Archive 17/01/2023.

ETC2 Texture with Urho3D

projector

Urho3D supports KTX compressed image file, I would like to ask if I can use ETC2 compressed format on ETC2 supported devices? Urho3D is currently using OpenGL ES2 for mobile platform, I’m not sure If it does affect the ETC2 compressed image format support.

jmiller

Hello,

Looking into this, it is my impression that ETC2 format requires OpenGL ES 3, which Urho does not yet support.

Reference.dox says “ETC1 (Android) and PVRTC (iOS/tvOS) compressed textures are supported through the .ktx and .pvr file formats.” and I do not see ETC2 here… https://github.com/urho3d/Urho3D/blob/master/Source/Urho3D/Resource/Decompress.cpp#L272

GLES3.1 may not be too far ahead. boberfly has mentioned a branch in the forum…

HTH

projector

Thanks for your information and good to know that there is plan for to support GLES3.1.

As far as I know ETC2 is mandatory to be supported by OpenGL ES3 devices, not sure if we still can ETC2 compressed format if we run it on OpenGL ES3 devices with OpenGL ES2 API. I hope to use ETC2 in my coming project, majority of mobile devices that released within these 2-3 years support OpenGL ES3.

The code you linked contains ETC1 and PVRTC decompress functions, isn’t the ETC/PVRTC compressed texture format should stay compressed in memory? Are those functions used fo decompress in case users run it on platforms that do not support the compressed format, for example loading PVRTC on Windows PC?

jmiller

You’re welcome!

I assume that ETC1/PVRTC/DXT textures do remain compressed in VRAM… at least, that was a primary reason to support them and I do not recall reports otherwise.

Maybe someone can elucidate, or a bit of trial or digging in source…

projector

I have just tested to load ETC2 image with Urho, it printed error “Unsupported texture format in KTX file”.

looking at image.h, looks like ETC2 compressed format is not defined

github.com

urho3d/Urho3D/blob/master/Source/Urho3D/Resource/Image.h

//
// Copyright (c) 2008-2017 the Urho3D project.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

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projector

I have tried to get opengl es extension list with Urho running in ES3 capable mobile devices, it could not find the ETC2 extension, it is pretty clearly that ETC2 is not supported in OpenGL ES2 context regardless running in OpenGL ES3 capable devices.

looks like the only option to use ETC2 is to switch to OpenGL ES3. ETC2 is the only compressed format that is widely supported nowadays by both iOS and Android devices, I hope to use it in my project.

What is the status of ES3 implementation in Urho?

Eugene

If you want to have some feature, make an issue on GitHub tracker.
Or bettter, implement it on your own and make PR.

projector

Thank you, i will check with GitHub tracker. Btw, could I know if there is anyone in the team working with ES3? I got the impression someone is working with ES3, I’m happy to help, that’s also the reason I asked about the status of ES3 implementation.