Camera.java

package com.javamarcher.systems;

import org.joml.Matrix4f;
import org.joml.Vector3f;
import org.joml.Vector4f;

import com.javamarcher.ecs.component.CameraTransform;
import com.javamarcher.window.MainWindow;

public class Camera {
	private static final Vector3f RIGHT = new Vector3f(1, 0, 0);
	private static final Vector3f UP = new Vector3f(0, 1, 0);
	private static final Vector3f FORWARD = new Vector3f(0, 0, 1);
	
	private final CameraTransform transform = new CameraTransform();
	
	private final Matrix4f viewMatrix = new Matrix4f();
	private final Matrix4f projectionMatrix = new Matrix4f();
	
	public float farPlane = 100f;
	public float nearPlane = 0.1f;
	public float fov = 60f;
	
	private final Vector3f lookAtPosition = new Vector3f();
	
	public Camera() {
		viewMatrix.identity();
		projectionMatrix.identity();
		
		calculateProjectionMatrix();
	}
	
	public void update(double dt) {
		calculateViewMatrix();
	}
	
	public void calculateViewMatrix() {
		viewMatrix.identity();
		lookAtPosition.set(transform.position).add(transform.forward);
		
		viewMatrix.lookAt(
				transform.position.x, transform.position.y, transform.position.z,	// Cam Position
				lookAtPosition.x, lookAtPosition.y, lookAtPosition.z,				// Target
				transform.up.x, transform.up.y, transform.up.z);					// Up
	}
	
	public void calculateProjectionMatrix() {
		projectionMatrix.identity();
		projectionMatrix.perspective((float) Math.toRadians(fov), getAspectRatio(), nearPlane, farPlane);
	}

	/**
	 * Returns the frustum corner vectors in this format: <br><br>
	 * 
	 * Top left corner: 		row: 1, index: 1<br>
	 * Top Right corner: 		row: 0, index: 0<br>
	 * Bottom right corner: 	row: 3, index: 3<br>
	 * Bottom left corner: 		row: 2, index: 2<br>
	 */
	public Matrix4f GetFrustumCorners() {
		final Matrix4f corners = new Matrix4f();
		corners.identity();
		
		final float halfFov = fov * 0.5f;
		final float tanFov = (float) Math.tan(Math.toRadians(halfFov));
		
		final Vector3f toRight = new Vector3f(RIGHT).mul(tanFov).mul(getAspectRatio());
		final Vector3f toTop = new Vector3f(UP).mul(tanFov).negate();
		
		final Vector3f topLeft = new Vector3f(FORWARD).sub(toRight).add(toTop).negate().normalize();
		final Vector3f topRight = new Vector3f(FORWARD).add(toRight).add(toTop).negate().normalize();
		final Vector3f bottomRight = new Vector3f(FORWARD).add(toRight).sub(toTop).negate().normalize();
		final Vector3f bottomLeft = new Vector3f(FORWARD).sub(toRight).sub(toTop).negate().normalize();
		
		corners.setRow(1, new Vector4f(topLeft, 0));
		corners.setRow(0, new Vector4f(topRight, 0));
		corners.setRow(3, new Vector4f(bottomRight, 0));
		corners.setRow(2, new Vector4f(bottomLeft, 0));
		
		return corners;
	}

	private float getAspectRatio() {
		return (float) MainWindow.WIDTH / (float) MainWindow.HEIGHT;
	}

	public CameraTransform getTransform() {
		return transform;
	}

	public Matrix4f getViewMatrix() {
		return viewMatrix;
	}

	public Matrix4f getProjectionMatrix() {
		return projectionMatrix;
	}
}