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OSGText Issues: Difference between revisions
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https://sourceforge.net/p/flightgear/mailman/message/37148949/
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Linux distros provide decently recent version of OSG, which means, flightgear in distro is currently broken by this. Indeed, if even OSG-3.4.1 is breaking the text animation, look how many distros are distributing flightgear already broken (as linked to the distributed OSG)<ref>https://sourceforge.net/p/flightgear/mailman/message/37149005/</ref>: https://repology.org/project/openscenegraph/versions | Linux distros provide decently recent version of OSG, which means, flightgear in distro is currently broken by this. Indeed, if even OSG-3.4.1 is breaking the text animation, look how many distros are distributing flightgear already broken (as linked to the distributed OSG)<ref>https://sourceforge.net/p/flightgear/mailman/message/37149005/</ref>: https://repology.org/project/openscenegraph/versions | ||
If we go to OSG 3.6, they are broken, plain and simple.<ref>https://sourceforge.net/p/flightgear/mailman/message/37148949/</ref> | |||
So we need to do some Real Work (TM) to support Canvas with osgText 3.6 and upwards, unfortunately.<ref>https://sourceforge.net/p/flightgear/mailman/message/36730965/</ref> | So we need to do some Real Work (TM) to support Canvas with osgText 3.6 and upwards, unfortunately.<ref>https://sourceforge.net/p/flightgear/mailman/message/36730965/</ref> | ||
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== Background == | == Background == | ||
With OSG 3.6, Aircraft {{tag|text}} animations will be broken <ref>https://sourceforge.net/p/flightgear/mailman/message/36240313/</ref> however: that’s the blocking issue stopping us moving to 3.6 everywhere. <ref>https://sourceforge.net/p/flightgear/mailman/message/37147614/</ref> OSG 3.6 has the text display issue <ref>https://sourceforge.net/p/flightgear/mailman/message/37126793/</ref>, currently osgText doesn't work under the ALS pipeline. <ref>https://sourceforge.net/p/flightgear/mailman/message/37042335/</ref> one issue that seems to occur in a few places is missing text elements on cockpit devices ... There are [https://sourceforge.net/p/flightgear/mailman/flightgear-devel/thread/1362c1cf-e0e7-3774-da92-63b2720aab7f%40gmail.com/#msg36702528 issues with osgText not working in OSG > 3.4.2]. We need to find a migration solution for osgText that works with Compositor and newer OSG versions <ref>https://sourceforge.net/p/flightgear/mailman/message/37047567/</ref> ... another option was creating a Canvas for each text animation, but creating a FBO for every small piece of text doesn't sound very performance-friendly. <ref>https://sourceforge.net/p/flightgear/mailman/message/37042457/</ref> We need to find some way to approximate with the old OSG text did<ref>https://sourceforge.net/p/flightgear/mailman/message/37042476/</ref> | With OSG 3.6, Aircraft {{tag|text}} animations will be broken <ref>https://sourceforge.net/p/flightgear/mailman/message/36240313/</ref> however: that’s the blocking issue stopping us moving to 3.6 everywhere. <ref>https://sourceforge.net/p/flightgear/mailman/message/37147614/</ref> OSG 3.6 has the text display issue <ref>https://sourceforge.net/p/flightgear/mailman/message/37126793/</ref>, currently osgText doesn't work under the ALS pipeline. <ref>https://sourceforge.net/p/flightgear/mailman/message/37042335/</ref> one issue that seems to occur in a few places is missing text elements on cockpit devices ... There are [https://sourceforge.net/p/flightgear/mailman/flightgear-devel/thread/1362c1cf-e0e7-3774-da92-63b2720aab7f%40gmail.com/#msg36702528 issues with osgText not working in OSG > 3.4.2]. We need to find a migration solution for osgText that works with Compositor and newer OSG versions <ref>https://sourceforge.net/p/flightgear/mailman/message/37047567/</ref> ... another option was creating a Canvas for each text animation, but creating a FBO for every small piece of text doesn't sound very performance-friendly. <ref>https://sourceforge.net/p/flightgear/mailman/message/37042457/</ref> We need to find some way to approximate with the old OSG text did<ref>https://sourceforge.net/p/flightgear/mailman/message/37042476/</ref> | ||
For the time being, we don’t (often) use OSG 3.6 - looking at the code on master (which became 3.6), there isn’t a single commit we can revert - Robert evidently did a lot of incremental improvements to the text code, adding support for other features and improving the shader support. Then at some point he collected a subset of those changes and back-ported them to 3.4 branch, which is what we revert in the commit on my fork on GitHub. | For the time being, we don’t (often) use OSG 3.6 - looking at the code on master (which became 3.6), there isn’t a single commit we can revert - Robert evidently did a lot of incremental improvements to the text code, adding support for other features and improving the shader support. Then at some point he collected a subset of those changes and back-ported them to 3.4 branch, which is what we revert in the commit on my fork on GitHub. | ||
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(The text animation assumes that setting all of emissive/ambient/diffuse/specular works on an osgText, and it no longer does - for some cases we could map the emissive color to the text color, but this would break some other cases…. and text still won’t receive normal lighting in that case)<ref>https://sourceforge.net/p/flightgear/mailman/message/36703340/</ref> | (The text animation assumes that setting all of emissive/ambient/diffuse/specular works on an osgText, and it no longer does - for some cases we could map the emissive color to the text color, but this would break some other cases…. and text still won’t receive normal lighting in that case)<ref>https://sourceforge.net/p/flightgear/mailman/message/36703340/</ref> | ||
There are some ways to fix that, but they might break aircraft compatibility (but that is maybe inevitable for this, to some degree) | |||
The best solution we discussed so far is: render the text to a texture (using the official osgText shaders from 3.6), and then apply that texture as a decal in 3D. This would allow effects to be used, which is what we need to fix the lighting problems. (mostly…) The problem is this means defining a texture quad which is correctly positioned (in terms of Z-offset) above the panel / model the text appears on. | |||
Now, all of the above is /also/ true for osgText in 3.4.0; so the aircraft developers already configured (presumably) a position + offset which gives acceptable tradeoff of ‘appearing coplanar’ and ‘avoiding Z-fighting’. The question is whether we can mimic what old osgText did, close enough that most aircraft work unmodified. And we won’t know that until someone creates the replacement code.<ref>https://sourceforge.net/p/flightgear/mailman/message/37148949/</ref> | |||