android - 如何使用 ARCore 在平面上绘制线/折线

Question

在Java ARCore Hello AR示例中，我们可以通过点击屏幕将Android对象放置在平面上，我们如何使用这个HitResult的信息来画线在这些对象之间？

感谢您的帮助!

Answer 1

在您抓取 anchor 以放置对象的代码部分，您应该检查您是否已经有一个先前的 anchor 。如果你有一个以前的 anchor ，从以前的和当前的 anchor 中获取 worldPosition(作为 Vector3 对象)，然后计算它们之间的差异，并创建一条长度相同的线，并将它附加到两个之间的中间点的场景点。最后，将 previousAnchor 设置为当前 Anchor。

这是我用来解决这个问题的一些代码:

// Create the Anchor.
Anchor anchor = hitResult.createAnchor();
AnchorNode anchorNode = new AnchorNode(anchor);

// Code to insert object probably happens here

if (lastAnchorNode != null) {
    Vector3 point1, point2;
    point1 = lastAnchorNode.getWorldPosition();
    point2 = anchorNode.getWorldPosition();
    Node line = new Node();

    /* First, find the vector extending between the two points and define a look rotation in terms of this
        Vector. */

    final Vector3 difference = Vector3.subtract(point1, point2);
    final Vector3 directionFromTopToBottom = difference.normalized();
    final Quaternion rotationFromAToB =
          Quaternion.lookRotation(directionFromTopToBottom, Vector3.up());

    final Renderable[] lineRenderable = new Renderable[1];

    /* Then, create a rectangular prism, using ShapeFactory.makeCube() and use the difference vector
       to extend to the necessary length.  */

    MaterialFactory.makeOpaqueWithColor(this, color)
          .thenAccept(
                  material -> {
                      lineRenderable[0] = ShapeFactory.makeCube(new Vector3(.01f, .01f, difference.length()),
                              Vector3.zero(), material);
              });

    /* Last, set the world rotation of the node to the rotation calculated earlier and set the world position to
       the midpoint between the given points . */
    line.setParent(anchorNode);
    line.setRenderable(lineRenderable[0]);
    line.setWorldPosition(Vector3.add(point1, point2).scaled(.5f));
    line.setWorldRotation(rotationFromAToB);
}

lastAnchorNode = anchorNode;