Checking for Grounded State with BoxCast - Platforms

(Repost from Physics)

I'm creating a 2d game with some platformer elements. I have a lot of one-way edge colliders with platform effectors, both horizontal and diagonal (for stairs). For checking if the character is grounded I use a box-cast against the terrain layer and log any hits.

The issue I'm running into is when the character is jumping through one of the one-way edge colliders there are a few brief frames where my boxcast detects the collider and registers as grounded.

My first fix was to measure the angle between the characters velocity and the normal of the collider my box-cast is detecting. If the angle is small (ex. when a player is jumping up vertically through a horizontal platform), I ignore the hit. I also make sure the velocity.y is greater than 0 because the issue only occurs for characters moving upwards.

This fixed all the cases except one. When the player's jump peaks, it's velocity becomes 0. If that happens to occur at the same time the box-cast detects a platform, it counts as being grounded... Any ideas on how to fix this? Or just a better approach?

Code (CSharp):

1.    
2. void FixedUpdate()
3.     {
4.         Rigidbody2D body = GetComponent<Rigidbody2D>();
5.         groundHits.Clear();
6.  
7.         // Are we grounded?
8.         RaycastHit2D[] potentialGroundHits = Physics2D.BoxCastAll(
9.             new Vector2(transform.position.x, transform.position.y + 0.01f),
10.             new Vector2(0.1f, 0.02f),
11.             0,
12.             Vector2.down,
13.             0.1f,
14.             LayerMask.GetMask(new string[] { "Terrain" })
15.         );
16.  
17.         foreach (RaycastHit2D hit in potentialGroundHits)
18.         {
19.             TerrainTile tileHit = hit.collider.GetComponent<TerrainTile>();
20.  
21.             // Get the normal vector associated with this tile type
22.             Vector2 normal = Vector2.up;    // Default is flat
23.             if(tileHit.type == TerrainTile.Type.StairsAsc)
24.             {
25.                 normal = new Vector2(-0.7f, 0.7f);
26.             }
27.             else if(tileHit.type == TerrainTile.Type.StairsDesc)
28.             {
29.                 normal = new Vector2(0.7f, 0.7f);
30.             }
31.  
32.             Vector2 normVelocity = Vector2.ClampMagnitude(body.velocity, 1.0f);
33.             float deltaAngle = Vector2.Angle(normVelocity, normal);
34.  
35.             // If our velocity is close to the normal vector of this surface, ignore it
36.             // (This is to handle when your jumping through a platform)
37.             if (normVelocity.y > 0 && deltaAngle < 60)
38.             {
39.                 Debug.Log("V=" + normVelocity + " N=" + normal + " DA=" + deltaAngle);
40.                 continue;
41.             }
42.  
43.             groundHits.Add(hit);
44.         }
45.     }
46.  

 

Perfecto! Many thanks.