Get current upwards velocity and set it to zero.

I'm trying to implement a double jump in my 3D platformer. At the beginning of each jump I would normally set velocity.y to zero, solving my issue, however my controller has the ability to walk up walls, therefore making velocity.y not what it normally would be. Based on this code, how would I zero out the current upwards velocity based on the normal of a surface at the beginning of a jump, allowing me to properly double jump?

Code (CSharp):

1. void Jump(Vector3 gravity) {
2.         Vector3 jumpDirection;
3.         if (OnGround) {
4.             jumpDirection = contactNormal;
5.         }
6.         else if (OnSteep) {
7.             jumpDirection = steepNormal;
8.             jumpPhase = 0;
9.         }
10.         else if (maxAirJumps > 0 && jumpPhase <= maxAirJumps) {
11.             if (jumpPhase == 0)
12.             {
13.                 jumpPhase = 1;
14.             }
15.             jumpDirection = contactNormal;
16.         }
17.         else {
18.             return;
19.         }
20.  
21.         stepsSinceLastJump = 0;
22.         jumpPhase += 1;
23.         float jumpSpeed = Mathf.Sqrt(2f * gravity.magnitude * jumpHeight);
24.         jumpDirection = (jumpDirection + upAxis).normalized;
25.         float alignedSpeed = Vector3.Dot(velocity, jumpDirection);
26.         if (alignedSpeed > 0f) {
27.             jumpSpeed = Mathf.Max(jumpSpeed - alignedSpeed, 0f);
28.         }
29.         velocity += jumpDirection * jumpSpeed;    
30.     }

 

Dot product with normal and velocity, then subtract from original velocity, I believe?

 

It wasn't quite what I was looking for but it did lead me in the right direction, so thank you. This was the code I ended up using:

Code (CSharp):

1. velocity = velocity - Vector3.Project(velocity, transform.up);