opengl-4 | 易学教程

Can I program/compile OpenGL 4.0 code on my computer without a graphics card or MESA?

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问题 I recently began working with Open GL 4.0 using the Redbook 8th edition. From the start of the morning until now I wasn't able to compile the 'HelloWorld' of OpenGL programs. I configured the dependencies, transferred file contents of freeGlut/GLEW/GLSL to the respective VC folder for my VS 2013 C++ IDE. I eventually became convinced that the catalyst for this breakdown of events happened because VS was referencing multiple lib files in different locations and the linker couldn't make heads-

near/far planes and z in orthographic rasterization

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问题 Ive coded tons of shaders but Ive stumbled into something I never realized before. I needed a vertex + fragment shader with a simple orthographic projection, with no depth test. The camera is Z-aligned with the origin. I disabled GL_DEPTH_TEST, and masked depth writes. It was so simple infact, that I decided I didnt even need a projection matrix. In my complete ignorance and ingenuity, I thought that for any triangle vertex, the vertex shader would simply pass x,y(,z = <whatever> ,w = 1) to

Failing to map a simple unsigned byte rgb texture to a quad:

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问题 I have a very simple program that maps a dummy red texture to a quad. Here is the texture definition in C++: struct DummyRGB8Texture2d { uint8_t data[3*4]; int width; int height; }; DummyRGB8Texture2d myTexture { { 255,0,0, 255,0,0, 255,0,0, 255,0,0 }, 2u, 2u }; This is how I setup the texture: void SetupTexture() { // allocate a texture on the default texture unit (GL_TEXTURE0): GL_CHECK(glCreateTextures(GL_TEXTURE_2D, 1, &m_texture)); // allocate texture: GL_CHECK(glTextureStorage2D(m

Multi-Threaded Video Decoder Leaks Memory

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问题 My intention is to create a relatively simple video playback system to be used in a larger program that I am working on. Relevant code to the video decoder is here. The best I have been able to do so far is narrow down the memory leak to this section of code (or rather I have not noticed any memory leaks occurring when video is not used). This is probably a very broad question how ever I am unsure of the scope of the issue I am having and as such of how to word my question. What I want to

Using glBindVertexArray in update loop in DSA code or not

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问题 I'm the process of converting some opengl code to DSA and everywhere its written not to bind the vertex array, because its inherit in DSA. So I use GLuint VBO, VAO, indexBuffer; glCreateVertexArrays(1, &VAO); glCreateBuffers(1, &indexBuffer); glCreateBuffers(1, &VBO); ... instead of the glGen... counterparts. But now I just wonder whether there is a DSA version of binding the vertex arrays in the update loop. Now I have while (!glfwWindowShouldClose(window)) { glfwPollEvents(); glClearColor(0

OpenGL 4.0 GPU Draw Feature?

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问题 In Wikipedia and other sources' description of OpenGL 4.0 I read about this feature: Drawing of data generated by OpenGL or external APIs such as OpenCL, without CPU intervention. What is this referring to? Edit : Seems like this must be referring to Draw_Indirect which I believe somehow extends the draw phase to include feedback from shader programs or programs from interop (OpenCL/CUDA basically) It looks as if there are a few caveats and tricks to getting the calls to keep staying on the

How to create OpenGL 3.x or 4.x context in Ruby?

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问题 I've looked everywhere, but there seam to be no ruby binding that would allow to create OpenGL 3/4 context. It do not have to be complete OpenGL binding library, just portion that creates OpenGL context. Update: If I'm desperate enough I'll do partial glfw ruby binding with ruby ffi. So pls save me from that ;) 回答1: I have written a library that can create an OpenGL 3 or 4 context on most platforms (provided it is supported). It's called Ray. You don't have to use its drawable system or DSL,

How do I make this simple OpenGL code (works in a “lenient” 3.3 and 4.2 profile) work in a strict 3.2 and 4.2 core profile?

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问题 I had some 3D code that I noticed wouldn't render in a strict core profile but fine in a "normal" (not explicitly requested-as-core-only) profile context. To isolate the issue, I have written the smallest simplest possible OpenGL program drawing just a triangle and a rectangle: I have posted that OpenGL program as a Gist here. With the useStrictCoreProfile variable set to false, the program outputs no error messages to the console and draws a quad and a triangle as per the above screenshot,

OpenGL 4.0 GPU Draw Feature?

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In Wikipedia and other sources' description of OpenGL 4.0 I read about this feature: Drawing of data generated by OpenGL or external APIs such as OpenCL, without CPU intervention. What is this referring to? Edit : Seems like this must be referring to Draw_Indirect which I believe somehow extends the draw phase to include feedback from shader programs or programs from interop (OpenCL/CUDA basically) It looks as if there are a few caveats and tricks to getting the calls to keep staying on the GPU for any extended amount of time past the second run but it should be possible. If anyone can provide

Texture mapping using a 1d texture with OpenGL 4.x

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I want to use a 1d texture (color ramp) to texture a simple triangle. My fragment shader looks like this: #version 420 uniform sampler1D colorRamp; in float height; out vec4 FragColor; void main() { FragColor = texture(colorRamp, height).rgba; } My vertex shader looks like this: #version 420 layout(location = 0) in vec3 position; out float height; void main() { height = (position.y + 0.75f) / (2 * 0.75f); gl_Position = vec4( position, 1.0); } When drawing the triangle I proceed this way (I removed error checking form code for better readability): glUseProgram(program_); GLuint samplerLocation