在3D空间中获取与相机视图对齐的点

Question

I am trying to use Frustum to detect whether or not an object is within a square part of the screen (see image below) It's a UI image working as the aimbox not a 3D object.

The original post is here: Detect if an object in 3D space is within/touches a UI image's bounds

Right now I can get the Frustum and drawing the box to work, but only looking in one direction.

I need to be able to calculate new points when the camera turns and I can't figure out how.

The code below kinda works, but I need to offset the positions so they align with the view when the camera is moving.

Edit: Right now nothing is supposed to happen but drawing the box and get that to work. Collision detection comes after.

// Draw aimbox
Vector3 camPosOffset = camPos + cam.transform.forward * maxDistance;

float frustumHeight = (2.0f * maxDistance * Mathf.Tan(cam.fieldOfView * 0.5f * Mathf.Deg2Rad));

cubeVerts[0] = new Vector3(camPos.x, camPos.y, camPos.z);
cubeVerts[1] = new Vector3(camPos.x, camPos.y, camPos.z);
cubeVerts[2] = new Vector3(camPos.x, camPos.y, camPos.z);
cubeVerts[3] = new Vector3(camPos.x, camPos.y, camPos.z);
cubeVerts[4] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z);
cubeVerts[5] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z);
cubeVerts[6] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z);
cubeVerts[7] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z);

for (int i = 0; i < edges.Length; i += 2)
{
    Debug.DrawLine(cubeVerts[edges[i]], cubeVerts[edges[i + 1]], Color.red);
}

https://imgur.com/iXQlE04

Answer 1

Simplest version: Make the aimbox a child of the camera.

Alternative Solution, use camPosOffset also for the first 4 verts like this:

cubeVerts[0] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z);
cubeVerts[1] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z);
cubeVerts[2] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z);
cubeVerts[3] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z);
cubeVerts[4] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z) + cam.forward * 3;
cubeVerts[5] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y + frustumHeight, camPosOffset.z) + cam.forward * 3;
cubeVerts[6] = new Vector3(camPosOffset.x - frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z) + cam.forward * 3;
cubeVerts[7] = new Vector3(camPosOffset.x + frustumHeight, camPosOffset.y - frustumHeight, camPosOffset.z) + cam.forward * 3;

Answer 2

After fiddling for almost two days I got exactly what I wanted.

        //Draw aimbox

    float frustumHeight = ((2.0f * maxDistance * Mathf.Tan(cam.fieldOfView/20 * 0.5f * Mathf.Deg2Rad))); //cam.fieldOfView/20, I divide by 20 because I only need a small square of the view

    cubeVerts[0] = cam.transform.position + cam.transform.forward * 25; //25 is the distance from the camera to the object it follows
    cubeVerts[1] = cam.transform.position + cam.transform.forward * 25;
    cubeVerts[2] = cam.transform.position + cam.transform.forward * 25;
    cubeVerts[3] = cam.transform.position + cam.transform.forward * 25;
    cubeVerts[4] = cam.transform.position + (cam.transform.right * -frustumHeight) + (cam.transform.up * frustumHeight) + (cam.transform.forward * maxDistance);
    cubeVerts[5] = cam.transform.position + (cam.transform.right * frustumHeight) + (cam.transform.up * frustumHeight) + (cam.transform.forward * maxDistance);
    cubeVerts[6] = cam.transform.position + (cam.transform.right * -frustumHeight) + (cam.transform.up * -frustumHeight) + (cam.transform.forward * maxDistance);
    cubeVerts[7] = cam.transform.position + (cam.transform.right * +frustumHeight) + (cam.transform.up * -frustumHeight) + (cam.transform.forward * maxDistance);

    for (int i = 0; i < edges.Length; i += 2)
    {
        Debug.DrawLine(cubeVerts[edges[i]], cubeVerts[edges[i + 1]], Color.red);
    }

Here the altered frustum view follows the camera at any given time.