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What is OpenGL ?
- 1. What is OpenGL? KOLIBER
- 2. OpenGL ( OpenGraphics Library ) • Is a cross-language, cross-platformAPI for rendering 2D and 3D vector graphics.The API is typically used to interact with a graphics processing unit (GPU), to achieve hardware-accelerated rendering • the people who make GPUs, are responsible for writing implementations of the OpenGL rendering system.Their implementations, commonly called "drivers“ , translate OpenGL API commands into GPU commands
- 3. OpenGL History • Developmentstarted by SGI (Silicon Graphics INC.) at 1991 ( developers groups name was ARB ( IBM , Microsoft , Nvidia , … ) • First release at 1992 ( OpenGL 1.0 ) • Last release by SGI at 2 July 2006 ( OpenGL 2.1 ) • Maintainer changed at July 2006 ( from SGI to Khronos Group( SGI , ATI , Nvidia , … ) ) • First big release by Khronos at 11 Agust 2008 ( OpenGL 3.0 ) • Last release by Khronos at 31 July 2017 ( OpenGL 4.6 )
- 4. OpenGL usages Games AnimationsandVideos virtual realityCAD (Computer Aided Design ) Mobile phones
- 5. OpenGL Libraries • gl:OpenGL Core library ( rendering , drawing vertices , … ) • glu: OpenGL Utility library ( transforming , rotating , mathematical operations over GPU , … ) • glut: OpenGL Utility Toolkit library ( multiplatform window system interface ) • wgl,cgl,glx: Advance window system interface for OS (windows , *unix , mac , … )
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- 7. OpenGL implementations • NvidiaOpenGL ( called nvidia driver – for nvidia GPUs ) • AMD OpenGL ( called amd driver – for amd GPUs ) • Mesa3D ( open source opengl implementation for Intel HD graphics )
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- 9. Some questions • Whatis GPU ? Like CPUs , GPUs are processors , but for huge processes like rendering • What is Rendering ? Rendering means the process of translating 2D or 3D geometry to raster Image • Is GPU only for rendering ? Of course not , GPGPU ( general purpose graphics processing unit ) , is the use of a GPU to perform computation in applications traditionally handled by the CPU
- 10. Some questions • CPUvs GPU ? As we know CPUs are devided by brands (Intel , AMD , …) , ISAs (CISC , RISC , ZISC , MISC , …) , … , GPUs can be devided by parameters such brands ( Nvidia , Intel , AMD , … ) , Architectures (Kepler , Maxwell , Pascal ,Volta , … ) and etc • Can we write an application for GPU ? Like CPUs that have compiler ( translating high-level language to assembly ( clang , gcc , cc , … ) ) and assembler ( translate assembly to machine code ( nasm , yasm , … ) ) , GPUs are programmable , too and have compiler ( nvcc , hcc , … ) and assembler ( gcnasm , asfermi , … ) • What is OpenGL for ? For writing applications with interacting to GPU for rendering , we need deep knowledge about our GPU Architecture and hardware to create a simple application , renders a model , so OpenGL is a higher level API for simple interacting with GPU
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- 12. OpenGL rendering pipeline •At the first level OpenGL gets vertex array of our model and our texture coordinates or ( color and coordinates ) • At the second level OpenGL will translate , rotate , scale our vertices based on the transformation and perspective matrices ( position calculator ) • At the third level OpenGL assembles our vertices into triangles based on primitive type • At the fourth level OpenGL rasterizes our triangles into pixel format based on view port matrices and • At the fifth level OpenGL will colorize and texturize our pixels ( called fragment shader or pixel shader ) ( color chooser ) • At the sixth level OpenGL will test our pixels and do some blending operations and at the end will write pixels into framebuffer for showing in display
- 13. OpenGL rendering pipeline Vertexshader ( position calculator ) Fragment shader (color chooser ) Another simple view of OpenGL pipeline
- 14. OpenGL rendering pipeline Primitivetypes for triangle assembling at level two
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- 17. Testing ? Some time’sOpenGL may fail to rendering correctly like this picture The DepthTest is a per-sample processing operation performed after the Fragment Shader for detecting incorrect frames and discarding them .
- 18. An important question! How can you render this simple wall ? How many triangles you need to render it ? 100 ? 1000 ? Millions ? Oh is wrong to use Millions of triangles for rendering a simple wall ! So how can you ? Of course ! Textures You can use a simple rectangle and map this image on it ( called texture mapping )
- 19. An important question! OpenGL texture mapping
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- 21. Resources • https://www.khronos.org/ • https://www.wikipedia.org/ •https://www.mesa3d.org/ • https://code.tutsplus.com/