I want to place some object to real world coordinate. Is it possible? without surface detection?
2 Answers
Yes, you can place relative to another point, for example the position of the camera, i.e. the centre of the current view.
See this example, which uses the original, now depreciated Sceneform: https://stackoverflow.com/a/56681538/334402
Sceneform is now being updated and maintained here and the same basic approach will still work: https://github.com/thomasgorisse/sceneform-android-sdk
It is possible but not recommended as anchors are supposed to be attached to a trackable surface. What you can do is shoot a ray from your camera and place an anchor where the ray intersects a Trackable plane. You can set your app to do this a set number of seconds after the user starts the app (make sure to let the user know they need to look around to help in plane detection)
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