OpenXR ext FBpassthough : How to use Silk.NET.openXR.Extensions.FB

[courgeon]

Hello there !

I'm trying to use FB passthrough using OpenXR/OpenGL bindings.
So far, the OpenGL/OpenXR pipeline is in place, I can use Meta OpenXR and render Opaque VR in my Quest 3 using Meta Link.

However, i'm trying to use passthrough functionnality. Meta don't seem to support blend mode AlphaBlend (like Varjo XR does at least), but from what i understand, it have a dedicated API that is declared in Silk.NET.openXR.Extensions.FB.

Using Meta's C++ example, I have a base code as reference, but it seems some xr fonctions are missing in my openxr_loader DLLs

I start with

var FB_PT = new FBPassthrough(FBPassthrough.CreateDefaultContext(new[] { "openxr_loader" }));

then

result = FBPassthroughOverloads.CreatePassthroughFB(FB_PT, session...)

this command results in a dll problem as native function are not present in the dll.
Silk.NET.Core.Loader.SymbolLoadingException : 'Native symbol not found (Symbol: xrCreatePassthroughFB)'

I don't know where to go from here. Can anybody provide some insight ?

Thank you !

M.

[Perksey]

You should use xr.TryGetExtension(out FBPassthrough passthrough) instead

[courgeon]

Thanks for the quick reply :)

TryGetExtension does not seem to exists (?), the closest thing I got is this :

Xr.TryGetInstanceExtension("XR_FB_passthrough", xrInstance, out FBPassthrough FB_PT)

I use the name "XR_FB_passthrough" as it's in the EnumerateInstanceExtensionProperties result, then passed in the InstanceCreateInfo>EnabledExtensionNames

However, TryGetInstanceExtension return false, thus FB_PT is null

[courgeon]

OK ! got it. if it may it help somebody someday :

The proper extension access is actually :

Xr.TryGetInstanceExtension<FBPassthrough>(null, xrInstance, out var FB_PT);

M.

[Perksey]

Ah yeah sorry, forgot Vulkan and OpenXR are dfferent here. Glad you worked it out :)i

[courgeon]

no problem. Your answer helped me a lot anyway :)