# 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.

103 views

### Implementing proportional navigation in 3D

Good afternoon guys, a = N * λ' * V is the formula for the commanded acceleration required to hit the target, where N is the proportionality constant, λ' is the change in line of sight and V is ...
126 views

### 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 ...
132 views

### Everything is set to Bounciness 0 - Why am I still bouncing?

I am creating a platformer where rather than manipulating the character to get them from the beginning of the level to the end, you manipulate the world. Thus, when you want to make the character '...
53 views

### Movement & arriving using forces

3D. Given a point mass m, inital position p0 initial velocity v0, and a desired location d, how do I apply forces (with magnitude no greater then fMax) to move m to d and stop. I know how to apply ...
27 views

### In Unity3D (and PhysX), how do I calculate the products of inertia?

Since unity3d uses physx underneath the surface, obviously they share the same features. One of the features is the moment of inertia tensor - Unity3D one, PhysX one. Though, they use the diagonal ...
235 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 ...
140 views

### 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 ...
257 views

### 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. ...
411 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: impulse = desired_velocity_change * mass impulse = force * time friction_force <= ...
11 views

### Serious issues with grid of connected springs

So i have a simulation I am trying to make where there is a grid. Each dot will be connected to the dot Above, below, left, or right (If such dot exists) via a logical grid. Theoretically when I ...
12 views

### In PhaserJS, how do I get a clicked Physics.P2 body's data?

I have a sprite with Phaser.Physics.P2 enabled, using a custom shape loaded with loadPolygon() from a .json file. I have also activated its debug and debugBody properties, so I can see the custom ...
37 views

### When to Use Spatial Hashing vs Bounding Volume Hierarchy?

I've been slowly working on implementing a spatial hashing function into Bullet Physics to see how well it will work in my game engine as a general use. Though as I'm starting to design it, I do ...
44 views

### Game Physics: Calculating a collision response using the Separating Axis Theorem?

I am working on a project in which I have implemented the Separating Axis Theorem to detect collisions between objects. My current collision response is an object that contains whether it is ...
37 views

### Algorithm to propagate internal Physics force in a structure of building

Scenario: A floating structure composes of many nodes (or in more visual meaning - a cubic block). Every node is snapped to the same 3D grid. (similar to a minecraft castle) There are external ...
29 views

### Hinge/Configurable Joint rotating even if constrained

I already posted the question over on Unity forums, though, I have to say, this place often seems more professional and knowledgable, so here goes mirror post. I have a Cylinder with a Hinge and a ...
36 views

### Constant orbit using Rigidbody in Unity

I'm trying to make a few game objects (moons) orbit a planet in unity. Basically just picture a planet in the center of the screen, and a few small moons that orbit the planet with a constant velocity....
47 views

### Implementation of a quaternion based hinge constraint

I'm trying to implement a hinge joint between two rigid bodies based on Lagnange multipliers, s.t. constraint functions to be constraints on quaternions, which describe bodies orientation, itself. It'...
34 views

### Lateral Slip of car

I have been following this Gaming Institute tutorial and tried to make that car physics system in Blender Game Engine. https://www.youtube.com/watch?v=EdjUS85yVuI&list=...
56 views

### How do I simulate vehicle movement in a non-gravity environment (e.g., space)?

As a series of small experiments, I've began to tinker with game development, specifically using SpriteKit and Swift. I'm looking to simulate a body moving through a non-gravity environment, ...
37 views

### How to find or compute or look for overall/max RPM by simply checking for rotation?

I find it hard to determine the wheel RPM since I'm only making a simple 2D game of rotating object via Z-axis. I wanna try this solution but I got no change since I'm trying to find the RPM from a ...
65 views

### 2D Platform physics system with deltaTime

I'm implementing my physics handler in my own 2D "Platform" game. My main problem is that when the timestep ( deltaTime ) changes, maybe to some tiny lag spike or something like that, the running ...
77 views

### Bullet Physics: Applying a force at the point of collision

Suppose I want to simulate some kind of gripper with two "fingers" (such as pair of pliers, or two-fingered robot hand), picking up an object from the ground. Both the gripper and the object are ...
83 views

### Should I compute impact damage with energy or momentum?

My game uses physics (Box2D in particular). Just about every object in the game can be destroyed, and the primary method of combat is by slamming objects into one another at high speed. It makes ...
52 views

### Finding the components of Proportional Navigation in 2D

So, I've been scouring this, the Physics Exchange, Wikipedia, and the general web for information about Proportional Navigation, and I can't seem to wrap my head around how to find the individual ...
108 views

### Character Movement and Collision with Ragdoll Rigidbodies/Colliders?

I have a player character that I'm moving with a character controller script and it is moved by applying velocity to a Ridigbody. This works when I have a rigidbody component on the player but my ...
65 views

### How to disable static friction in Box2D?

I'm making a 2D platformer. One of the issues is that when the character hits the ground, there's an initial pause and then the character finally slows down to a halt. I believe the initial pause is ...
117 views

### Bird flight simulation (physics)

I tried to search something about bird-like animal flight simulation but it looks like everything is spammed with flappy bird 2D questions. I want to have in my 3D game bird-like animals with ...
36 views

### Collision detection for multiplayer game with MatterJS

We are developing JavaScript multiplayer top down game where characters can move freely and collide with each other. We are rather weak at mathematics and physics, luckily we don't need much, just ...
76 views

### Unity 5 Distributed Physics in Client Server Model

I have a server which controls a physics object via buttons, adding force whenever I click them. I want to be able to have a client connect and whenever the physics object has a reaction on the server,...
24 views

### Precision problem when doing collision detection?

I've got this problem, and I don't know what may be the cause of it. I finished reading this article on sphere-triangle collision. My character (the sphere) stops before it reaches the triangle, and ...
83 views

### Why doesn't my orbit form an ellipse?

I'm playing around and trying to build an orbit simulator. Unfortunately, it isn't working out to well. Instead of forming some sort of elliptical orbit, I get this: Here is the code I'm using to ...
52 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: ...
55 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....
199 views

### How do I implement realistic recovery from weapon recoil?

I want to create an equation determining how fast a gun recovers back to its center after it has fired. I have a weapon system functioning based on constants (recoil amount, bullet spread, etc.) ...
92 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 "...
62 views

### Manual response when 2 shapes made of rectangular volumes collide

I have 2 compound objects made of rectangular blocks. One of them (the one that is moving) has a script that listens to OnTrigger callbacks. What I need is to position the moving compound object on ...
149 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 ...
228 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 ...
152 views

### How do I detect collisions between a particle-based net and a ball?

I've implemented a net using Verlet integration and many points connected with constrains; like this demo, but in 3D. I want to implement collision detection between this net and a ball (like in a ...
66 views

### How to apply physics when you have sub frame state changes?

I'm currently calculating my physics every 1/100th of a second and using a state machine to manage the current state of the player. In my main loop I'm checking user input and transitioning the state ...
2k 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 ...
145 views

### PhysX - Revolute joint around unit vector

I'm using a right-handed coordinate system with (0,0,-1) = forward, (1,0,0) = right and (0,1,0) = up. PhysX version is 3.3.0. I have a unit vector which represents the axis around which my actor is ...
60 views

### Bullet Physics ConvexDecomposition?

I've looked at Bullet Physics ConvexComposition Demo and would like to implement that in my game but the code is so undescriptive and it's hard to understand what is going on. Would any of you people ...
290 views

### How do I combine multiple squares into one Tetris block?

I am learning Phaser by making a simple game—Tetris. I'm having difficulties: Can I use simple rectangles as tetrominoes or they should be sprites? I don't know how make the figure's block ...
162 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 ...
181 views

### How do you calculate the rate of rotation using the accelerometer values in Android for a particular axis?

I am developing a simple game which involves a character moving up and down only along the Y axis. Currently I am using the accelerometer readings to change the Y velocity of the character. The game ...
1k views

### Why do restitution values less than one still cause infinite bouncing in Box2D?

I'm currently trying to implement basketball bouncing into my game using Box2d (jBox2d technically), but I'm a bit confused about restitution. While trying to create the ball in the testbed first, I'...
201 views

### How do I implement a physics gun?

I'm currently trying to implement a physics gun for my game. What I want is for the entity to stay in the same position on the screen no matter how I wiggle the camera about, what is the correct way ...
156 views

### Collision shape and Model problem

I used BEPUphysics for my XNA 4.0 game , the problem is that I load my model.fbx from into the game then add it to the space of physics engine , but when I change the scaling matrix of my Model then ...
911 views

### Unity3d Gravity script issues

I'm try this script out http://wiki.unity3d.com/index.php/Gravity and I'm having some issues with it (it seemed to work when I tried it with an old version of unity) the first issue is of collision,...