[Bug] Artifacts after windows resize with OpenGL3Renderer

[msiedlarek]

As per Lukas'es request I'm moving the discussion from this ticket here: http://cegui.org.uk/mantis/view.php?id=1051#c1310

Now answering your question:

Do you have the same issue in regular OpenGLRenderer or only OpenGL3? What OpenGL version does your driver (fully!) support?

With this configuration OpenGLRenderer works just fine:

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    Vendor: NVIDIA Corporation
    Version: 2.1 NVIDIA-8.26.26 310.40.45f01
    Renderer: NVIDIA GeForce GT 650M OpenGL Engine
    Shaders version: 1.20

With this configuration OpenGL3Renderer has the described problem after viewport resize:

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    Vendor: NVIDIA Corporation
    Version: 4.1 NVIDIA-8.26.26 310.40.45f01
    Renderer: NVIDIA GeForce GT 650M OpenGL Engine
    Shaders version: 4.10
    OpenGL profile: core

[edit]

I can do some tinkering, so if you have an idea that you'd like to try out, just say so. I'm fairly new to CEGUI, so I don't really know where to look for this problem, considering how hard it is to debug OpenGL.

[Ident]

The artefacts are quite random. Since you said OGL works, this already limits our set of possible causes a lot. The major difference between OGL and OGL3 Renderers are the usage of FBOS and VBO/VAOs. The issue could lay there, or somewhere else, for example in more minor differences, or most annoyingly: it could simply be a driver bug!

Based on the artefacts I d assume that the issue is FBO-related. If you would be so kind you could try out the following:
Open "datafiles\layouts\GameMenu.layout"
Set all

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<Property name="AutoRenderingSurface" value="True" />

to

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<Property name="AutoRenderingSurface" value="False" />

Start the SampleBrowser again and look for a change in the Sample.

[msiedlarek]

Oh, I see I caused some confusion by using sample resources for the screenshot. The problem is occurring with CEGUI working alongside my own OpenGL 3 engine. I just checked and SampleFramework app works just fine, so now I see it's probably something stupid I do. But changing AutoRenderingSurface solved the problem, so I hope you can help me locate it.

As for my engine - I'm doing the cleanup described in CEGUI documentation before calling renderAllGUIContexts(), that is I'm unbinding 2D texture and deactivating texture/shading program. Also I turned off all the rendering in my application apart from CEGUI call, and the problem remains.

[Ident]

Oh man i was 100% sure you were using the SampleBrowser..

Also I turned off all the rendering in my application apart from CEGUI call, and the problem remains.

That doesnt make sense considering you can run the SampleBrowser without issue.

Do you use "enableExtraStateSettings ()"?

[msiedlarek]

Do you use "enableExtraStateSettings ()"?

Nope, my initialization for CEGUI looks basically like this:

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    CEGUI::System::create(                                                         
        CEGUI::OpenGL3Renderer::create(),                                         
        MyCustomResourceProvider::get()                                               
    );                                                                             
                                                                                   
    CEGUI::SchemeManager::getSingleton().createFromFile("Generic.scheme");         
    CEGUI::SchemeManager::getSingleton().createFromFile("GameMenu.scheme");       
    CEGUI::Window * const root_window = (                                         
        CEGUI::WindowManager::getSingleton().loadLayoutFromFile(                   
            "GameMenu.layout"                                                     
        )                                                                         
    );                                                                             
    CEGUI::System::getSingleton().getDefaultGUIContext().setRootWindow(           
        root_window                                                               
    );

And rendering like this:

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    oglplus::Texture::Unbind(oglplus::TextureTarget::_2D);                         
    oglplus::Texture::Active(0);                                                   
    oglplus::Program::UseNone();

    CEGUI::System::getSingleton().renderAllGUIContexts();

[Ident]

What is "oglplus"?

What happens if u never make any setting in oglplus?
What happens if u turn aforementioned setting on?

[msiedlarek]

OGLplus is just a C++ wrapper for OpenGL calls, replacing those lines with raw calls changes nothing.

[Ident]

OGLplus is just a C++ wrapper for OpenGL calls, replacing those lines with raw calls changes nothing.

Weird. I never heard of that wrapper. Does it call OpenGL only if a setting is actually changed(saving the previous state) or whats the point of it?

Did you try enableExtraStateSettings (true) for the OGL3Renderer?

[msiedlarek]

Weird. I never heard of that wrapper. Does it call OpenGL only if a setting is actually changed(saving the previous state) or whats the point of it?

I use it mainly because of object lifetime management, which I did end up writing myself for previous project, before I found OGLplus. It also makes OpenGL API typesafe, which sometimes can save your life. Check it out - it's worth it: http://oglplus.org/oglplus/html/index.h ... s_features

Did you try enableExtraStateSettings (true) for the OGL3Renderer?

I did just now and it works! So I guess I can now trace an intersection of what this setting affects and what my engine does, thanks!

[Ident]

Did you try enableExtraStateSettings (true) for the OGL3Renderer?

I did just now and it works! So I guess I can now trace an intersection of what this setting affects and what my engine does, thanks!

This basically just sets and resets certain functions that are needed to be set if you changed them. Your engine MUST have changed some settings otherwise the Samplebrowser, which doesnt use this function, would also not work.

In order to reduce such problems for future users: Could you tell us why you hadnt heard of the function or how we could have documented better that this function exists or how it can be used?
Would you expect this function to be on by default? Do you think changing it to be on by default would be good?

The only issue about the function is that it introduces a certain (often unnecessary) performance reduction which is why it was off by default. However, people could then always turn it off anyways. I guess the priority for people first is that "it works".

[msiedlarek]

Oh, so it seems I was being an idiot again. I've added enableExtraStateSettings and ran my application on modified resources with AutoRenderingSurface disabled. Now that I'm running it with original GameMenu.layout it's not working anymore. Any ideas left?

As of the enableExtraStateSettings() - I think it could be mentioned in "The Beginners Guide to Initialising CEGUI". There is already a cleanup process specified for OpenGL (glBindTexture(0), glUseProgram(0), glActiveTexture(GL_TEXTURE_0)) but no mention that more may be needed.

[Ident]

There is already a cleanup process specified for OpenGL (glBindTexture(0), glUseProgram(0), glActiveTexture(GL_TEXTURE_0)) but no mention that more may be needed.

That's what the enableExtraAttribs function does for you.

Any ideas left?

bind the framebuffer to 0 before rendering. Also make 1000% sure that your library does not set any stuff at all.

Also I want to mention I once had a similar issue (also framebuffer resize related although my artefacts looked different) when using openglut or freeglut (dont remember which one, i abandoned all *glut libraries afterwards), which disappeared once i changed to glew and glfw. It could be the library you use that causes the issue. Remember that the Samplebrowser works. Wait, it does, right? If it does, including resizes, I would go and blame that library, tbh.

[msiedlarek]

There is already a cleanup process specified for OpenGL (glBindTexture(0), glUseProgram(0), glActiveTexture(GL_TEXTURE_0)) but no mention that more may be needed.

That's what the enableExtraAttribs function does for you.

And I'm just saying it should be mentioned in the guide. You asked me why I didn't know about it - it's because as a beginner I was going with the beginner guide.

bind the framebuffer to 0 before rendering. Also make 1000% sure that your library does not set any stuff at all.

Also I want to mention I once had a similar issue (also framebuffer resize related although my artefacts looked different) when using openglut or freeglut (dont remember which one, i abandoned all *glut libraries afterwards), which disappeared once i changed to glew and glfw. It could be the library you use that causes the issue. Remember that the Samplebrowser works. Wait, it does, right? If it does, including resizes, I would go and blame that library, tbh.

I tried setting both read and draw framebuffers to 0 and it didn't help. As for possible interference from my engine or OGLplus I managed to extract a minimal program that still has this issue:

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#include <SDL2/SDL.h>
#include <SDL2/SDL_video.h>

#include <CEGUI/System.h>
#include <CEGUI/RendererModules/OpenGL/GL3Renderer.h>
#include <CEGUI/SchemeManager.h>
#include <CEGUI/WindowManager.h>
#include <CEGUI/GUIContext.h>
#include <CEGUI/DefaultResourceProvider.h>
#include <CEGUI/Font.h>
#include <CEGUI/Scheme.h>
#include <CEGUI/WindowManager.h>
#include <CEGUI/falagard/WidgetLookManager.h>
#include <CEGUI/ImageManager.h>

int main()
{
    SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
    SDL_GL_SetAttribute(
        SDL_GL_CONTEXT_PROFILE_MASK,
        SDL_GL_CONTEXT_PROFILE_CORE
    );

    SDL_Window * const window = SDL_CreateWindow(
        "Sample",
        SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED,
        1200,
        700,
        SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE
    );
    SDL_GLContext sdl_opengl_context = SDL_GL_CreateContext(window);

    CEGUI::OpenGL3Renderer::bootstrapSystem();
    CEGUI::System & system = CEGUI::System::getSingleton();

    {
        CEGUI::DefaultResourceProvider * rp = (
            static_cast<CEGUI::DefaultResourceProvider*>(
                system.getResourceProvider()
            )
        );
        rp->setResourceGroupDirectory("schemes", "./datafiles/schemes/");
        rp->setResourceGroupDirectory("imagesets", "./datafiles/imagesets/");
        rp->setResourceGroupDirectory("fonts", "./datafiles/fonts/");
        rp->setResourceGroupDirectory("layouts", "./datafiles/layouts/");
        rp->setResourceGroupDirectory("looknfeels", "./datafiles/looknfeel/");

        CEGUI::ImageManager::setImagesetDefaultResourceGroup("imagesets");
        CEGUI::Font::setDefaultResourceGroup("fonts");
        CEGUI::Scheme::setDefaultResourceGroup("schemes");
        CEGUI::WidgetLookManager::setDefaultResourceGroup("looknfeels");
        CEGUI::WindowManager::setDefaultResourceGroup("layouts");
    }

    {
        CEGUI::SchemeManager::getSingleton().createFromFile("Generic.scheme");
        CEGUI::SchemeManager::getSingleton().createFromFile("GameMenu.scheme");
        CEGUI::Window * const root_window = (
            CEGUI::WindowManager::getSingleton().loadLayoutFromFile(
                "GameMenu.layout"
            )
        );
        system.getDefaultGUIContext().setRootWindow(root_window);
    }

    while (!SDL_QuitRequested()) {
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_WINDOWEVENT
                    && event.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
                int x, y;
                SDL_GL_GetDrawableSize(window, &x, &y);
                system.notifyDisplaySizeChanged({
                    static_cast<float>(x),
                    static_cast<float>(y)
                });
            }
        }

        system.renderAllGUIContexts();
        SDL_GL_SwapWindow(window);
    }

    CEGUI::OpenGL3Renderer::destroySystem();
    SDL_GL_DeleteContext(sdl_opengl_context);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}


edit

So this may be something specific about how SDL2 creates an OpenGL context? I'll look into that. All ideas still welcome.

[Ident]

Okay so you use SDL in both cases, whereas both dont work? You see, you never explicitly mentioned that you use SDL - that would have been kinda important to know, in case I knew something in that regards( I actually dont). Admittedly, I also didnt ask for it

Also: Can you please confirm that the SampleBrowser, when you click on the samples for fullscreen view, and resize the application window, still works normally? If it is, I assume we can both do a safe bet on that SDL does something wrong here.

[msiedlarek]

Also: Can you please confirm that the SampleBrowser, when you click on the samples for fullscreen view, and resize the application window, still works normally?

It does.