FreeGLUT:

- Based on the GLUT API.
- GLUT has been around for about as long as OpenGL itself.
- Many tutorials and examples out there use GLUT.
- Takes care of implementing the event loop and works through callbacks (good for simple stuff, makes things like precisely timed animation loops and low latency input much harder though).

GLFW:

- Designed from scratch with the experiences of other frameworks in mind.
- Gives much finer control over context creation and window attributes.
- GLFW-**2** Provides basic threading support functions (thread creation, synchronization). –– removed from GLFW-3
- GLFW-**2** Provides basic image file loading support. –– removed from GLFW-3
- Gives very detailed access to input devices.
- Event loop is in control of the programmer which allows for much preciser timing and lower latency.

Each time, when I manually run `tcpdump`, I have to use &lt;kbd&gt;Ctrl&lt;/kbd&gt;+&lt;kbd&gt;C&lt;/kbd&gt; to stop it. Now I want to schedule my `tcpdump` with cronjob and I only need it to run for 1 and half hours. Without manually running &lt;kbd&gt;Ctrl&lt;/kbd&gt;+&lt;kbd&gt;C&lt;/kbd&gt; or kill command, how can it be stopped automatically? Here is the command I am testing:

    tcpdump -i eth0 &#39;port 8080&#39; -w  myfile

I can schedule another cronjob  to kill the `tcpdump` process, but it seems not a good idea. 

How to schedule tcpdump to run for a specific period of time?

In Ansible 1.7, I can use --tags from the command-line to only run a subset of that playbooks tasks. 

But I&#39;m wanting to bake into my playbook to run a set of roles with only tasks that match tags. That is, I don&#39;t want to have to pass this in via the command-line since it will be the same every time. 

At first I thought it was this command, but this does the opposite: tagging tasks with these tags instead of filtering them out based on this. 

    roles:
      - { role: webserver, port: 5000, tags: [ &#39;web&#39;, &#39;foo&#39; ] }

I can imagine implementing this using conditionals but tags would be a much more elegant way of achieving this.

Ansible: In a playbook, filter a role by tag(s) without passing at the command-line

My university started teaching a course which includes OpenGL programming. They make us use FreeGLUT to create a window and a context for OpenGL, but I found an online course at lynda.com about OpenGL in which they use GLFW instead of FreeGLUT.

So I want to know which one should I use and what are the differences between the two?

What is the difference between FreeGLUT vs GLFW?

<p>My university started teaching a course which includes OpenGL programming. They make us use FreeGLUT to create a window and a context for OpenGL, but I found an online course at lynda.com about OpenGL in which they use GLFW instead of FreeGLUT.</p>
<p>So I want to know which one should I use and what are the differences between the two?</p>


I want to know if &quot;if-statements&quot; inside shaders (vertex / fragment / pixel...) are really slowing down the shader performance. For example:

Is it better to use this:

    vec3 output;
    output = input*enable + input2*(1-enable);
instead of using this:

    vec3 output;
    if(enable == 1)
    {
        output = input;
    }
    else
    {
        output = input2;
    }

in another forum there was a talk about that (2013): http://answers.unity3d.com/questions/442688/shader-if-else-performance.html
Here the guys are saying, that the If-statements are really bad for the performance of the shader.

Also here they are talking about how much is inside the if/else statements (2012):
https://www.opengl.org/discussion_boards/showthread.php/177762-Performance-alternative-for-if-(-)

maybe the hardware or the shadercompiler are better now and they fix somehow this (maybe not existing) performance issue.

EDIT:

What is with this case, here lets say enable is a uniform variable and it is always set to 0:

    if(enable == 1) //never happens
    {
        output = vec4(0,0,0,0);
    }
    else  //always happens
    {
        output = calcPhong(normal, lightDir);
    }

I think here we have a branch inside the shader which slows the shader down. Is that correct?

Does it make more sense to make 2 different shaders like one for the else and the other for the if part?

Do conditional statements slow down shaders?

I can&#39;t get the additional libraries I am working with to link into my project properly.

I am using CLion, which uses cmake to build it&#39;s projects. I am trying to use several libraries in conjunction with OpenGL to texture some objects. I initially built it in Visual Studio, because I couldn&#39;t ever figure out how to get cmake to work with Clion. However, now that the code is all working (in Visual Studio, anyways), I want to be able to use CLion for it, because that is my preferred IDE.

I am still new to cmake, and I don&#39;t understand what I am doing wrong with my `CMakeLists.txt`. Here is what I have:

    cmake_minimum_required(VERSION 3.3)
    project(texture_mapping)
    find_package(OpenGL REQUIRED)
    link_directories(${OPENGL_gl_LIBRARY})
    
    set(CMAKE_CXX_FLAGS &quot;${CMAKE_CXX_FLAGS} -std=c++11&quot;)
    
    set(SOURCE_FILES main.cpp camera.h display.h display.cpp mesh.cpp mesh.h obj_loader.cpp obj_loader.h shader.cpp shader.h stb_image.c stb_image.h texture.cpp texture.h transform.h)
    
    link_directories(texture_mapping ${PROJECT_SOURCE_DIR}/lib)
    
    add_executable(texture_mapping ${SOURCE_FILES})
    
    target_include_directories(texture_mapping PUBLIC ${PROJECT_SOURCE_DIR}/include)
    target_link_libraries(texture_mapping SDL2 SDL2main SDL2test glew32 glew32s ${OPENGL_gl_LIBRARY})

I tweaked it until it didn&#39;t give me any more errors in CLion, but the header files are still not recognized in my code.

Here is the structure of my project:  
[![project structure][1]][1]

So, I put all of the libraries I needed, but it doesn&#39;t appear to be recognizing them in the code. Clion recognizes them in the project (they aren&#39;t appearing red with errors), but when it is built (when I attempt to run it in CLion), I get these errors:

    CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4MeshD2Ev&#39;:
    ...texture-mapping/mesh.cpp:30: undefined reference to `_imp____glewDeleteVertexArrays&#39;
    CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4Mesh8InitMeshERK12IndexedModel&#39;:
    ...texture-mapping/mesh.cpp:36: undefined reference to `_imp____glewGenVertexArrays&#39;
    ...texture-mapping/mesh.cpp:37: undefined reference to `_imp____glewBindVertexArray&#39;
    ...texture-mapping/mesh.cpp:39: undefined reference to `_imp____glewGenBuffers&#39;
    ...texture-mapping/mesh.cpp:40: undefined reference to `_imp____glewBindBuffer&#39;
    ...texture-mapping/mesh.cpp:41: undefined reference to `_imp____glewBufferData&#39;
    ...texture-mapping/mesh.cpp:43: undefined reference to `_imp____glewEnableVertexAttribArray&#39;
    ...texture-mapping/mesh.cpp:44: undefined reference to `_imp____glewVertexAttribPointer&#39;
    ...texture-mapping/mesh.cpp:46: undefined reference to `_imp____glewBindBuffer&#39;
    ...texture-mapping/mesh.cpp:47: undefined reference to `_imp____glewBufferData&#39;
    ...texture-mapping/mesh.cpp:49: undefined reference to `_imp____glewEnableVertexAttribArray&#39;
    ...texture-mapping/mesh.cpp:50: undefined reference to `_imp____glewVertexAttribPointer&#39;
    ...texture-mapping/mesh.cpp:52: undefined reference to `_imp____glewBindBuffer&#39;
    ...texture-mapping/mesh.cpp:53: undefined reference to `_imp____glewBufferData&#39;
    ...texture-mapping/mesh.cpp:55: undefined reference to `_imp____glewBindVertexArray&#39;
    ...texture-mapping/mesh.cpp:56: undefined reference to `_imp____glewBindVertexArray&#39;
    CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4Mesh4DrawEv&#39;:
    ...texture-mapping/mesh.cpp:61: undefined reference to `_imp____glewBindVertexArray&#39;
    ...texture-mapping/mesh.cpp:65: undefined reference to `_imp____glewBindVertexArray&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6ShaderC2ERKSs&#39;:
    ...texture-mapping/shader.cpp:5: undefined reference to `_imp____glewCreateProgram&#39;
    ...texture-mapping/shader.cpp:11: undefined reference to `_imp____glewAttachShader&#39;
    ...texture-mapping/shader.cpp:14: undefined reference to `_imp____glewBindAttribLocation&#39;
    ...texture-mapping/shader.cpp:15: undefined reference to `_imp____glewBindAttribLocation&#39;
    ...texture-mapping/shader.cpp:17: undefined reference to `_imp____glewLinkProgram&#39;
    ...texture-mapping/shader.cpp:20: undefined reference to `_imp____glewValidateProgram&#39;
    ...texture-mapping/shader.cpp:23: undefined reference to `_imp____glewGetUniformLocation&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader4BindEv&#39;:
    ...texture-mapping/shader.cpp:28: undefined reference to `_imp____glewUseProgram&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader6UpdateERK9TransformRK6Camera&#39;:
    ...texture-mapping/shader.cpp:35: undefined reference to `_imp____glewUniformMatrix4fv&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6ShaderD2Ev&#39;:
    ...texture-mapping/shader.cpp:42: undefined reference to `_imp____glewDetachShader&#39;
    ...texture-mapping/shader.cpp:43: undefined reference to `_imp____glewDeleteShader&#39;
    ...texture-mapping/shader.cpp:46: undefined reference to `_imp____glewDeleteProgram&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader16CheckShaderErrorEjjbRKSs&#39;:
    ...texture-mapping/shader.cpp:79: undefined reference to `_imp____glewGetProgramiv&#39;
    ...texture-mapping/shader.cpp:81: undefined reference to `_imp____glewGetShaderiv&#39;
    ...texture-mapping/shader.cpp:86: undefined reference to `_imp____glewGetProgramInfoLog&#39;
    ...texture-mapping/shader.cpp:88: undefined reference to `_imp____glewGetShaderInfoLog&#39;
    CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader12CreateShaderERKSsj&#39;:
    ...texture-mapping/shader.cpp:96: undefined reference to `_imp____glewCreateShader&#39;
    ...texture-mapping/shader.cpp:109: undefined reference to `_imp____glewShaderSource&#39;
    ...texture-mapping/shader.cpp:110: undefined reference to `_imp____glewCompileShader&#39;
    CMakeFiles\texture_mapping.dir/objects.a(texture.cpp.obj): In function `ZN7Texture4BindEj&#39;:
    ...texture-mapping/texture.cpp:36: undefined reference to `_imp____glewActiveTexture&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x24): undefined reference to `SDL_SetMainReady&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x55): undefined reference to `SDL_malloc&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x84): undefined reference to `SDL_wcslen&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xa5): undefined reference to `SDL_iconv_string&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xcf): undefined reference to `SDL_free&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xf4): undefined reference to `SDL_wcslen&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x10f): undefined reference to `SDL_iconv_string&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x143): undefined reference to `SDL_malloc&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x17f): undefined reference to `SDL_free&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x18b): undefined reference to `SDL_free&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x1d6): undefined reference to `SDL_isspace&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x295): undefined reference to `SDL_isspace&#39;
    ...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x3a2): undefined reference to `SDL_ShowSimpleMessageBox&#39;

Basically, errors with every usage of SDL and glew, but not glm, which is strange.

What am I doing wrong with my `CMakeLists.txt`?

  [1]: http://i.stack.imgur.com/Bp3No.png

Content Type	Original Author	Original Content on Stackoverflow
Question	varun	View Question on Stackoverflow
Solution 1 - Opengl	datenwolf	View Answer on Stackoverflow

What is the difference between FreeGLUT vs GLFW?

Opengl Problem Overview

Opengl Solutions

Solution 1 - Opengl

Ansible: In a playbook, filter a role by tag(s) without passing at the command-line

How to schedule tcpdump to run for a specific period of time?

Attributions