• Advertisement
Sign in to follow this  

OpenGL WGL_EXT_swap_control extension present? to activate it?

This topic is 1663 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Hi,
in my multiplatform OpenGL application, i require WGL_EXT_swap_control extension capability. 
I have it running properly on Linux and MacOSX. 

In WinXP and Win7, glGetString(GL_EXTENSIONS) returns null (i still dont kwno why), so,
- how to know if WGL_EXT_swap_control extension is present?
- how to enable it?

regards
dani

Share this post


Link to post
Share on other sites
Advertisement

First, WGL extensions belongs to the WGL API, which is the Windows layer for OpenGL. Not saying that other platforms don't have an equivalent extension, but WGL_EXT_swap_control itself is necessarily Windows only.
 

Second, if glGetString returns a null pointer, then that's because you haven't created and activated a rendering context yet.

Share this post


Link to post
Share on other sites

Thank you, of course you're right.

 

- After having my context created, glGetString(GL_EXTENSIONS) returns: GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_blend_color GL_EXT_abgr GL_EXT_texture3D GL_EXT_clip_volume_hint GL_EXT_compiled_vertex_array GL_SGIS_texture_edge_clamp GL_SGIS_generate_mipmap GL_EXT_draw_range_elements GL_SGIS_texture_lod GL_EXT_rescale_normal GL_EXT_packed_pixels GL_EXT_separate_specular_color GL_ARB_multitexture GL_EXT_texture_env_combine GL_EXT_bgra GL_EXT_blend_func_separate GL_EXT_secondary_color GL_EXT_fog_coord GL_EXT_texture_env_add GL_ARB_texture_cube_map GL_ARB_transpose_matrix GL_ARB_texture_env_add GL_IBM_texture_mirrored_repeat GL_EXT_multi_draw_arrays GL_NV_blend_square GL_ARB_texture_compression GL_3DFX_texture_compression_FXT1 GL_EXT_texture_filter_anisotropic GL_ARB_texture_border_clamp GL_ARB_point_parameters GL_ARB_texture_env_combine GL_ARB_texture_env_dot3 GL_ARB_texture_env_crossbar GL_EXT_texture_compression_s3tc GL_ARB_shadow GL_ARB_window_pos GL_EXT_shadow_funcs GL_EXT_stencil_wrap GL_ARB_vertex_program GL_EXT_texture_rectangle GL_ARB_fragment_program GL_EXT_stencil_two_side GL_ATI_separate_stencil GL_ARB_vertex_buffer_object GL_EXT_texture_lod_bias GL_ARB_fragment_shader GL_ARB_shader_objects GL_ARB_shading_language_100 GL_ARB_texture_non_power_of_two GL_ARB_vertex_shader GL_NV_texgen_reflection GL_ARB_point_sprite GL_EXT_blend_equation_separate GL_ARB_depth_texture GL_ARB_texture_rectangle GL_ARB_draw_buffers GL_ARB_pixel_buffer_object GL_WIN_swap_hint GL_EXT_framebuffer_object 

--> WGL_EXT_swap_control is not found. Current OS is WinXP.

 

- I didn't want to go on and on, and i made a mistake: i require WGL_EXT_swap_control under Windows, and GLX_SGI_video_sync under Linux, because what i want to do at the end is activating synchronization for swap buffering and vertical refresh. In WinXP it doesn't work for me.

Share this post


Link to post
Share on other sites

If this is an older NVIDIA card (which it looks like from the available extensions) then you should note the text in the NVIDIA control panel advising that for GL applications you should use the control panel for selecting vsync.

 

Despite this, I have seen some more recent NVIDIA cards where using WGL_EXT_swap_control does work, but there are a few gotchas with it.

 

First one is that the driver may be automatically chopping your extensions string.  It does this for compatibility with some older games (e.g. in the Quake series) where the extensions string was copied to a fixed size buffer, causing the game to crash if the extensions string was too long.  The driver may be mis-identifying your game as one that needs this attention and you can verify if this is the case by comparing your extensions string with e.g. that from the GL extensions viewer.  Unfortunately NVIDIA have removed the capability to control this behaviour from more recent drivers, so you're stuck with it.

 

Secondly, you may be able to access the WGL extensions by calling wglGetExtensionsStringEXT.  Check that for the presence of WGL_EXT_swap_control.

 

Thirdy, it's always an option to bypass the extensions string and just call wglGetProcAddress on wglSwapIntervalEXT - if it returns non-NULL for you then you should be able to make wglSwapIntervalEXT calls even despite it not being present in the extensions string (whether or not they work is another matter).

 

It's worth noting that this is absolutely nothing to do with the OS - this is all behaviour dictated by the driver.  Yes, the driver is OS-specific, but the wacky stuff is in the driver, not the OS.

Share this post


Link to post
Share on other sites

If this is an older NVIDIA card (which it looks like from the available extensions) then you should note the text in the NVIDIA control panel advising that for GL applications you should use the control panel for selecting vsync.

 

Despite this, I have seen some more recent NVIDIA cards where using WGL_EXT_swap_control does work, but there are a few gotchas with it.

 

First one is that the driver may be automatically chopping your extensions string.  It does this for compatibility with some older games (e.g. in the Quake series) where the extensions string was copied to a fixed size buffer, causing the game to crash if the extensions string was too long.  The driver may be mis-identifying your game as one that needs this attention and you can verify if this is the case by comparing your extensions string with e.g. that from the GL extensions viewer.  Unfortunately NVIDIA have removed the capability to control this behaviour from more recent drivers, so you're stuck with it.

 

Secondly, you may be able to access the WGL extensions by calling wglGetExtensionsStringEXT.  Check that for the presence of WGL_EXT_swap_control.

 

Thirdy, it's always an option to bypass the extensions string and just call wglGetProcAddress on wglSwapIntervalEXT - if it returns non-NULL for you then you should be able to make wglSwapIntervalEXT calls even despite it not being present in the extensions string (whether or not they work is another matter).

 

It's worth noting that this is absolutely nothing to do with the OS - this is all behaviour dictated by the driver.  Yes, the driver is OS-specific, but the wacky stuff is in the driver, not the OS.

 

WGL_EXT_swap_control works with nvidia GPUs as long as the user has set v-sync to "use the application settings"(or something equivalent, varies a bit between driver versions) in the control panel, if it is set to something else (adaptive, adaptive(half refresh rate) , Off, On, etc),  WGL_EXT_swap_control is ignored. (It is possible that nvidia hides the extension if the user has forced a setting for it (I know i would do that if i was nvidia atleast to show applications that it is pointless to display that option to the end user)

Edited by SimonForsman

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Now

  • Advertisement
  • Similar Content

    • By Balma Alparisi
      i got error 1282 in my code.
      sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
      #version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
      #version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

    • By khawk
      We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
      Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

      View full story
    • By TheChubu
      The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
      SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
      OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
      GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
      GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
      The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
      Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
      GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
      Industry Support for OpenGL 4.6
      “With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
      "OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

      View full story
    • By _OskaR
      Hi,
      I have an OpenGL application but without possibility to wite own shaders.
      I need to perform small VS modification - is possible to do it in an alternative way? Do we have apps or driver modifictions which will catch the shader sent to GPU and override it?
    • By xhcao
      Does sync be needed to read texture content after access texture image in compute shader?
      My simple code is as below,
      glUseProgram(program.get());
      glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
      glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
      glDispatchCompute(1, 1, 1);
      // Does sync be needed here?
      glUseProgram(0);
      glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
      glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                     GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, texture[1], 0);
      glReadPixels(0, 0, kWidth, kHeight, GL_RED_INTEGER, GL_UNSIGNED_INT, outputValues);
       
      Compute shader is very simple, imageLoad content from texture[0], and imageStore content to texture[1]. Does need to sync after dispatchCompute?
  • Advertisement