Device coordinate problem with transparency

[jwwalker]

I was experimenting with using an unlit material with vertexDomain : device to draw a background and an overlay. It mostly works, except in how it interacts with translucent objects between the overlay and the background. My test overlay has a device z of -1, and my test background has a device z of 0.9999.

As you can see in this screen shot, the textured background does not show through the translucent pink ball, though other balls do show through the pink one. And the pink one is not visible through a translucent green overlay. This is Filament 1.10.4 tested with Metal on macOS. Am I missing something, or is this a bug?

[romainguy]

Objects in the device vertex domain will still be sorted like all the other objects. You probably need to change your bounding box and/or render priority of the background and overlay.

[romainguy]

The bounding box is always in world space. But the whole point of using device coordinates is that you want the object to be visible so you might as well disable (camera) culling on it.

[jwwalker]

When I tried turning off frustum culling but not setting priorities, I still saw the problem, so apparently the bounding boxes were not the issue. But I will turn off frustum culling as well as setting priorities, to be safe. Thanks for your help!

[romainguy]

The object will be sorted, just not culled.

[jwwalker]

So, when you say it will be sorted, you mean I still need to worry about bounding boxes? Or is that only if there are multiple renderables with the same priority? I don't see how it makes sense to try to make a world-space bounding box in this situation.

[romainguy]

The bounding box will matter only if other objects have the same priority. But the bounding box can be arbitrary, it doesn't have to have any meaning in this case.