/*

George Zhang

Class to help find closest intersecting cube.

*/

package geetransit.minecraft05.engine;

import java.util.List;

import org.joml.Vector2f;

import org.joml.Vector3f;

import org.joml.Intersectionf;

public class ClosestItem {

public float distance; // distance from camera

public Item closest;

public Vector3f hit; // position of intersection

public Vector3f direction; // points away from camera

private final Vector3f max;

private final Vector3f min;

private final Vector2f nearFar;

public ClosestItem() {

this.hit = new Vector3f();

this.direction = new Vector3f();

this.min = new Vector3f();

this.max = new Vector3f();

this.nearFar = new Vector2f();

}

public ClosestItem(List<Item> items, Camera camera) {

this();

this.update(items, camera);

}

public ClosestItem reset() {

this.distance = Float.POSITIVE_INFINITY;

this.closest = null;

return this;

}

public ClosestItem update(List<Item> items, Camera camera) {

this.reset().extend(items, camera);

return this;

}

public ClosestItem extend(List<Item> items, Camera camera) {

// get camera direction

camera.getViewMatrix().positiveZ(this.direction);

this.direction.negate().normalize();

// loop through all items

for (Item item : items) {

this.min.set(item.getPosition());

this.max.set(item.getPosition());

this.min.add(-item.getScale(), -item.getScale(), -item.getScale());

this.max.add(item.getScale(), item.getScale(), item.getScale());

// check if intersects and is closer

if (Intersectionf.intersectRayAab(

camera.getPosition(), this.direction,

this.min, this.max, this.nearFar

)) {

if (this.nearFar.x < this.distance) {

this.distance = nearFar.x;

this.closest = item;

this.hit.set(this.direction);

this.hit.mul(this.distance);

this.hit.add(camera.getPosition());

}

}

}

// allow method chaining

return this;

}

}