如何知道3D对象是否在VR中被查看

Question

我正在使用RajawaliVR库。

我已经添加了一个平面，并对其应用了纹理。知道我想知道我的物体何时被观察，这样我就可以触发一些事件。在RajawaliVR或google cardboad中有什么可以帮助我做到这一点的吗？

    Material cruiserMaterial = new Material();
    cruiserMaterial.setDiffuseMethod(new DiffuseMethod.Lambert());
    cruiserMaterial.setColorInfluence(0);
    cruiserMaterial.enableLighting(true);
    try {
        cruiserMaterial.addTexture(new Texture("spaceCruiserTex",
                R.drawable.image2));
    } catch (TextureException e) {
        e.printStackTrace();
    }

    Object3D leftPlane = new Plane(10f, 10f, 1, 1, 1);

    leftPlane.setMaterial(cruiserMaterial);
    leftPlane.setRotZ(90);

    Object3D container = new Object3D();
    container.addChild(leftPlane);
    container.setRotX(90);
    container.setRotY(90);
    container.setRotZ(90);
    container.setZ(-20);

    getCurrentScene().addChild(container);

Answer 1

只需将此代码放入渲染器主循环(OnDrawFrame)中，使用对象迭代列表并将对象作为参数传递即可。如果您当前正在查看一个对象，则该方法将返回true。

private static final float YAW_LIMIT = 0.12f;
private static final float PITCH_LIMIT = 0.12f;

/**
 * Check if user is looking at object by calculating where the object is in eye-space.
 *
 * @return true if the user is looking at the object.
 */
private boolean isLookingAtObject(WorldObject object) {
    float[] initVec = { 0, 0, 0, 1.0f };
    float[] objPositionVec = new float[4];

    // Convert object space to camera space. Use the headView from onNewFrame.
    Matrix.multiplyMM(mModelView, 0, this.getHeadViewMatrix(), 0, object.getModel().getModelMatrix().getFloatValues(), 0);
    Matrix.multiplyMV(objPositionVec, 0, mModelView, 0, initVec, 0);

    float pitch = (float) Math.atan2(objPositionVec[1], -objPositionVec[2]);
    float yaw = (float) Math.atan2(objPositionVec[0], -objPositionVec[2]);

    return Math.abs(pitch) < PITCH_LIMIT && Math.abs(yaw) < YAW_LIMIT;
}