useful that even in Box2DLite, a demo of Box2D it hasn't been omitted. See this Body class from Box2DLite: ...
987 views

### Unity Physics Simulation - Limitations / Inaccuracies? Bounciness of a ball (pool/snooker balls etc)

I am playing with Unity physics engine. I have a pool table and a cue ball. Both have Physic Materials. If I start the game, with the ball floating about 1m above the table, it falls and bounces (...
52 views

### How to make a motorcycle running on a vertical circular track(loop-da-loop) without falling down due to gravity?

I am currently developing a game, motorcycle type game. Of course, my map is not just made up of simple line or curve. For example: a vertical circular track in the map. i've seen most 2D motorcycle ...
368 views

### Wall collision response results in jittery physics

I have the following game loop : ...
374 views

### Choosing the correct normal for a collision

I have taken the task of building a basic impulse physics engine. Circle vs Circle collision resolution has been done and I moved onto Line vs Circle. I can detect a collision and know that the normal ...
843 views

### Physics - How to calculate the next position of a ball rolling against a slope?

For a small C/C++ game project, I want to add some physics on a ball, to allow it to roll against the slopes of a 3d world, in the same way as the example visible in the image below: However I have ...
862 views

### How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based ...
29 views

### Deformable meshes based on torsional spring

I am trying to learn physics-based animation thanks to the book "Foundation of Physically-Based Modelling and Animation". They introduce the mass-spring model for deformable meshes. Although making ...
100 views

### Transfering an inertia tensor from local coordinates to another one

If we have an inertia tensor in local coordinates with a basis matrix B and we want to transform it to other local coordinates with basis matrix A, is it right to do the following: A* inv(B) *Inertia ...
893 views

### Unity Bowling ball physics

I am working on Bowling Ball game for android. And I want the Bowling Ball to feel like a Bowling ball in the real world. I've already tweaked the Rigidbody values and PhysicsMaterial but it's giving ...
71 views

### How do I determine the slope of a curve?

I am making a 2D game where the character rides on the curve of a graph. I need to find out whether the player is going uphill or downhill and calculate speed accordingly. The problem is that I am ...
1k views

### AndEngine Physics: Shape rotating but not updating physics effects

I was looking at PhysicsExample from AndEngine's Examples. I made the following change that I added a vertical line shape and created a fixture for it. Then I registered a rotation modifier for that ...
511 views

### physics engine without time steps

I'm looking for physics engines that doesn't use time steps. I don't think time steps are reliable, and I don't like how without tweaking the engine a bullet going too fast can pass through a wall ...
84 views

### How can I resolve collisions a little better?

I'm currently developing a physics engine and I'm not sure the best way to go about resolving my problem. I have a little box, that I can move around with in my scene. When I'm resolving collisions, ...
76 views

### Applying friction force not working correctly

I have a simple physics simulation I'm creating whilst following the Nature of Code tutorials on YouTube by Daniel Shiffman, at the moment I've just started learning about friction and have had a go ...
1k views

### Integrating Unity physics with Entitas

I've used Entitas a bit and it appeared to me as a great way of creating clean, modular code. I've seen few examples of games created with this framework, and most of them were puzzles, TD's, simple ...
61 views

### Modern way of getting points within a distance?

I'm making a game engine, and some components may want to interact with others based on distance. Currently, the component registers an update listener which runs on a loop, then it checks the ...
39 views

### Gauge vibration

Hello guys Im programming a gauge animation where there is a needle that points to certain values lets say each value equals to the amount of degrees the needle has to rotate to reach said value ...
884 views

### Why not derive velocity from position updates in games?

Is there a reason why retrieving velocity of a 3d object in a game engine vs deriving it from position updates is preferable? I am currently polling position at every step and deriving current ...