Issues with placing objects on ground in Unity

Question

In the prerelease versions of the Unity plugin, I had come up with a way to place objects at ground level. In short, raycasting from a point above the lat/lon I want, and setting the object to the hit position.

I've slightly adapted our code to work in v1.0. I can now use the EngineToGeometry() function, and a reverse I created, plus the built in mesh colliders, etc.

However, I'm having an issue I didn't have before. Our application has objects that may be added to the map or moved at any time, plus objects that are procedurally created, which get recreated when a different LOD is loaded on the map.

The main problem I'm seeing is this: while zooming in/out of the map (using the CameraController from the samples project), sometimes objects appear to move to a very different part of the map. I believe the issue stems from raycasting (placing an object) while the world tiles are updating. Perhaps the raycast hits somewhere, and I convert that Enginelocation to a Geometry location, but then the geometry moves and my object ends up at the wrong spot. I've tried moving my raycast to different times in the Unity loop (Update, FixedUpdate, LateUpdate, WaitForEndOfFrame, etc), but none of these changes has solved the problem.

Any thoughts on how to workaround this problem? Or a better approach to getting the ground position of a lat/lon altogether?

Thanks

cavajm · Answer

https://www.opentopodata.org/api/

GarrettLeach · Answer

Hey Matt,

Thanks for the reply. I have taken a look through most of the samples already, but each one seems to fall short for our use case. As I mentioned before, the routing sample fails at scale, though it's works well up close. The method of rebasing is to offset each Unity-coordinates point by the amount the universe moved. This works until the LOD starts changing significantly on the map. The shape of the terrain has changed, but the shape of the route hasn't, so the line is prone to clipping through terrain. See images Routing 1, 2, and 3. Note that I manually scaled up the line width as I zoomed out. In our app, we automatically scale the line with distance from camera.

The Feature Layer sample actually seems to exhibit the exact problem I'm seeing. Sometimes when I jump to a stadium, it ends up floating in the air above it's location. See the Stadium image. It seems like maybe the stadium loaded in on the ground while the map was in a rebasing state (my best guess for this issue).

And back to the Raycast Sample, it's hard to tell in a static image, but the text isn't offset at the programmed amount. It's hundreds of feet in the air. I attached the hittest_correct and hittest_incorrect images to hopefully make this more clear.

For now,  we have stuck with the Beta version because this functionality is working more consistently with our source code edits than in the Release version, though there are still some flaws. It seems like it would be very helpful if there were events or flags conveying the state of the world rebase, so we would know when the terrain is "ready" for an accurate raycast. That's just an idea off the top of my head without a real idea of how it's working behind the scenes, though.

As for querying the elevation, it seems like a cumbersome way to handle it with the amount of objects/lines that may be on screen at any given time.

If there is a more built-in elevation solution coming in the future, it sounds like the best option may be to wait until that gets released.

routing 1.PNG

routing 2.PNG

routing 3.PNG

stadium.PNG

hittest_correct.PNG

hittest_incorrect.PNG

Matt_Nelson · Answer

Here is the elevation api I eluded to https://open-elevation.com/