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OpenGL OpenGL vs Monitor Refresh Rates

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As I type this I''m happily in 1024x764x32, running at 85hz. When run my opengl apps in fullscreen, i''m still in 1024x764x32, but i''m running at 60hz. My own demos, quake 3, someone else''s demos, everything. anyone care to explain?

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Guest Anonymous Poster
You must be using Windows XP? download SP1 and your problem is gone for good

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nope, 2000. it''s always done it (yes, i have the latest drivers).

it''s a geforce ti 4200 if it helps...

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its bcuz the damn f***ing detonator drivers use a default refreshrate of 60hz (in newer versions u can set them 4 directx but not 4 opengl)... but u can use tools like powerstrip (not free) to set refreshrates 4 each resolution independent if u use opengl or directx...

there was also a tool called hzres or similar, but u should NOT use it if u dont know what ur doing (otherwise ur monitor will visit a service center :D)


T2k

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hey, i found i really good program called ReForce which sets all default refresh rates to the highest ones the monitor can handle and it works fine.

damn, i thought that problem only existed on windows xp.

*sniff* there goes my last reason by being crap at quake 3 :''(

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what are you yapping about?

When you change the displaysettings you can set the freq as well, and if you enumrate the displaymodes and the user is smart enough to NOT uncheck the ''hide modes that the monitor cannot display'' then you only get valid freq modes..

and if you like, you can let the user choose the mode from the list of modes you get when you enumrate..

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Mazy

under windows 2000 the refresh rate will always go to 60hz when switching to fullscreen OpenGL or DirectX. This was because the "Always use best option" was removed from the frequency settings, meaning that EVERY directx or ogl app going into fullscreen was forced to use 60hz.

if you read carefully i did say that this was when i was running fullscreen opengl apps...

besides, since when could you enumerate anything with opengl?

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quote:
Original post by MENTAL
besides, since when could you enumerate anything with opengl?


You don''t enumerate with OpenGL. You use the Win32 API call EnumDisplaySettings(). Once you''ve obtained the settings you want, you pass them to ChangeDisplaySettings(). One of the members of the DEVMODE structure is dmDisplayFrequency...

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We covered this subject a while back in this thread http://www.gamedev.net/community/forums/topic.asp?topic_id=163391

Towards the bottom you''ll find code snippets from myself and someone else outlineing the changes that have to be made to the dmScreenSettings structure used to switch teh display to full screen mode (pay attension to teh flags used)

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Mental : in opengl you dont have a fullscreen option, you just set the resolution with win32 commands and make a borederless maximized window, so therefore you cannot blame the drivers opengl ''fullscreen mode''

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So the problem may come from Glut ? I use glut for creating the window and i let him manage all that stuff. To switch to full screen i use a glut function (glutFullScreen) , and may be this function sets a default refresh rate of 60 Hz ?

Although, there is still the problem of frame rate drop down from 60FPS to 30FPS ... Have to do with vsync i guess, but even NVRefresh didn''t solve my problem .

No one here use glut and can tell me his experience ?

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quote:
Original post by MazyNoc
Mental : in opengl you dont have a fullscreen option, you just set the resolution with win32 commands and make a borederless maximized window, so therefore you cannot blame the drivers opengl ''fullscreen mode''



From MSDN ChangeDisplaySettings


dwflags
[in] Indicates how the graphics mode should be changed. This parameter can be one of the following values.
...
CDS_FULLSCREEN
...

This looks like an explicit notification that we''d like fullscreen mode.

And given that the caller has to explicitly specify use my frequency by setting the DM_DISPLAYFREQUENCY flag in DEVMODE.dmFields, not setting it implies that Windows and/or the display driver should choose a value. So when Windows and/or the driver is given the opportunity to choose a refresh rate and it chooses 60Hz I feel justified in calling that poor, broken behavior that should be fixed. The fact that NVidia drivers provide a table in the driver settings for DirectX default refresh rates but not for OpenGL refresh rates shows they recognize that ppl do not expect every game to choose a refresh rate, but still refuse to do it for OpenGL.

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Well, ChangeDisplaySettings is a Win32 API function, NOT an OpenGL function. It is the OpenGL specification that (deliberately) lacks a means for setting the display mode and has nothing to do with the drivers.

The method of preparing the hardware and OS for OpenGL rendering is different for each OS. It is up to the OS to provide a means of said preparation. For Windows, that method is ChangeDisplaySettings plus the wiggle functions.

Since DirectX is platform-specific, it is able to include it''s own means of setting up the hardware. That is why nVidia provides a table in the driver settings for DirectX, but not OpenGL - OpenGL does not support such a table.

At any rate, as MazyNoc said, OpenGL does not have a fullscreen mode. CDS_FULLSCREEN is a Win32 thing, not an OpenGL thing.

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quote:
Original post by Dave Hunt
Well, ChangeDisplaySettings is a Win32 API function, NOT an OpenGL function. It is the OpenGL specification that (deliberately) lacks a means for setting the display mode and has nothing to do with the drivers.

...

Since DirectX is platform-specific, it is able to include it''s own means of setting up the hardware. That is why nVidia provides a table in the driver settings for DirectX, but not OpenGL - OpenGL does not support such a table.

At any rate, as MazyNoc said, OpenGL does not have a fullscreen mode. CDS_FULLSCREEN is a Win32 thing, not an OpenGL thing.



Fine -- lets call it a Windows Full Screen mode. 60Hz is an undesirable refresh rate for any full-screen application, whether its DirectX, OpenGL, GDI or otherwise. Regardless of that, NVidia''s display driver is responsible for all these drawing modes anyway.

NVRefreshTool manages to set default refresh rates for OpenGL modes by tweaking the NVidia drivers, so arguing about whether or not the driver is capable of doing it is pointless.

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As has been stated, ChangeDisplaySettings() CAN change the refresh rate, even with nVidia drivers. The NVRefresh tool was created to work around the issue where Windows doesn''t request the best refresh rate when changing display modes. The problem of defaulting to 60hz is actually a Windows (certain versions) problem, not a driver problem.

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Actually, on LCD displays you often have a responsetime that are around 16ms and that will max on 62.5Hz, anything faster doesnt give you anything. And when you dont have digital input to the display then the analog to digital converter is more accurate the lower the frequency you have, and since you dont get flickering in 60Hz on a regular LCD then 60Hz is the prefered speed.

So maybe the selection of 60Hz isnt a bug, its an assumption that all ppl have LCD monitors

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      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
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