# [`glvisnormals`][] A [GLSL][]/[OpenGL][] [\>=3.2][] [normal][] visualization library. A [geometry shader][] is used to visualize the normals from the same geometry as when drawing normally. [`glvisnormals`]: https://git.rcrnstn.net/rcrnstn/glvisnormals [GLSL]: https://en.wikipedia.org/wiki/OpenGL_Shading_Language [OpenGL]: https://en.wikipedia.org/wiki/OpenGL [\>=3.2]: https://en.wikipedia.org/wiki/OpenGL#Version_history [normal]: https://en.wikipedia.org/wiki/Normal_(geometry) [geometry shader]: https://www.khronos.org/opengl/wiki/Geometry_Shader ## Requirements [Geometry shader][]s require OpenGL [\>=3.2][] or the [`ARB_geometry_shader4`][] extension. [`ARB_geometry_shader4`]: https://www.khronos.org/registry/OpenGL/extensions/ARB/ARB_geometry_shader4.txt ## Usage Link the shader program with: - `visnormals.vert` - `visnormals.geom` - `visnormals.frag` The following vertex attributes need to be set: - `vec3 vert_position` - `vec3 vert_normal` (assumed to be of unit length) - `mat4 vert_model` (assumed to be an isometry, i.e. no scaling or skewing) The following uniforms need to be set: - `mat4 view_projection` - `float scale` - `vec4 color` The following outputs are written by the fragment shader: - ` vec4 frag_color` Make the shader program current and issue the same draw call as would be done when drawing normally. ## Build system This project has support for [CMake][], and uses [`cmake-cxx`][]. There are several ways to use this project in another CMake-based project: - Use [`FetchContent`][] to download it and import the targets automatically as part of the configure step: ```cmake include(FetchContent) FetchContent_Declare(project-name GIT_REPOSITORY https://example.com/user/project-name ) FetchContent_MakeAvailable( project-name ) ``` - Bundle it and import the targets with [`add_subdirectory`][]. - Use [`find_package`][] (requires that the project is [packaged](#packaging) or [installed](#installing)). As usual, use [`add_dependencies`][]/[`target_link_libraries`][] to declare the dependency. [CMake]: https://cmake.org [`cmake-cxx`]: https://git.rcrnstn.net/rcrnstn/cmake-cxx [`FetchContent`]: https://cmake.org/cmake/help/v3.14/module/FetchContent.html [`add_subdirectory`]: https://cmake.org/cmake/help/v3.14/command/add_subdirectory.html [`find_package`]: https://cmake.org/cmake/help/v3.14/command/find_package.html [`add_dependencies`]: https://cmake.org/cmake/help/v3.14/command/add_dependencies.html [`target_link_libraries`]: https://cmake.org/cmake/help/v3.14/command/target_link_libraries.html ### Configure and generate To configure and generate a build tree, use `cmake`: ```sh cmake -B build ``` To set the [`CMAKE_BUILD_TYPE`][], pass e.g. `-DCMAKE_BUILD_TYPE=Release`. [`cmake`]: https://cmake.org/cmake/help/v3.14/manual/cmake.1.html#generate-a-project-buildsystem [`CMAKE_BUILD_TYPE`]: https://cmake.org/cmake/help/v3.14/variable/CMAKE_BUILD_TYPE.html ### Build To build, use [`cmake --build`][]: ```sh cmake --build build ``` [`cmake --build`]: https://cmake.org/cmake/help/v3.14/manual/cmake.1.html#build-a-project ### Test To run tests, use [`ctest`][]: ```sh (cd build && ctest --output-on-failure) ``` [`ctest`]: https://cmake.org/cmake/help/v3.14/manual/ctest.1.html ### Package To package, use [`cpack`][]: ```sh (cd build && cpack) ``` [`cpack`]: https://cmake.org/cmake/help/v3.14/manual/cpack.1.html ### Install To install onto the current system, use [`cmake --install`][]: ```sh cmake --install build ``` [`cmake --install`]: https://cmake.org/cmake/help/v3.14/manual/cmake.1.html#install-a-project ## License Licensed under the [ISC License][] unless otherwise noted, see the [`LICENSE`](LICENSE) file. [ISC License]: https://choosealicense.com/licenses/isc/