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OpenGL Large triangle/ slow fillrate?

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Hiya, I have an opengl program rendering 800 or so particles with alpha blending. The particles are actually small triangles, the texture is rendered within and clamped so that the corners are not shown (if that doesnt make sense don't worry). Basically i am rendering a ton of triangles and if the triangles are about .1 by .1 by .1 in size the framerate is wonderful, about 100-150. If they are enlarged (for smoke, fire etc) or if you are very very close to them so it fills a lot of the screen the framerate drops down to around 30 fps. I have tried turning off blending as well as textures and those both dont change anything performance wise (or at least nothing noticable). Also i'm in read-only mode for the z buffer I think its just the fill rate for the polygons, how can i fix this? Could it be i'm in some wierd rendering mode? Thanks

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its normal behaviour
use lower quality textures eg tex compression etc or dont draw the particles if they get above a certain size

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Again, even without any texturing at all, just white triangles, its slow.

Is opengl really that slow to fill triangles? is there a way to fix this?

as for sorting the polygons, it shouldnt really matter, if it never writes to the z buffer. Its just adding color to the screen

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Quote:
Original post by Pirosan
Again, even without any texturing at all, just white triangles, its slow.

Is opengl really that slow to fill triangles? is there a way to fix this?

No, your video card really is that slow. OpenGL doesn't have much to do with it.

As to actually being helpful, how about posting some code? I can't imagine that you'd be drawing a particle system with glBegin/End but how are we to know?

Typically, the root problem is overdraw. When you get close to the particle system and a single particle is near screen-size, rasterizing the screen 800 times (for each particle) is just too much for any vid card. Try using LOD for the system, draw less particles as the camera approaches for any system that uses unusually large particles.

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I do use glBegin and glEnd to render my triangles as particles.

My basic code is as follows... i set up the correct modes and calculate the theta (the direction this particular set of polygons is pointing. i do this once per bunch, i'm not expecting a certain set of particles to fly too far apart) in BillboardBegin:


cameraLocation[0] = camX;

cameraLocation[1] = camY;

cameraLocation[2] = camZ;



objectCenter[0] = objPosX;

objectCenter[1] = objPosY;

objectCenter[2] = objPosZ;

float[] distObject = new float[]{(camX - objPosX),(camY - objPosY), (camZ- objPosZ)};



GL11.glDisable(GL11.GL_LIGHTING);

GL11.glEnable(GL11.GL_BLEND);

GL11.glBlendFunc (GL11.GL_SRC_ALPHA, GL11.GL_ONE);



GL11.glDepthMask(false);





theta = (float) Math.atan(distObject[2] / distObject[0]);

System.out.println("the answer is:" + theta);



currCos = (float)(-theta * 180 / 3.14) + 90;

GL11.glTexParameterf(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_S, GL11.GL_CLAMP);

GL11.glTexParameterf(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_WRAP_T, GL11.GL_CLAMP);



I render the polygons in DrawBillboard. I have a function which accesses an array of positions and sizes, it calls this method for each particle that is drawn:


GL11.glPushMatrix();

GL11.glTranslatef(p.x, p.y, p.z);

GL11.glRotatef(currCos,0f,1f,0f);


GL11.glBegin(GL11.GL_TRIANGLE_STRIP);


GL11.glTexCoord2f(-.5f,0);

GL11.glColor4f(p.color.r,p.color.g,p.color.b,p.color.a);

GL11.glVertex3f(-1.5f*p.size,-.5f*p.size,0);



GL11.glTexCoord2f(1.5f,0);

GL11.glVertex3f(1.5f*p.size,-.5f*p.size,0);

GL11.glTexCoord2f(0.5f,2);

GL11.glVertex3f(0*p.size,1.5f*p.size,0);


GL11.glEnd();
GL11.glPopMatrix();


You can sumise what i put for BillboardEnd, basically setting lighting to true, blending to false and so on.

Please be aware this is not C++, so the equasions and/or methods may look slightly different. this is Java, but it handles opengl the same way. I know i have done my calculations correctly, don't worry about that

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maybe this is stupid suggestion. but your debug print code could be really slow if it's put in the wrong place.

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not a stupid suggestion at all, thanks im sure that will speed something up :)

but it still slows down, is there a way to better optimize, or perhalps set in a more hardware rendering mode?

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You simply can't draw a ton of huge triangles, create an insane amount of overdraw and waste a ton of fillrate and just expect there to be magical switch to make it go fast. That's like asking for the magical words to make a cripple win olympic gold for 100m. If you can't find a way to prevent each pixel being set a few dozen times that's pretty much it. You can try using your own minimalistic fragment shader, but beyond that there simply is no glQuadrupleFillrate(GL_TRUE) function.

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That responce really didnt get me anywhere, i was being serious. I understand what you are saying, there is no fix it function or mode, i was just fishing around for advice. I don't know if opengl is taking full advantage of my graphics card or not.

In direct X there is a way to set rendering to software or hardware, is there one in opengl?

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The only way I know of would be either deinstalling the graphic card drivers (or installing those that came with Windows) or deliberately using a pixel format that isn't supported.

There was also something you can try. Use shaders or programs and let the fragment shader/program do nothing but output a constant color. That will pretty much tell you your upper limit.

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If you want to reduce fill you could use quads like everyone else does. In fact, I think that should cut it in half, and one more vertex per particle isn't the end of the world.

EDIT: And if your using glBegin and fillrate limited then you certainly aren't near the limit when it comes to vertices.

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Quote:
Original post by RAZORUNREAL
If you want to reduce fill you could use quads like everyone else does. In fact, I think that should cut it in half, and one more vertex per particle isn't the end of the world.


erm, why would sending quads help?
he is still going to be filling the same screen space...

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Hmmm, the biggest problem you can have with a particle system is fill-rate, if the system is to close to the camera you have massive fill-rate issues, you can see this even in big titles some times. As for things I see you can improve to just help with general performance.

For best performance you should use Varrays, or at least stop calling glbegin/glend for every single particle/poly, that can really hurt performance.

Also are you calling your gltexParameter every frame? Those are applied to textures, once done; you don’t have to keep doing them. So just do that when you load the texture, I might have misunderstood?

While on the note, if you are changing state on every polygon this can also cause slow downs

The most ideal way to do things would be to setup all states, create all geometry(given that its dynamic), give opengl all the geometry, and then move on, that way you spend the least amount of time on the transfer to opengl.

If you had static geometry you would want to move the create geometry to your loading routines.

Maybe that helped some.

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Whats your z buffer set to? If its off I suppose its concievable that each triangle it filling the screen. Having it set to only draw triangles that are greater than whats in the zbuffer might help.

Jason

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Quote:
Original post by phantom
erm, why would sending quads help?
he is still going to be filling the same screen space...


Well, he said the particles are small triangles, so assuming he is using "round" particles and draws them on triangles, then quads would be a better fit and waste less fillrate. If my naive drawing of a sphere in a triangle and a square isn't too far off, then he is right about a triangle filling twice the area and wasting twice as much fillrate (without alpha testing, of which I hope it would at least terminate a bit earlier). I suddenly remembered another opportunity of someone using single triangles, thinking it would be very clever as it's using only half as many triangles, ignoring that polycount is the lesser problem and his "solution" to a non-existant problem just made the actual problem twice as bad.

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Even I think the problem is with the fill rate. The rasterization process is taking too much time to redraw the particles at a bigger size compared to a smaller size. It makes logical sense when you have a low performance graphics card. The speed of the rasterization process totally depends on your graphics card. By what you are saying, if just increasing the size of the polygon is making an performance drop, then it could be a slow graphics card issue.

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Thank you very much for your help. I changed to quads and at 4000 (semi large particles) speed increased by 15 frames per second. Also, this graphics card is relatively bad ^_^; so i can understand it having troubles with the fill rate, ill try it on my 6600 and see what happens!

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      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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
    • By reenigne
      For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
      I also run grhmedia.com where I host the projects and code for the tutorials I have online.
      Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

      Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
      Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

      At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon. 

      I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time. 
      I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

      I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
      I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
      I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
      Maybe another fee if it is related but not directly in the content. 
      The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

      So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
      Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

      I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos. 
    • 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
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