在ARCore的Sceneform中如何在两个锚点之间绘制线条？

Question

我想在ArFragment上使用Sceneform连接两个TransformableNode，并绘制一些可见的线条，但不使用OpenGL函数。在ARCore Java中，是否可以在Sceneform中在两个锚点（或节点）之间绘制一条线？如果可能的话，我该如何实现？

- Grogzon

Answer 1

是的，有一种方法可以实现这个功能：

private void addLineBetweenHits(HitResult hitResult, Plane plane, MotionEvent motionEvent) {

    int val = motionEvent.getActionMasked();
    float axisVal = motionEvent.getAxisValue(MotionEvent.AXIS_X, motionEvent.getPointerId(motionEvent.getPointerCount() - 1));
    Log.e("Values:", String.valueOf(val) + String.valueOf(axisVal));
    Anchor anchor = hitResult.createAnchor();
    AnchorNode anchorNode = new AnchorNode(anchor);


    if (lastAnchorNode != null) {
        anchorNode.setParent(arFragment.getArSceneView().getScene());
        Vector3 point1, point2;
        point1 = lastAnchorNode.getWorldPosition();
        point2 = anchorNode.getWorldPosition();

    /*
        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());
        MaterialFactory.makeOpaqueWithColor(getApplicationContext(), new Color(0, 255, 244))
                .thenAccept(
                        material -> {
                            /* Then, create a rectangular prism, using ShapeFactory.makeCube() and use the difference vector
                                   to extend to the necessary length.  */
                            ModelRenderable model = 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 . */
                            Node node = new Node();
                            node.setParent(anchorNode);
                            node.setRenderable(model);
                            node.setWorldPosition(Vector3.add(point1, point2).scaled(.5f));
                            node.setWorldRotation(rotationFromAToB);
                        }
                );
        lastAnchorNode = anchorNode;
    }
}

- Shubham Agrawal

Answer 2

用圆柱体绘制一条线的另一种方法。

private void addLineBetweenPoints(Scene scene, Vector3 from, Vector3 to) {
        // prepare an anchor position
        Quaternion camQ = scene.getCamera().getWorldRotation();
        float[] f1 = new float[]{to.x, to.y, to.z};
        float[] f2 = new float[]{camQ.x, camQ.y, camQ.z, camQ.w};
        Pose anchorPose = new Pose(f1, f2);

        // make an ARCore Anchor
        Anchor anchor = mCallback.getSession().createAnchor(anchorPose);
        // Node that is automatically positioned in world space based on the ARCore Anchor.
        AnchorNode anchorNode = new AnchorNode(anchor);
        anchorNode.setParent(scene);

        // Compute a line's length
        float lineLength = Vector3.subtract(from, to).length();

        // Prepare a color
        Color colorOrange = new Color(android.graphics.Color.parseColor("#ffa71c"));

        // 1. make a material by the color
        MaterialFactory.makeOpaqueWithColor(getContext(), colorOrange)
                .thenAccept(material -> {
                    // 2. make a model by the material
                    ModelRenderable model = ShapeFactory.makeCylinder(0.0025f, lineLength,
                            new Vector3(0f, lineLength / 2, 0f), material);
                    model.setShadowReceiver(false);
                    model.setShadowCaster(false);

                    // 3. make node
                    Node node = new Node();
                    node.setRenderable(model);
                    node.setParent(anchorNode);

                    // 4. set rotation
                    final Vector3 difference = Vector3.subtract(to, from);
                    final Vector3 directionFromTopToBottom = difference.normalized();
                    final Quaternion rotationFromAToB =
                            Quaternion.lookRotation(directionFromTopToBottom, Vector3.up());
                    node.setWorldRotation(Quaternion.multiply(rotationFromAToB,
                            Quaternion.axisAngle(new Vector3(1.0f, 0.0f, 0.0f), 90)));
                });
    }

- Andrew G

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我们能否使用圆柱体添加虚线，或者建议可能的方法？ - Zar E Ahmer

嗨@ZarEAhmer，你能画虚线吗？ - Khawaja Absar