# 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.

110 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 ...
128 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 ...
45 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 ...
137 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 '...
56 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 ...
32 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 ...
248 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. ...
412 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 <= ...
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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, ...
33 views

### My orbit code produces the wrong results

I have a GameObject called "Sun" in the sky. A game object called "GameManager" keeps track of time in the game, it is responsible for updating the hours and days. For my sun I do something like this ...
19 views

### How would joints work in an impulse-based physics engine?

I want to learn about physics engines, especially impulse-based ones. So I've followed along this tutorial to create some simple rigid-body physics: http://gamedevelopment.tutsplus.com/tutorials/how-...
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### Calculating a smooth velocity of interaction touches

I have a touch game and it would be beneficial to be able to know the "velocity" of each touch on the screen. Let me explain. Right now I am already subtracting current touch position from previous ...
28 views

### How to resolve multiple simultaneous ball collisions in a pool game?

I'm trying to simulate a break shot in billiards (1 ball hits a pyramid of 15 balls). The formula for 2D ball collision works correctly in my game. But when it is applied to the break-shot, the result ...
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 ...
21 views

### 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: velocity += forces * timestep; forces = 0; position += ...
45 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 ...
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### 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 ...
42 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 ...
39 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 ...
39 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....
54 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=...
62 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 ...
70 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 ...
83 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 ...
87 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 ...
58 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 ...
129 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 ...
130 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 ...
40 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 ...
79 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,...
268 views

### Java 3D collision detection with JBullet

So I have spent a long time trying to work on a collision detection system from scratch for own game engine and came up fruitless due to lack of time. Finally I decided to try to use Jbullet to try to ...
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 ...
84 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 ...
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: ...
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....
204 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.) ...
93 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 ...
152 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 ...
231 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 ...
153 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 ...