Simple rigid body collision reaction

In summary, the speaker is developing a physics engine for a game and has been using a simple method for inter object collisions. However, they have now realized that using forces and impulses is a better approach and have had a discussion with a friend about Newton's third law and the concept of a collision surface. They are seeking assistance in determining the correct impulse to apply to colliding objects and are also concerned about an issue with their current model where objects can still be interpenetrating after being moved in the next frame. They are considering adapting their current approach to move objects based on the collision surface.
  • #1
Nanako
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Simple rigid body collision reaction (Newton III)

Hi everyone! I'm writing a physics engine as part of a game I'm making. Up until this point I've implemented inter object collisions in a rather quick and dirty manner. Whenever something moves into something else, it is simply teleported back out to the edge. This implementation worked for a while, but amongst other problems, it causes anything not currently moving to be an immovable object, which is not good.

I already have written support for forces and impulses (and friction), and i believe this is the more correct way to go. I had a long discussion with a friend who educated me a bit on the subject. I understand that Newton's third law is integral here. that any two colliding objects have an equal(but opposite) impulse applied to them, and that this impulse is dependant on their relative masses and velocities

he also talked a lot about the concept of a collision surface, which is something i didn't get quite as well. I understand it to be a point between the two objects, that is weighted according to their masses, and that travels in a straight ttrajectory

At this point, i feel that I've got a handle on the basics. I'm not certain exactly what to do, but i feel i'd be able to understand it if i had a little more help . So i come to you wonderful people hoping for a little assistance in that regard.

essentially, i need to figure out what impulse to apply to a colliding pair of objects.

in addition, there's a problem that i don't fully understand. I've designed my engine using what i now now to be the A posteriori (Discrete) model, which means that it processes things in discrete frames, moving all objects, resolving collisions and altering velocities, before moving them again at the start of the next frame.

An issue i see with this model is that when two objects collide, they are inside each other. And if I'm going to be using impulses to move them out again, there does seem to be the possibility of them not colliding with enough energy, so that the impulse isn't strong enough, so that the objects are STILL interpenetrating after being moved in the next frame. This would lead to the impulse being applied multiple times, which is not good. I'm wondering if it would be best to keep my current approach of teleporting things out as well, but adapt it to move the objects to relative positions based on the collision surface (essentially fastforwarding their motion through however many frames it would take to make them stop colliding). does that make sense or seem bad ?

Any advice in these matters is appreciated.
 
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  • #2
bump! can anyone help? maybe i should have tried the general physics forum :(
 

1. What is a simple rigid body collision reaction?

A simple rigid body collision reaction is a physical phenomenon where two objects collide and exert forces on each other, causing them to change direction or speed. This reaction follows the laws of conservation of momentum and energy.

2. What factors affect the outcome of a simple rigid body collision reaction?

The outcome of a simple rigid body collision reaction can be affected by factors such as the mass and velocity of the objects involved, the angle and point of impact, and the elasticity of the objects.

3. How is momentum conserved in a simple rigid body collision reaction?

Momentum is conserved in a simple rigid body collision reaction as the total momentum of the objects involved before the collision is equal to the total momentum after the collision. This means that the combined mass and velocity of the objects remain constant.

4. What is the difference between an elastic and an inelastic collision?

In an elastic collision, the total kinetic energy of the objects involved is conserved, meaning that there is no loss of energy. In an inelastic collision, some of the kinetic energy is converted into other forms of energy, such as heat or sound, resulting in a loss of energy.

5. How is the coefficient of restitution related to a simple rigid body collision reaction?

The coefficient of restitution is a measure of the elasticity of an object. It is related to a simple rigid body collision reaction as it determines the amount of kinetic energy that is conserved or lost during the collision.

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