Cutexture: Qt UIs in Ogre

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advancingu
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Cutexture: Qt UIs in Ogre

Post by advancingu » Thu Nov 11, 2010 2:16 am

Hi,

Please allow me a shameless (but hopefully useful) plug for a new framework called Cutexture which integrates Qt User Interfaces into Ogre. Compared to previous Qt integrations for Ogre, one of its primary features is that it does not rely on widget overlays but instead renders Qt widgets into textures. If you're interested, read more here.

Cutexture is open source so please leave feedback or post patches on Github.

Thanks!
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Assaf Raman
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Re: Cutexture: Qt UIs in Ogre

Post by Assaf Raman » Thu Nov 11, 2010 5:00 pm

Nice work.
I had a look at your code, what you basically do is render QT into an image then update that image into an OGRE texture.
From the code I see you render a 32 bit qt image - meaning it has an alpha channel and transparency - am I right?

The biggest downside I see for your solution is that you need to constantly update a texture buffer, so this update can become a rendering bottleneck.

I am wandering - won't it be more efficient to render using QPaintEngine::OpenGL directly to a texture? This way all the updates will be done on the GPU side.
I am not an export on QT - so forgive me if this doesn't make sense.
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Assaf Raman
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Re: Cutexture: Qt UIs in Ogre

Post by Assaf Raman » Thu Nov 11, 2010 6:24 pm

I think it can be done, your starting point in the QT source is this directory: qt-everywhere-opensource-src-4.7.1\src\opengl

There are two main ways to go about this the "right way" as far as I can see:
1. An OpenGL only solution - meaning adding an option for the OpenGL QT renderer to get an external context (from OGRE) and then using the existing code to render to texture. You can do the same for GL ES 1 and 2 if you are interested in mobile platforms.
2. Implement a new QPaintEngine::OGRE, longer way to go - but with this method you will not be limited to OpenGL, meaning you can render QT on DX, you will only need to maintain one code base for all the render platforms (dx, gl, gles 1,2) and the code will less of a "hack".

The files you should start from if you are interested in GL are:
qt-everywhere-opensource-src-4.7.1\src\opengl\qpaintengine_opengl.cpp
qt-everywhere-opensource-src-4.7.1\src\opengl\qglpixelbuffer_win.cpp

All the GL shaders are in this file (158 fragment programs):
qt-everywhere-opensource-src-4.7.1\src\opengl\util\fragmentprograms_p.h
and sadly as assembler programs (meaning a hard time converting them back to CG\HLSL\GLSL)
You can also have a look at this file:
qt-everywhere-opensource-src-4.7.1\src\opengl\gl2paintengineex\qglengineshadersource_p.h
It contains the GL ES 2.0 shaders, because GL ES 2 supports only GLSL (and not assembly shaders) - the shaders are much more readable, but note this remark at the end:

Code: Select all

/*
    Left to implement:
        RgbMaskFragmentShader,
        RgbMaskWithGammaFragmentShader,

        MultiplyCompositionModeFragmentShader,
        ScreenCompositionModeFragmentShader,
        OverlayCompositionModeFragmentShader,
        DarkenCompositionModeFragmentShader,
        LightenCompositionModeFragmentShader,
        ColorDodgeCompositionModeFragmentShader,
        ColorBurnCompositionModeFragmentShader,
        HardLightCompositionModeFragmentShader,
        SoftLightCompositionModeFragmentShader,
        DifferenceCompositionModeFragmentShader,
        ExclusionCompositionModeFragmentShader,
*/ 
Meaning GL ES is not finished...

What do you think?
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Assaf Raman
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Re: Cutexture: Qt UIs in Ogre

Post by Assaf Raman » Thu Nov 11, 2010 6:31 pm

After looking more into the code, I see that all the GL GLSL shaders are in this directory: qt-everywhere-opensource-src-4.7.1\src\opengl\util
meaning the GL to OGRE port may be more simple the I wrote in my last post.
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Re: Cutexture: Qt UIs in Ogre

Post by madmarx » Thu Nov 11, 2010 7:36 pm

alpha channel and transparency - am I right?
I don't know this CutTexture, but I did the same : rendering the qwidget (or parts of it, or qgraphics things) into an image is very easy, and you got transparency. You just need to fill your image with 0 at the beginning.

The good part of it is that it is damn easy to do (at least for one widget), comparing to the other solutions.
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Re: Cutexture: Qt UIs in Ogre

Post by Assaf Raman » Fri Nov 12, 2010 12:43 pm

From looking more at the QT code, an option to have a native OGRE renderer for QT can be created without compiling all of QT.
QT has a plugin system. In order to have a native OGRE QT renderer - you needed to inherit QGraphicsSystem, name it QOgreGraphicsSystem, implement, then run QT with this new plug-in (look for "graphicssystem" in qt-everywhere-opensource-src-4.7.1\src\gui\kernel\qapplication.cpp for more info).

I am becoming sure that this is technically possible, it is a sort of a classic GL to OGRE port work.
The benefits of such can help both projects, QT will get the option to render with all OGRE render systems, and OGRE will get an option to have great native high performance GUI.

The biggest downside I see now for using QT is that it uses LGPL license - meaning QT can never be used on the iPhone or platforms, I don't see on the QT site even an option to pay for the right to use it on the iPhone.
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Re: Cutexture: Qt UIs in Ogre

Post by madmarx » Fri Nov 12, 2010 1:28 pm

Concerning qt/iphone, this is what I understood :

Qt is a nokia's product (cell phones etc...).
Iphone is an Apple's product.

For that reason, Qt has obviously no intention of supporting the iphone openly. There are dissident projects on the web for qt iphone, but even if you provide a perfect qt-iphone implementation, it is likely to be refused for qt trunk integration.

Qt cross platform? Not exactly the same meaning, as what I consider cross platform.
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Fri Nov 12, 2010 1:36 pm

Hi all,
thanks for the replies.

@Assaf
The image rendered has 32bits, so you have full alpha channel support. You are correct that updating a texture buffer can become a bottleneck, therefore the texture is only updated if there was a change in the UI (e.g. moving the mouse over a non-changing area causes no update). If you have non-animated UIs, I believe this should be fast enough. If someone has a better way to get Qt into Ogre, I'd be happy to hear it. However, if I understand it correctly, writing a QGraphicsSystem extension which integrates Ogre into Qt (the other way round than Cutexture) would remove the ability to have Qt output applied as a texture to objects but with the advantage of having faster performance.

@madmarx
I don't think Nokia would openly oppose iPhone development since if you write for Qt (even when targeting Qt on the iPhone), you would at the same time be writing something that could easily be released on a Nokia device as well. I would bet you will face more problems releasing a Qt app on the Apple AppStore because of their restriction on the tools you may use.
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Sat Jan 08, 2011 7:17 pm

I just came by http://www.ogre3d.org/tikiwiki/List+Of+Libraries while searching for a library. Does anyone want to add Cutexture there under the GUI section? It might be helpful for people looking for another Ogre GUI alternative.
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advancingu
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Mon Feb 21, 2011 4:58 am

Just an update that Cutexture is now a library. I refactored the code and split the game-specific code into a separate example. Hopefully this makes is more useful for others. I'll add more documentation over the next days to describe how to use it in other projects. Should be relatively straightforward though even without specific documentation as the library just consists of two classes that developers need to interact with.
Get the code on Github or watch a short video of Cutexture in action on my blog.
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Re: Cutexture: Qt UIs in Ogre

Post by texel » Fri Feb 25, 2011 4:28 pm

It could be great to be able to render QT GUI into texture (which can be applied to a mesh) and use it like scaleform.
QT has a web browser and QT Quick seems to be able to create interesting things similar to Flash.
I hope you will continue and share your work !
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advancingu
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Sat Feb 26, 2011 3:43 am

Hi Texel, Thanks for your feedback.

In the latest version you should already be able to render Qt widgets into any Ogre texture, so if you want to have e.g. Google or Facebook pages showing on the surface of any object in your 3D application/game, that should be no problem. QML should also be possible already if you use a QDeclarativeView as a widget.

Let me know if something doesn't work for you and I'll look into it.
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Re: Cutexture: Qt UIs in Ogre

Post by kineticmove » Thu Mar 24, 2011 11:51 pm

for me the good way is to provide an ogre3D backend to scenegraph (the coming new Qt backend for Qml) : see here :
http://labs.qt.nokia.com/2011/03/22/the ... ene-graph/

If we have the way to render (with full acceleration ... not cpu rendering qt widget, copy to image, then copy to buffer) a qml scene in an ogre3D texture ... it will rocks :) ... easy UI and good look, possibility to embed any 2D qml contents has a texture on Ogre3D....
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Re: Cutexture: Qt UIs in Ogre

Post by Marseyeah » Wed Apr 20, 2011 12:21 pm

I did some experimentation on integrating Ogre with the QML Scene Graph
The repository is here: https://qt.gitorious.org/qt-labs/qmlogre
To compile the project:
- first you need to pull and compile Qt from the qml-team/qtquick2 branch of http://qt.gitorious.org/+qt-developers/qt/staging/
- set the OGRE_HOME environment variable
- qmake && make

What it does is that it renders Ogre in a framebuffer object then render the texture with the rest of the QML scene. No intermediate Image, no texture upload, the whole thing should be fast.

EDIT: I only tried on Linux, I don't know if it works on Windows or Mac.
EDIT2: I fixed the build on Windows and it also works fine on this platform.
Last edited by Marseyeah on Mon May 02, 2011 4:02 pm, edited 1 time in total.
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Re: Cutexture: Qt UIs in Ogre

Post by Marseyeah » Mon May 02, 2011 2:48 pm

Here's a video of it working on Linux:
http://www.youtube.com/watch?v=b_3xfFuwGOQ
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Speculi
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Re: Cutexture: Qt UIs in Ogre

Post by Speculi » Sat Jun 11, 2011 2:53 pm

This looks very cool. Will it have a noticeable impact on performance? Is Qt able to create "real" fullscreen applications? I'm currently starting to learn some QML-stuff and I think there would be some nice possibilities with QML to create an userinterface for some little Ogre-project I want work on.
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Re: Cutexture: Qt UIs in Ogre

Post by shartte » Mon Jun 13, 2011 3:04 am

Speculi wrote:This looks very cool. Will it have a noticeable impact on performance? Is Qt able to create "real" fullscreen applications? I'm currently starting to learn some QML-stuff and I think there would be some nice possibilities with QML to create an userinterface for some little Ogre-project I want work on.
I am not sure about the performance impact of rendering the Ogre scene into a FBO. While the current repository won't be able to use "real" full screen mode, in one of the blog posts a Qt developer stated that the new scene graph implementation will simply use native OpenGL drawing calls and draw basically into anything as long as an OpenGL context is given (it shouldn't care where that comes from). The whole thing still seems to be in development, but if I understood the blog post about Qt5/lighthouse correctly, the entire QWidget stack won't be necessary to use QML/SceneGraph. This means: You get QML with native OpenGL2 rendering (no wrapper). While the current version still forces you to use a QGLWidget, that should be remedied until the end of 2011, when beta quality code for Qt5 should become available (according to their roadmap).

I guess the steps you would still need to perform (or rather, any interation layer would need to perform) are:
  • Setting up Qt/SceneGraph to use the OpenGL context it should render in.
  • Disabling the threaded renderer would be required I guess.
  • Set the viewport size for the scene graph.
  • Translate and push user input events into QApplication (since the root window isn't owned by Qt)
  • When the user interface should be drawn (callback function from the main rendering loop), process queued QApplication events, then call the paintEvent method for QSGView directly.
Right now, the issue with QSGView in its current state (alpha or pre-alpha i guess) is, that it automatically context-switches to its own GL context and swaps buffers when it's done. I guess this still has to change, along with its ties into the "old" QWidget system.

I really hope these issues are resolved on the Qt side and I will try to make the Game UI use case known to the Qt developers. While it's certainly nice to embed Ogre into QML, I guess the more interesting (and serious) use case would be embedding QML into Ogre. In my personal opinion, there's no really good (& free) alternative to Scaleform right now. QML would be a great contender for this.

Regards,
Sebastian

ps: Please vote for the feature request that would allow the QML scene to be render into an FBO.
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Sun Mar 31, 2013 5:02 am

Digging this thread out again with a brief update: I've modified the qmlogre example that was created by Nokia to build with the latest Qt 5.0.1 without using private Qt headers. Essentially this code has Ogre render into an FBO which is then integrated into a QML scene as a textured item. In other words, Qt manages the visible window as well as events and it is Ogre that renders into a texture. More infos on my blog at AdvancingUsability.
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Re: Cutexture: Qt UIs in Ogre

Post by crashtua » Sat May 11, 2013 10:31 am

Hello. I have compiled Cutexture with Ogre 1.8.2 and Qt 4.8.4. With OpenGL renderer all OK, controls shows perfectly. But on DirectX i have blured image(see attachment). Where problem can be?
sadly.png
sadly.png (12.3 KiB) Viewed 5915 times
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Re: Cutexture: Qt UIs in Ogre

Post by crashtua » Sat May 18, 2013 5:43 pm

We need change Rectangle2D position to manage texel-to-pixel mapping in DirectX to solve problem in previous post. I used such code:

Code: Select all

        Ogre::RenderSystem* rs = Ogre::Root::getSingleton().getRenderSystem();
        const Ogre::Viewport* vp = ViewManager::getSingletonPtr()->getPrimaryViewport();
        Ogre::Real hOffset = rs->getHorizontalTexelOffset() / (0.5 * vp->getActualWidth());
        Ogre::Real vOffset = rs->getVerticalTexelOffset() / (0.5 * vp->getActualHeight());
		Ogre::Rectangle2D *miniScreen = new Ogre::Rectangle2D(true);
        miniScreen->setCorners(-1.0 + hOffset, 1.0 - vOffset, 1.0 + hOffset, -1.0 - vOffset);
		miniScreen->setBoundingBox(Ogre::AxisAlignedBox(-100000.0 * Ogre::Vector3::UNIT_SCALE,
				100000.0 * Ogre::Vector3::UNIT_SCALE));
		miniScreen->setRenderQueueGroup(Ogre::RENDER_QUEUE_OVERLAY);
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Re: Cutexture: Qt UIs in Ogre

Post by rndbit » Sun Aug 04, 2013 5:53 pm

i suppose good stuff like context menus wont work with this right?
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advancingu
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Re: Cutexture: Qt UIs in Ogre

Post by advancingu » Tue Aug 13, 2013 4:40 pm

rndbit wrote:i suppose good stuff like context menus wont work with this right?
Check my new project QmlOgre for a more flexible way to integrate Ogre and Qt. Anything you can do with QML is possible there in terms of UI.
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Re: Cutexture: Qt UIs in Ogre

Post by rndbit » Mon Aug 19, 2013 4:03 pm

advancingu wrote:
rndbit wrote:i suppose good stuff like context menus wont work with this right?
Check my new project QmlOgre for a more flexible way to integrate Ogre and Qt. Anything you can do with QML is possible there in terms of UI.
i saw it but i stepped back due to very same reason - doubt that menus will work. do they? what about full screen mode? does it work too? seems like qt owns the world there..
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