Matter-js: how should i set the max velocity so that wall does not pass through the walls?

[kushal0406]

Initially

When I press the down key for a long time. Ball becomes so fast that it goes through the wall and reaches the bottom like shown below

Also if ball strikes the borders with a high speed  it disappears and cannot be brought back.

If I set a maximum value for the velocity what should should be the max velocity? 

`document.addEventListener('keydown', event =>{

const {x,y} = ball.velocity;
if(event.keyCode === 87 || event.keyCode === 38){
console.log('Move the ball Up')
Body.setVelocity(ball, {x, y:y-5})
}
if(event.keyCode === 83 || event.keyCode === 40){
console.log('Move the ball down')
Body.setVelocity(ball, {x, y:y+5})
}
if(event.keyCode === 68 || event.keyCode === 39){
console.log('Move the ball right')
Body.setVelocity(ball, {x:x+5, y})
}
if(event.keyCode === 65 || event.keyCode === 37){
console.log('Move the ball left')
Body.setVelocity(ball, {x:x-5, y})
}
})`

[michael-garofalo]

I'm not understanding how you're setting Velocity.

There are usually four parts...
https://brm.io/matter-js/docs/classes/Body.html#method_setVelocity

• x:
• the X value
• y:
• the Y value

{ x: xSpeed, y: ySpeed }

It looks like you're setting up 4-way controls. If the ball is moving left or right, why not change the "y" speed to "0" instead?

I use Hype and Matter.js, so it might be different for me, but I usually have be specific with both X & Y values. If I only want to change the Y value, I get (getVelocity) the current X value before using setVelocity. If I simply put "x" instead of "x: 0", I get this...

ReferenceError: Can't find variable: x

Anyway, that's how I do it. While matter.js doesn't have CCD, at least not yet, if the speeds are slow enough, it should be good. Here's an example that is very similar to your project...

https://photics.com/games/picopede/

Picopede's speed is set to 2.5. You're using 5, which is faster, but doesn't seem too fast — not for Picopede. I tried setting Picopede's speed to 5 and it was OK. Perhaps the problem is that the walls are too thin. 🤔

[AsishRaju]

@michael-garofalo walls being a thin is not a problem i even tried of setting "x:0" for setting velocity when i am just moving in "y" direction but the problem mentioned by @kushal0406 still exists

I am afraid that this is a famous problem called tunneling and still an open issue since 2014,
more on this issue here #5 , sad thing is @liabru is still trying to work this out, i hope he does it.

Simulating Physics in computational world is very hard

[liabru]

As mentioned it looks like your problem is most likely a combination of:

• there's currently no CCD (I know, I know)
• bodies are too thin (make them thicker)
• bodies are too fast (slow them down)
• timestep is too large (use a smaller timestep and multiple updates per frame)

You should implement your own checks (e.g. do a ray cast) before letting the player move if possible.

I should say too though that most CCD implementations will still not be a magic bullet and will have edge cases, so unfortunately satisfying the above problems too is always recommended.

[bozhich]

With a bit thicker walls, limiting the velocity may do the trick

For example:

        const limitMaxSpeed = () => {
            let maxSpeed = 1;
            if (body.velocity.x > maxSpeed) {
                Body.setVelocity(body, { x: maxSpeed, y: body.velocity.y });
            }

            if (body.velocity.x < -maxSpeed) {
                Body.setVelocity(body, { x: -maxSpeed, y: body.velocity.y });
            }

            if (body.velocity.y > maxSpeed) {
                Body.setVelocity(body, { x: body.velocity.x, y: maxSpeed });
            }

            if (body.velocity.y < -maxSpeed) {
                Body.setVelocity(body, { x: -body.velocity.x, y: -maxSpeed });
            }
        }
        Events.on(engine, 'beforeUpdate', limitMaxSpeed);