# Questions tagged [physics]

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

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### Handling movement on sloped surfaces - clamping character to sloped surface

I've noticed that a lot of people seem to have this issue but I've yet to find an actual working solution - when a rigidbody-based character controller (I'm not using Unity's character controller) ...
2k views

### Lunar Lander calculating gravity, acceleration and collision in GameMaker

I've already asked this on the GameMaker forums but had no response so far. I'm making a little Lunar Lander game as my first foray in to GameMaker, I'm wanting to have the ship land and take off ...
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### How can I create a set of collision points for an arbitrary mesh?

In my project I am working on automatically deforming an arbitrary mesh with respect to another arbitrary mesh, within the context of user generated content, similar to this deformer being developed ...
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### 3D Physics Engine Collision Response: Solving Simultaneous Collisions via equation

I have been implementing a basic physics engine for a small game project I'm working on. It has very specific requirements, so I decided to try and write my own physics engine to meet them. I found ...
297 views

### Rotation of a ball moving on a surface

I have a ball that moves along a platform. The ball is characterized as a sphere that has a radius and a position. The platform basically is a rectangle consisting of two vertex triangles. Its class ...
227 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: ...
166 views

### How can I determine "exact moment" of collision with ray casting?

I'm currently brainstorming how the physics for my game engine is going to be handled. It's top down and I'm thinking of using ray casting for collision detection. I've reached two potential problems (...
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### Force propagation through physic bodies constraints (as non-penetration)

First, some context I'm currently implementing a (well, tiny) game engine using a predictive approach. The idea is to compute when a state change will occur, and only update state at time of the ...
1k views

### Friction due to gravity in an impulse based physics engine

In my physics engine, I'm using impulses to solve collisions. I'm basing all calculations on these equations: ...
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### Disc Golf Physics in Unity

I am trying to make a frisbee golf game, and I am stuck on the physics of the frisbee. I can get the disc to fly, but I have not been able to add spin or make it act the way a frisbee would in real ...
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### How do you compute for angular spring physics for physics joints in game engines?

I'm working on fixing Godot's physics joints. Currently, it uses Euler angles and it doesn't help me in building active ragdolls for my game. I heard that using quaternions is the way to go. So I ...
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### 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 ...
334 views

### With gravity enabled, how do you move a RigidBody forwards at a specific speed?

I have a perfectly smooth cube on top of a perfectly smooth plane. I am applying a forward-force of 1 unit per second, using ...
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### How to implement path-finding with a large number of blocking agents following similar paths?

I want to implement a demo like creeps laning in Dota 2. So for simplicity, there is Left team and Right team, they are enemies. Units from Left team move toward Right base, and units from Right team ...
315 views

### How to properly write "stick to surface" character logic that handles unexpected large time deltas?

I've been trying to wrap my head around this issue: in a 2D platformer game (but this may as well apply to 3D games) I want the character to "stick" to the surface that it's moving along and at the ...
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### Bullet Physics Scaling rotational part of 6DoF Spring Damper

I am currently trying to scale up my setup (consisting of two rigid bodies connected by a btGeneric6DofSpring2Constraint) to fall within the suggested dimensions for a concise simulation. In order to ...
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### Add Rigidbody and MeshCollider at runtime : is it a bad practice?

Good day. To simulate an explosion of a vheicle, I decided to do this: When I need to explode veichle , at runtime, i add rigidibody for every single part of veichle (5-10 part: door, wheel, hood ...
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### UNET Performance of (many) Kinematic Rigidbodies

I am building a game in Unity in C# using the UNET networking elements. I am trying to figure out what is the performance cost of kinematic rigidbodies? My understanding is that, when kinematic, ...
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### Solving constraints/joints in 1D

For n points moving in 1 dimension. Position and velocity are known for each point. Each frame a basic integration is done for each point: ...
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### How to aim with a spaceship in 3D considering its angular momentum?

So I have a spaceship and I have 6 degrees of freedom. At a given moment the following vectors are known of the spaceship: Local forward. Local up. Local sideways (may be implied from the previous ...
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### How to code a non-newtonian spaceship control script?

I'm working on a simple 3D space combat game, and I've decided to go with simplified physics over proper newtonian motion, similar to the space sim Oolite, and more 'arcade' style games. I basically ...
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### How to implement grapple hook and swing

I'm trying to make a retro style grapple hook / swing system that has a constant speed and is not based on real-life physics. Like the one in Axiom Verge, Bionic Commando (NES) and Super Metroid.
75 views

### Calculating spring constant c

Suppose we have 2 springs with different values for m and k. The first spring is given an arbitrary dampening value, ...
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### How to connect particles to rigid bodies in LiquidFun?

In vanilla Box2D various types of Joints can be used to connect two rigid bodies together. The LiquidFun extension brings the Particle Module, but I was unable to find a way to connect a particle/...
424 views

### How to accelerate car based off of Animation Curve?

I am making a karting game and I want the karts velocity to accelerate based off a curve. This would allow me to quickly iterate different types of cars that accelerate in different ways. I was ...
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### How do I get the consistent time it would take for two points to reach each other in circular motion?

I'm making a 2D game. It involves the player swinging around a grapple hook in perfect circular motion, however, I want to make the cooldown for this ability based on predicted end position for the ...
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### How can I make my table move more realistically after a collision?

Using Unity 2020. I have a character using CharacterController and Rigidbody, colliding into the end of a long table. My table has, as a root object, the mesh and the Rigidbody. It also has, as child ...
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### Interpolation on Rigidbody2D not working

I'm trying to achieve smooth movement for a ball. I seem to be failing to achieve this and now I've created a sample scene, which shows my setup from the game and the problem exists in that sample ...
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### How to achieve variable jump height in an elegant and natural way

I am making a platformer, with a methodical approach to player physics. This is how I do variable jump height: ...
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### Handling strange physics behaviour while sliding between coplanar surfaces

We've got a character setup based around manually resolving collisions, and we're using bullet to do so. Our characters have a kinematic rigidbody to push things around, but their movement and ...
840 views

### Realistic 2D air friction in unity

I want to make an evolution games similar to this old games that was generating cars. Except I want it to be more realistic. So I want air friction to impact the speed of my cars, but how do I do ...
815 views

### calculating the trajectory of an object in SpriteKit when an impulse is applied to it

I want to make a trajectory line of little balls of where the object is going to go after an impulse, sort of like what is in Angry Birds. I did some research and it seems that the physics in ...
574 views

### Simulating Water by changing Y values of Quad Vertices

hopefully this isn't too difficult to answer, but I'm stuck and could at least use some input. I'm working on simulating water for the first time with basic wave functionality. As in I click at a ...
564 views

### 2D platformer:How to avoid "bouncing descend" when walking down slopes?

I've been working on implementing slope collision by SAT(Separating Axis Theorem). And then I have a trouble. When my character walks down slope, it moves like a bouncing ball: The slope has 3 ...
109 views

### Soft-restart tampers with physics determinism, resulting in different results

Updated question I have a Spawner entity that spawns my Rollables: ...
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### Unity applying forces using animation

I'm trying to make a croquet mallet swing to hit the ball using an animation that rotates the mallet mesh. The mesh appears correctly positioned to hit the ball in the center but the ball doesn't go ...
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625 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 ...
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### 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 ...
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### 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 ...
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### How do I compute the angle between a pixel on an irregular curve and a circle colliding with it?

I'm building a custom physics engine to accompany a level-editor. This image shows how the level-editor outputs levels: Now, some explanation is in order. The curve is defined by the red points. ...
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### Newton Game Dynamics: Making an object not affect another object

I'm going to be using Newton in my networked action game with Mogre. There will be two "types" of physics object: global and local. Global objects will be kept in sync for everybody; these include ...
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### finding the angle to launch a projectile at a 3d coordinates

I have a game where the user can shoot a bullet and the bullet flies through 3 dimensional space and eventually hits the ground somewhere. My question is how can I calculate the ...
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1 vote
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### How can I constrain a RigidBody ball to move along a path, but only apply forces to keep the ball on the path without adding velocity?

I'm currently working on a game and I'm hung up on this particular issue. I have a ball that is a RigidBody. The RigidBody is ...
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1 vote
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### Applying impulses simultaneously at each contact point or sequentially?

I'm coding a 2d physics engine in python, and I'm struggling to understand the right way to implement collision resolution when there are multiple contact points. Consider a very simple collision case ...
1 vote
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### How can I simulate locking or limited-slip differentials in Unity?

I have been developing a racing game in Unity for a few months and I can't find any information on how to simulate a car differential. Right now I just split the torque generated by the engine 50-50 ...
1 vote
112 views

### How to implement soft-body blobs that don't pass through one another

I am learning about soft-body implementations in Unity recently, and I stumbled upon the game Blob Merge 3D. It is quite an interesting implementation because the blobs do not overlap one another and ...
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1 vote
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### Physics interpolation given an asynchronous physics thread

I've followed https://gafferongames.com/post/fix_your_timestep/ to do interpolated physics. I have a separate thread entirely from my graphics thread. I use vulkan which allows me to do asynchronous ...
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1 vote
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### Separating axis theorem implementation results in limitless extending colliders along the Z axis

I am trying to implement SAT and it works except for the fact that colliders extend infinitely along the Z axis and I can never get past them. I also have confirmed that ...
1 vote