Question Simulating bounciness with Vector3.Reflect

I have a ball, a kinematic RigidBody that I'm moving manually.
I'm using Vector3.Reflect to change it's direction when it collides with other objects.
That part is working fine, I'm using a spherecast to detect collisions, then moving the ball into contact with the other object, and then using Vector3.Reflect to get the new direction, which bounces the ball perfectly:

Code (CSharp):

1. _newVelocity = Vector3.Reflect(Velocity, _normal);

However, I want to be able to control how "perfect" the new direction is - similar to how Bounciness works when letting the physics engine automatically control a Rigidbody. Where a bounciness of 1 means it perfectly retains momentum, and a value of 0 means it "sticks" to the wall but retains sideways momentum if it for example hit the wall at an angle:



Any ideas how this can be achieved?

I tried simply adding a multiplier to the _normal used in Vector3.Reflect, but it didn't work out well.
I had a 2nd idea, of "scaling" the new velocity down along the normal vector, but I have no idea how that would be written as code

 

could test what happens with Vector3.Lerp()
so could lerp between Result and that 0 angle direction

 

That's a good plan, but I'm not sure how to calculate that "0 bounciness" vector in the illustration.

The values I have are the ones written in black in the illustration. The initial velocity, the normal of the surface hit, and the resulting velocity after a perfect bounce

Edit: I figured it out after thoroughly reading through the Vector3 section on the wiki!
Had to use Vector3.ProjectOnPlane to project the new velocity onto the collision normal.

Code (CSharp):

1. Vector3 _newVelocityA = Vector3.Reflect(Velocity, _normal);
2. Vector3 _newVelocityB = Vector3.ProjectOnPlane(_newVelocityA, _normal);

Where _newVelocityA is a perfect collision angle (bounciness 1), and _newVelocityB slides perfectly along the wall (bounciness 0).
Should be able to just Vector3.Lerp between these now!