How do you make a simple method to cast rays from a box collider?

I'm trying to make a custom 2D physics controller using raycasts. I followed this tutorial and it works, but it seems like there's a lot to do for just a few things, although that might just be me (programming really isn't my strong suite). The video also combines input and gravity into one script while calculating physics and movement in another and I'd rather split those up and combine them in a way where they're not so dependent on each other, so I'm attempting to take what I learned and try to recreate just the physics from scratch starting with combining physics and gravity into one independent script.

To start things off though, I'm just trying to figure out how to cast rays from the player's box collider. The way the video does it (I think) is by making some Vector2's, making a variable that gets the colliders bounds and then I think they assign a position for each side. It seems kinda self-explanatory, but it also does seem like a lot and I'm wondering if that can be trimmed down at all. As for the actual casting of the ray, I sorta get the syntax for it, but I'm lost on how to actually cast it from the collider itself.

Sorry if this seems like unnecessary, beginner related stuff, I just tend to get a little overwhelmed by this sort of thing since it seems like there's a lot to do for something that I think would be relatively basic.

 

These two things have me scratching my head:

You're trying to remake a production physics / collision subsystem ... and you're surprised it's a lot?!

Physics systems are complex.

Any reason you're not just using the physics system that Unity gives you? Odds are it can do what you need.

 

Shows how little I know! My only other experience with platformer physics is from other engines that have most of it built-in so you only need a few lines of code at most. As for not using the physics system, the general consensus that I find is that Unity's physics don't fit the tight, platformer feel that games in the genre are known for, so most users argue that it's best to code your own. Supposedly you can pull it off with Unity's physics (there's a couple high profile games I heard of that did it), but I can't find many resources that help in that regard.

 

Agree with that... physics is not always the best solution. Now I understand what you're thinking.

As for starting the raycast exactly on the collider, that's probably not necessary.

When I've used raycasting to do my own custom platforming, I've always bound it closely to the stateful behavior, coding up specific casts for each state, like walking, jumping, attacking, etc.

It's also nice because you can put a MonoBehaviour on the platforms telling what they're made of, so from the one raycast above the player can know if he's on ice or sand or whatever.

 

No worries! I'm largely just relaying what I've heard.

Many users say that the built-in physics tend to simulate reality whereas most platformers tend to not do that, though as mentioned earlier, it's possible. I personally haven't had much success with it so far, although that could be me not knowing how to progress. I'm going for a game feel that's similar to something like Shantae/Kirby where you have full control of the player at all times and any "forces" are instantaneous (no acceleration or the like, at least for now). Best feeling jump I can get with it involves raising the gravity and jump power by quite a lot, which isn't really a bad thing, it's just not really the kind of "feel" I'm looking for. Also in my case, tapping the jump button causes the player to go way too high and I can't find a way to reduce it without slowing them down a ton. I also use 'transform.Translate' for my movement and from what I can find, that doesn't seem to work well with built-in physics. Again, it could probably be just me not knowing what to do.

Speaking of, one the main things I see for opting to go with a custom controller is that the physics system doesn't play nice with more advanced stuff like slopes or wall jumping. I don't know how true that is, my game won't have any of that anyway, so I couldn't care less. Would like to implement moving platformers and slide turns though.

This could also be part of the problem. Most tutorials I find on the matter are maybe a little too simplistic and don't go into anything beyond the basics.

 

So, after doing some research, I guess what I'm doing is using a Kinematic body to allow me greater control over things like gravity and jumping while letting the physics handle everything else. I actually managed to get some custom gravity working, but I'm unsure if the fall speed is accumulating over time or if it's staying consistent. It looks like it's consistent, but the debugger has me thinking otherwise. I'm also still trying to figure out raycasts for collision checks, which sort of brings me back to my original question.

I've managed to at least get a ray cast from the center of the player's box collider, but I'm unsure what the correct way is to use it as ground check. Last time I tried I almost got it to work, but it counted as grounded when the cast hit the ground, not the collider, which caused the player to "hover" in the air.
I'm also unsure how to cast multiple rays at once since that's a common thing for better collision detection.

Quick sidenote: the reason why I used transform.Translate is because it's the only movement option I tried that hasn't given me any issues. Everything else usually either throws an error or gives me some weird movement effect like teleporting to a new position. The only other thing that's worked so far is using Rigidbody2D.position which I guess works, but I can't move the player around in the scene view without them warping back to where they were while falling. Granted, I tried moving it to FixedUpdate after adding a Time.deltaTime to it, so maybe that's normal?

 

Took me awhile to figure it out, but I've now managed to take what code I have, changed it to use MovePosition and it's working as far as I can tell!

Still trying to figure out my initial issue though:

Update on that: I have the horizontal movement in it's own script with physics/gravity in it's own as well and it seems like movement flat out doesn't work while the physics script is active.

 

Movement script:

Code (CSharp):

1. public class Movement : MonoBehaviour
2. {
3.     public float walkSpeed = 10f;
4.     public float runSpeed = 18f;
5.  
6.     Rigidbody2D rb;
7.  
8.     void Start()
9.     {
10.         rb = GetComponent<Rigidbody2D>();
11.     }
12.  
13.     void FixedUpdate()
14.     {
15.         Walk();
16.         Run();
17.     }
18.  
19.     public void Walk()
20.     {
21.         float horizontalInput = Input.GetAxisRaw("Horizontal");
22.         rb.MovePosition(rb.position + new Vector2(horizontalInput, rb.velocity.y) * walkSpeed * Time.deltaTime);
23.     }
24.  
25.     public void Run()
26.     {
27.         if (Input.GetKey(KeyCode.LeftShift))
28.         {
29.             float horizontalInput = Input.GetAxisRaw("Horizontal");
30.             rb.MovePosition(rb.position + new Vector2(horizontalInput, rb.velocity.y) * runSpeed * Time.deltaTime);
31.         }
32.     }
33. }

Physics script:

Code (CSharp):

1. public class Physics : MonoBehaviour
2. {
3.     public float gravity = 30;
4.     public float maxFallSpeed = 30;
5.     public LayerMask groundMask;
6.     public float rayLength = 5f;
7.  
8.     [HideInInspector]
9.     public bool isGrounded;
10.  
11.     private Vector2 velocity;
12.     private Rigidbody2D rb;
13.     private BoxCollider2D hitbox;
14.  
15.     void Start()
16.     {
17.         rb = GetComponent<Rigidbody2D>();
18.         hitbox = GetComponent<BoxCollider2D>();
19.     }
20.  
21.     void Update()
22.     {
23.         RaycastHit2D raycastHit = Physics2D.Raycast(hitbox.bounds.center, Vector2.down, rayLength, groundMask);
24.         Debug.DrawRay(hitbox.bounds.center, Vector2.down * rayLength, Color.red);
25.  
26.         if (raycastHit)
27.         {
28.             isGrounded = true;
29.         }
30.         else
31.         {
32.             isGrounded = false;
33.         }
34.     }
35.  
36.    private void FixedUpdate()
37.     {
38.         if (!isGrounded)
39.         {
40.             rb.MovePosition(rb.position + (new Vector2(rb.velocity.x, -gravity) * Time.deltaTime));
41.         }
42.         else
43.         {
44.             rb.MovePosition(rb.position + (new Vector2(rb.velocity.x, 0)));
45.         }
46.     }
47. }

Few things: The Rigidbody2D is just the standard kinematic body with Continuous collision detection.
I'm fairly certain the reason why I can't move while the physics script is active has to do with the Vector2 in the FixedUpdate. I've tried a few things already, but no luck so far.
I'm pretty sure I'm also doing collisions incorrectly because it goes by the raycast and not the player's box collider. I'm assuming I have to get the colliders bounds, but I'm not sure what to do after that.
I'm aware I'm probably doing a lot of other things wrong.