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Distance between game object and ground in Unity

I recently started having a look at game development with Unity and was trying to make a simple 2D character with basic movement abilities. This character is supposed to jump and move from side to side, but only if it is standing on something.
Now my question is: How do you check if a player is standing on something? / Get the distance to the next game object / collider beneath the player game object?
Would greatly apreciate any helpful answers and especially explanations on how exactly it works. Thanks!

To do this, you need to send a ray to detect the point of impact on the ground and then calculate the distance. The code below sends a ray from the center of your object down to the maximum height (3) and gives the size.
public LayerMask groundLayer;
public float maxRayLength = 3;
public void Update()
{
var hit = Physics2D.Raycast(transform.position, Vector3.down, maxRayLength, groundLayer.value);
if (hit) Debug.Log(hit.distance); // it will print current distance from pivot
}
If you want to calculate the height of the ray from the character's foot, there are two methods, one is subtracting half the height of the character from it.
Physics2D.Raycast(transform.position-transform.up*height, ....)
Next one is to use an empty object at the base of the character, which we refer to instead of the center.
public Transform pivot;
Then..
Physics2D.Raycast(pivot, ....)

There are a few ways of actually doing this.
The most usual although a bit complicated way of doing it for a beginner is using Raycasts. A Raycast is basically a small invisible line that starts and ends where you tell it to. If anything of a specific tag or layer is caught in it's crossfire you can basically pull that object from your code. Raycasts are used for a lot of things, most notably in Shooter games to shoot or in games like Skyrim to pickup objects and interact with them.
Another way to do this, which is a bit more popular in 2D games is to create a "feet" GameObject and make it the child of the player in the hierarchy. You can add a box collider on that GameObject and check the "IsTrigger". You can add a Tag to your ground objects and through your code using the OnTriggerEnter() and OnTriggerExit() Methods you can basically tell when your character is floating on air and when he is on ground.
Another popular method is to use the Physics.OverlapBox() Method which is pretty much the same as the Trigger Method but you are creating an invisible box (much like a raycast) and instead of only getting notified when Triggered (something enters or exits) you check if the invisible box is colliding with another object/tag/collider (which could be your ground).
There are also a few different things you can do with a Nav Mesh (mostly in 3D) but I think that for now these 3 should suffice!

Looking for a way to make a cube in which game objects bounce around

My question is quite simple. How do I make a cube which has other game objects inside of it, and can detect when those objects collide with sides of the cube. I can just use a collider for each of the sides but I want to be able to shrink and grow the cube while the program is running. If I used a collider for each of the sides I would have to move each of them individually. Is there a way to use just one collider on the cube?

Place six flat cubes around with a thin collier box and then make parent them to an empty game object.

Networked AR Unity can't make a bullet a child of the ground plane stage

I am trying to make an AR game and am currently using Unity's high-level networking classes. I have set my player prefab to be spawned in one of the two network spawn locations, which are both childs of the Ground Plane Stage. When user has tapped to make their ground plane stage and has tapped to be the host, their player character appears. Unfortunately, if they press the fire button, the bullets appear above the stage and unscaled, meaning they aren't parented to the stage. This confuses me because I've checked many times and the bullet emitter is a child of the player, and in my code it references said emitter. Thus I'm rather confused why the bullets don't seem parented.
I've attempted to attach a script to make the bullet emitter a child of the player when it spawns. I've also tried making it a child of the stage when it spawns. I've tried making the player character not dependent on the Network manager spawning it when the player joins, but then that leads to other networking problems when it comes to controlling the character, but it can shoot then.
The only one that was relatively successful was making the bullet a child of the stage when it spawned, but it would only stay in one place. Attempting to make the bullet a child of the player did nothing
//This is the class I'm trying to use to make the object a child of
something
public class AddToBeetle : MonoBehaviour
{
// Start is called before the first frame update
void Start()
{
GameObject player =
GameObject.FindGameObjectWithTag("Player");
transform.SetParent(beetle.transform, false);
}
}
It rarely prints any error messages. I hope that I can eventually get the bullet to spawn in front of the player model when the button is pressed.

Oh gosh I was dumb, the one thing I didn't apply the script to was the player's bullet emitter. It was super late and that's probably why I missed trying it on that. Anyway I hope this helps someone else if they ever have to deal with AR and Unity.

Unity Player Collider does not work properly

I have not worked with unity in a while so I am a little rusty.
I have:
Game Object with a mesh Collider which is my ground
A Empty Game Object with a Character Controller Which holds my player game objects
My Empty Game Object that holds a player doesnt not stand on top of the ground.
So half my player is going through the ground but the Empty Game Object stays ontop of the ground which holds my character.

Possible problem with pivot of 3d model(Character)
With your current heirarchy structure: One possible solution is to make Center:y = -1.8 in the character controller component.
Let me know if it helps.

making my player sprite land on top of my platform sprite

in my XNA game(im fairly new to XNA by the way) i would like to have my player sprite land on top of a platform. i have a player sprite class that inherits from my regular sprite class, and the regular sprite class for
basic non playable sprite stuff such as boxes, background stuff, and platforms. However, i am unsure how to implement a way to make my player sprite land on a platform.
My player Sprite can jump and move around, but i dont know where and how to check to see if it is on top of my platform sprite.
My player sprites jump method is here
private void Jump()
{
if (mCurrentState != State.Jumping)
{
mCurrentState = State.Jumping;
mStartingPosition = Position;
mDirection.Y = MOVE_UP;
mSpeed = new Vector2(jumpSpeed, jumpSpeed);
}
}
mStartingPosition is player sprites starting position of the jump, and Position is the player sprites current position. I would think that my code for checking to see whether my player sprite is on top of my platform sprite. I am unsure how to reference my platform sprite inside of the playersprite class and inside of the jump method.
i think it should be something like this
//platformSprite.CollisonBox would be the rectangle around the platform, but im not
//sure how to check to see if player.Position is touching any point
//on platformSprite.CollisionBox
if(player.Position == platformSprite.CollisionBox)
{
player.mDirection = 0;
}
Again im pretty new to programming and XNA, and some of this logic i dont quite understand so any help on any of it would be greatly appreciated:D
Thanks

If player.Position is a Point and CollisionBox is a Rectangle, you could use
if (platformSprite.CollisionBox.Contains (player.Position))

I was playing around with something like this just a few days ago.
What you're calling a CollisionBox I called a BoundingBox. A BoundingBox is a Rectangle which represents the area occupied by the sprite.
You'll probably find it helpful to define a BoundingBox for your sprites instead of just using their position.
You can easily test for the collision of Rectangles using the following code:
if (player.BoundingBox.Intersects(platform.BoundingBox)
{
// handle collision here...
}
For this to work, make sure that the X and Y coordinates of your BoundingBox are correctly reflecting your sprite's position.

You may want to look at the Platformer Starter Kit. It includes this as well as detecting when the player is touching an enemy, collecting gems, etc.

The answer about BoundingBox is right, but IMHO it is easier to use Rectangle if you are making a 2D game rather than BoundingBox, wich is designed for a 3D one.
Anyway both objects have intersection / collision test methods that takes Vector2 or Point as parameter.
Now you have to have a box for your player, and a box for your platform. If one collide with the other, you have to check from where (the player can hit the platform from up, down, left, right, or maybe up & left on the left up corner).
If the player is on top of the platform, then just stop his fall, probably by setting his Y-speed component to 0.
Maybe you will need the player to go through the platform when jumping (player hit from bottom) but not when falling (player hit from top).