Check all contact points for position.:

Scripting
1

Hi,
I want to check if any of the contact points of a collision are below a certain y coordinate.
I just don’t exactly know how to do that.
I looked up how to check an Array for certain values, but with the contactpoints you have to do like:

other.contacts[0].point.y

And I also couldn’t find how to check if it is below a value, only if it has a point has the exact value.

~Glemau

2

Hello,

for(int i = 0; i < other.contacts.Length; ++i)
{
    if(other.contacts[i].point.y < threshhold)
    {
        // Do stuff
    }
}
3

Now that I see this I don’t see how I didn’t find it.:slight_smile:

But would it check every single one within one frame?

4

Yes, unless you volontary skip frames by using a coroutine, it will be executed within one frame.

5

And one more Question:

I realized, that when the object is not changing its state (eg. Position) It does not show me any Contact points.
Can I manually check for Contact points, in case it is not moving?

6

You have three events available to detect collisions:

OnCollisionEnter
OnCollisionStay
OnCollisionExit

Theses are events and are not called every frames.
OnCollisionEnter will be called when the collision begin.
OnCollisionStay will be called every FixedDeltaTime (not every frame) while a collision exist.
OnCollisionExit will be called when the collision end.

Physics is not computed each frame but in a fixed Timestep you can configure yourself in Edit->Projects Settings->Time
By default it’s 0.02 (50 fps)

It’s fixed because a game’s framerate is very inconsistant and collision bugs can occure easely when the framerate drop slightly. It’s even worst with Vertical Sync.

By configuring a fixed timestep you are aware of the limitation you have to avoid collisions bugs.
Do not try to collide a car moving at 1000 km/h against a thin wall, it will just pass trough.
Imagine the fact that if the car is at 999 km/h, the detection will occure but not at 1000 km/h.
Changing the fixed timestep allow you to tweak that.
You still have to keep in mind that a lower fixed timestep take more CPU. (0.01 → 100 FPS)

7

Thank you for this extensive answer. It helped me a lot :slight_smile: