How to use QSurfaceFormat instead of QGLFormat.

lygstate · wrote on 23 Oct 2013, 07:48

"QSurfaceFormat":http://qt-project.org/doc/qt-5.1/qtgui/qsurfaceformat.html
http://qt-project.org/doc/qt-5.1/qtopengl/qglformat.html

in the document of "QSurfaceFormat::depthBufferSize()":http://qt-project.org/doc/qt-5.1/qtgui/qsurfaceformat.html#depthBufferSize
There is dead functions setDepth() and depth().
@
int QSurfaceFormat::depthBufferSize() const
Returns the depth buffer size.
See also setDepthBufferSize(), setDepth(), and depth().
@

I want to know how to setDepth in QSurfaceFormat.

ZapB · wrote on 23 Oct 2013, 10:09

@
QSurfaceFormat f;
f.setDepthBufferSize( 24 );
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Looks like the docs are out of date and contain an error. I'll fix them.

ZapB · wrote on 23 Oct 2013, 11:13

Fixed in https://codereview.qt-project.org/#change,68934 Thanks for the heads up.

lygstate · wrote on 23 Oct 2013, 11:54

[quote author="ZapB" date="1382522966"]@
QSurfaceFormat f;
f.setDepthBufferSize( 24 );
@

Looks like the docs are out of date and contain an error. I'll fix them.[/quote]

Thanks for your answer, but 24 is a magical number, where does it comes from?

indeed, I want a equivalent for
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glutInitDisplayMode(GLUT_ALPHA | GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH | GLUT_STENCIL);
@
I have a piece of opengl code(generated by SCADE, that's why I can not implement it directly in Qt) code to running under QWinodw. The problem is that it's didn't running fine, so I wanna to know what kinds of initialization and running parameters should be set.

ZapB · wrote on 23 Oct 2013, 12:25

24 is the bit depth of the depth buffer being requested, it's not a magic number.

To get the equivalent to what you want I think you need this or some variation of it:

@
QSurfaceFormat f;
f.setDepthBufferSize( 24 ); // or 16, or 32 depending on what precision you want
f.setStencilBufferSize( 8 );
@

The default should automatically include an RGBA color buffer and double buffering.

lygstate · wrote on 23 Oct 2013, 13:56

Herder, thanks a lot, how about the alphaBufferSize? I want a value for it. Indeed, I am a newbie about opengl, sorry about the naive question.

ZapB · wrote on 23 Oct 2013, 14:12

@
f.setAlphaBufferSize(8);
@

although I think that is also the default (RGBA color buffer with 8 bits per channel).

ZapB · wrote on 23 Oct 2013, 14:14

Do

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qDebug() << f;
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to check both what you request and then after the context is created to see what you actually got back:

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QSurfaceFormat actualFormat = m_context->format();
qDebug() << actualFormat;
@

lygstate · wrote on 24 Oct 2013, 05:08

Hi, Robot, thanks for your vivid answer. Now I am facing a serious problem about Qt 5.x opengl works with SCADE, when I using Qt 5.x/vs2010-x86 (QWindow/QGLWidget) to show a SCADE opengl rendering staff, it's can show it correctly, but the problem is it's flashing.
With the same copy of code running under Qt 4.8.3/vs2008-x86, it's works fine. So I am confused, and don't know if this is a bug or there is something i need to take care of. Ask for advice. Really appreciate for this.

ZapB · wrote on 24 Oct 2013, 06:57

Sorry, I have no idea without seeing some code that exhibits the problem. Can you make a small compilable example that shows the issue please?

lygstate · wrote on 24 Oct 2013, 07:20

[quote author="ZapB" date="1382597848"]Sorry, I have no idea without seeing some code that exhibits the problem. Can you make a small compilable example that shows the issue please?[/quote]

"OpenGL flashing bug":https://bugreports.qt-project.org/browse/QTBUG-34295
This is my bug report, I attached the source code that can be compiled, all the dependence are included, except it's only works with vs2008/vs2010/x86/opengl version.

ZapB · wrote on 24 Oct 2013, 14:45

OK thanks. I'll try to take a look soon.