I'm currently evaluating how feasible adding a native Oculus SDK version of Holodance is and the greatest challenge I see so far is porting our approach to loading scenes over.
The way we currently do this is based on Valve's SteamVR_LoadLevel example. In a nutshell: Set the skybox for the compositor, set a load texture in front of the player in the compositor, fade the game to the compositor, once that is done, stop rendering to VR (because the player now only sees what's in the compositor), start loading the scene and wait until it's done, do other things that could cause hiccups like prewarming shaders and a garbage collection round, start rendering to VR, fade back in. Play.
In addition to what the standard SteamVR_LoadLevel does, we render a preview of the level that is being loaded, with some text and a progress bar using Unity UI, into a RenderTexture that we also show and update on changes in the compositor. Also, to make things a little more fancy, we have several textures on quads to have our logo in 3D on several planes. Theoretically we could even animate those planes but Unity does have some hiccups while loading levels (even when using async and additive), so we don't do this.
Reviewing the API provided by Oculus Utilities for Unity 5.x
, it seems that one class we could use is OVROverlay
. Putting the texture to the right position is simply by using the Transform location and mesh primitive, right?
Then, there's OVRScreenFade
, which lets us fade ... but only to a color.
So ... it seems there are two things missing: How can we fade full to the compositor and stop rendering to VR while we are doing things what would cause framedrops?
When using SteamVR / OpenVR, this is done by calling CVRCompositor.SuspendRendering(true).