OpenXR: Allow composition layers to enable hole punching #91485
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Gave it a try, seems to work well! If I understand correctly, |
Thanks for testing!
I think it's still potentially useful, it depends on what's behind the composition layer. If there's a passthrough layer at the back, you could use |
dsnopek
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| remove_child(fallback); | ||
| fallback = nullptr; | ||
| openxr_session_running = false; | ||
| if (fallback && !_should_use_fallback_node()) { |
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Possibly safer to just do if (fallback). If there shouldn't be a fallback node, it won't have been created.
This could potentially create a leak where the fallback was created, but since then the dev disabled hole punch, so we don't remove the fallback because now the _should_use_fallback_node returns false.
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Hm. There's really no risk of a leak here, because fallback is a node that's a child of the composition layer node, so it'll automatically get cleaned whenever the composition layer node is cleaned up. And, if the dev changed the hole punch setting, it would already have gotten cleaned up in set_enable_hole_punch(). But even beyond that, if _should_use_fallback_node() now returned false, we would still clean it up, because we're checking for !_should_use_fallback_node() (negated with !) in the above code.
So, I personally think this code is fine as it is.
| @@ -212,7 +262,19 @@ void OpenXRCompositionLayer::_reset_fallback_material() { | |||
| return; | |||
| } | |||
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| if (layer_viewport) { | |||
| if (enable_hole_punch && !Engine::get_singleton()->is_editor_hint() && is_natively_supported()) { | |||
| Ref<ShaderMaterial> material = fallback->get_surface_override_material(0); | |||
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I might be reading this wrong but what happens if I need the fallback and I have hole punch enabled? Wouldn't this override the material that renders my viewport?
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No, if you were on a platform that didn't natively support composition layers and you needed the "real" fallback mesh, then this code block wouldn't run because is_natively_supported() would return false, and you'd end up in the next code block which sets up the ViewportTexture
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@BastiaanOlij @AThousandShips @m4gr3d Thanks for the review! My latest push has integrated all of your suggestions, except for two where I personally think the current code is fine - both are explained in my responses above. |
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Thanks! |
I would probably have tried to include this in PR #89880, which added the
OpenXRCompositionLayernodes, but I thought it wasn't supported by Godot's renderer, until last week @BastiaanOlij let us know about the magicalshadow_to_opacityshader render mode (and fixed it in PR #91096).This adds an
enable_hole_punchproperty onOpenXRCompositionLayerthat can enable a technique called "hole punching", which allows putting the composition layer behind the main projection layer (ie settingsort_orderto a negative value) while "punching a hole" through everything rendered by Godot so that the layer is still visible.This can be used to create the illusion that the composition layer exists in the same 3D space as everything rendered by Godot, allowing objects to appear to pass both behind or in front of the composition layer.
Anyway, given that it is a small change to a feature added in Godot 4.3, perhaps we can sneak it in?