ControllerColliderHit.moveDirection and ControllerColliderHit.normal

Question

I am trying to understand what the Vector3 values represent in terms of moveDirection.

As described by the API reference moveDirection is 'approximately the direction from the center of the capsule to the point we touch'

But how is a "direction" represented numerically? Is the value a particular degree of rotation, a distance between the object, or something else I haven't considered?

This question is the result of my attempt to study the code of the Unity 2D Side Scroller tutorial. In particular, this line of code:

function OnControllerColliderHit (hit : ControllerColliderHit){ if (hit.moveDirection.y > 0.01) return;

if (hit.moveDirection.y < -0.9 && hit.normal.y > 0.9) { activePlatform = hit.collider.transform; }

}

If I understand this correctly based on the context, this means that the first if statement will execute if the object collided with is above the game object (in this case the CharacterController) thus exiting the function without effect via the return command. The second if statement will execute if the object collided with is below the game object and at a certain angle. However, as I said above, I am unclear as to how these values represent direction and angle. What precisely would be the difference between a moveDirection.y value of 0.01, and a moveDirection.y value of 10? Likewise what does the value of normal represent? Is 0.9 a 90 degree angle?

Answer 1

A Vector3 is a struct of 3 floating point numbers.

Vector math is the same as it was when you first used a piece of graph paper back in school and is only different in 3D by the addition of another axis. Angles really have nothing to do with it for all that it matters.

When used to represent a direction, each number represents a delta along a coordinate system axis. The length of the diagonal from (0,0,0) to the point indicated by those three deltas is called the magnitude of the vector. A normalized vector is a vector with a magnitude of 1.

For example, if something is at the origin of the coordinate system (0,0,0) and something else were at (1,2,3), it would be 1 unit along the coordinate system's x axis, 2 units along the coordinate system's y axis and 3 units along the coordinate system's z axis. (1,2,3) is the vector representing the movement needed to move from the origin to that position. The magnitude of that movement is 3.741657, the length of the diagonal from the origin to that point.

The directions provided by your ControllerColliderHit are normalized.

In your code: If the collision point is at a direction that is no more 0.01 units along the world y axis (generally above), it will return. If the collision point is at a direction less than -0.9 units along the world y axis (mostly completely beneath) and the normal of the surface hit is pointing in a direction that is greater than 0.9 on the world y axis (almost completely up), the active platform is set to the transform whose collider was hit.

What this means is that if you hit something that is not beneath you, exit early and if you hit something that is mostly beneath you and the surface is pointing mostly up, that becomes the active platform.

ControllerColliderHit.moveDirection and ControllerColliderHit.normal

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