Update the passthrough documentation to reflect the changes in Godot 4.3 #9311
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BastiaanOlij
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Ok added the chapter |
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@DanielSnd any chance you have a screengrab of your AR project we can use to show the use of shadow to opacity? |
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I can take one with a "on/off" comparison. |
Yup, but I didn't know how to do that so some advise here is welcome :) |
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Still todo before this can be merged:
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Took a few screenshots today, are those good? I can try taking it differently if you have something specific in mind. |
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Thanks @DanielSnd , I added the middle one in. The hand is really cool but I think its harder to see what is going on. Just with the desk in front of the pitstop while there are some aliens standing on the desks... Shame we didn't have shadows working properly yet :) |
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Ok, also added the redirect, I don't know if I did this right or how to test it, but it's in there :) |
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tutorials/xr/ar_passthrough.rst
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| - The rendered image is added to the real world. This mode generally applies to AR only devices | ||
| such as the Hololens where the optics are not able to obscure the real world. | ||
| This will turn on passthrough if passthrough is used. | ||
| * - XR_ENV_BLEND_MODE_ALPHA_BLEND | ||
| - The rendered image is alpha blended with the real world. | ||
| This is supported on devices that can fully obscure the real world | ||
| and generally the preferred way to do AR. |
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Following up on my comment about terminology confusion, the use of AR only devices and AR throughout can get confusing to developers new with the apis, capabilities.
My suggestion would be that we use the terms see-through devices to refer to devices like Magic Leap, Hololens, and video passthrough devices to refer to devices like Quest, HTC Elite; unless OpenXR has another term for how to refer to either types of devices.
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I agree on the two term, I'll see what I can write better to make good use of those terms.
On a whole though it is important to note that this part of the documentations main goal is to create a foundation where it shouldn't matter whether AR is created with see-through devices or video passthrough devices, so that if you stick to this guide you create an application that works on any AR device.
The moment you start looking at APIs that only work on a subset of devices, or often just work for one vendor, that has to be a conscious choice on the developer. "Is using this feature worth tying myself into this eco system".
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Ok, rewrote part of this section, let me know if you agree with the changes.
tutorials/xr/ar_passthrough.rst
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| This is supported on devices that can fully obscure the real world | ||
| and generally the preferred way to do AR. |
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The sentence is a bit confusing; the first section states This is supported on devices that can fully obscure the real world leading to the assumption it's only supported on video-passthrough devices.
But the second section asserts this is generally the preferred way to do AR, leading to the assumption it can be used on both types of devices.
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I think that is an assumption on your part, there are see-through devices that can fully obscure the real world.
tutorials/xr/ar_passthrough.rst
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| It is advisable to do the same with ``XR_ENV_BLEND_MODE_ADDITIVE`` however here you | ||
| can alternatively set your background color to black. |
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This seems to assume that XR_ENV_BLEND_MODE_ADDITIVE is only used on see-through devices (otherwise setting the background color to black would hide the real world on video-passthrough devices) but we don't mention it so in the section above.
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Additive will add the color, and as with black you are adding zeros to whatever is underneath, you'll just see the real world. So if this is implemented properly on video passthrough, you should still see the background, it should not turn the background black.
Alpha in this case is ignored and in there lies a minor danger if you're relying on alpha as colors will actually be brighter than you expect.
Actually thinking about this now, I think I should say exactly that here and just recommend the user sets the background to black, and leave it there.
In reality, a device reporting whether it supports additive, or alpha, or both, is what informs you about the limitation of the AR technology being used and whether you as a developer want to do something with that (in many cases you don't and just accept the limitation).
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Ok, changed this, let me know what you think.
| Some AR SDKs do provide ambient lighting information or even provide a full radiance | ||
| map to allow for real world reflections in your virtual objects. | ||
| The core Godot XR functionality doesn't currently have support for this, however this | ||
| functionality can be exposed through plugins. |
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Note sure if this is relevant to this documentation.
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As more and more vendors are working on this, and it is a question I've been asked a few times, I think it is handy to have a reference to this. But maybe it's overkill :)
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We had some major changes in the way we handle AR and passthrough in Godot 4.3, this PR updates the documentation to reflect this.
The page has also been changes from an OpenXR centric page to more core focussed documentation. I don't know if there is a way once this becomes stable that it redirect the old page to the new?