Method begin

src/main/java/fieldbox/boxes/plugins/Viewport.java:261–275

(Window.Event<Window.MouseState> provokedBy)

				Mat4 p = camera.projectionMatrix();
				Mat4 v = camera.view();

				p.transpose();
				v.transpose();

				t = new Mat4(p).mul(v);

				f = properties.get(Box.frame);

				return true;
			}

			@Override
			public void result(List<FLinePointHitTest.Hit> hit) {

			}

			Vec3 tmp = new Vec3();