OpenGL basics
- 2. What is OpenGL ? ( Open Graphics Library ) • Cross-language, Cross-Platform API for rendering 2D, 3D vector graphics. • The API is typically used to interact with a graphics processing unit (GPU), to achieve hardware-accelerated rendering. • Drivers: 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 usages Games Animations and Videos virtual realityCAD (Computer Aided Design ) Mobile phones
- 4. OpenGL platforms Desktop Operation Systems (OpenGL) Embeded Devices (OpenGLES)
- 6. OpenGL history • 1991: Development started by SGI (Silicon Graphics INC. – ARB group (IBM , Microsoft , Nvidia , … )) • 1992: OpenGL 1.0 launched (fixed functions/pipeline - legacy) • 2000: OpenGL/ES 1.0 launched (embedded systems) • 2004: OpenGL 2.0 released (programmable pipeline - GLSL/ shaders) • 2005: OpenGL/SC 1.0 launched (safety critical) • 2006: OpenGL 2.1 released (last release by SGI - to Khronos Group) • 2008: OpenGL 3.0 released (first release by Khronos) • 2016: Vulkan 1.0 launched (by Khronos – low driver overhead) • 2017: OpenGL 4.6 released (last release by Khronos)
- 9. Deep into base !
- 10. 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
- 11. OpenGL rendering pipeline (Vertex/Fragment shader) Vertex shader ( position calculator ) Fragment shader (color chooser ) Another simple view of OpenGL pipeline
- 12. OpenGL rendering pipeline (Triangle assembling) Primitive types for triangle assembling at level two
- 13. OpenGL rendering pipeline (Testing) – OpenGL/SC
- 14. An important question ! (Texture mapping)
- 15. An important question ! (Texture mapping) OpenGL texture mapping
- 16. OpenGL rendering pipeline (Vertex shader – Projection)
- 17. Deep into Vertex Shader!
- 18. Vertex Shaders (MVP) • Model Matrix: Per model (Model position) • View Matrix: Camera position • Projection Matrix: Camera projection (Orthographic, Perspective, …) • ModelView Matrix: Old versions of OpenGL (View*Model)
- 20. Transformation matrices (T) • Scale • Rotation • Translation • Scissors • Reflection • ... PerspectiveRotate, Scale, Reflection, … ScaleTranslation
- 21. Vertex Shader – Model Transformation Matrix
- 22. Vertex Shader – View Transformation Matrix
- 23. Vertex Shader – View Transformation Matrix (World transforms) Camera (View) is fixed at Origin
- 24. Vertex Shader – Projection Transformation Matrix • Perspective • Orthographic • …
- 25. Vertex Shader – Projection Transformation Matrix(Perspective) • N: near • F: far • L: left • T: top • B: bottom • R: right
- 26. Vertex Shader – Projection Transformation Matrix
- 27. Fragment Shader - Lighting
- 28. Let’s Code!
- 29. OpenGL libraries • GL: OpenGL Core library ( rendering , drawing vertices , … ) (low level API) • GLU: OpenGL Utility library ( transforming , rotating , mathematical operations over GPU , … ) (higher level API) • GLUT: OpenGL Utility Toolkit library ( multiplatform window system interface ) • GLFW: Graphics Library Frameword( multiplatform window system interface ) (Handles joysticks, keyboard, mouse, …) • SDL, FLTK, QT • WGL, CGL, GLX
- 30. OpenGL libraries
- 31. OpenGL functions (gl.h) • glVertex*(…) • glColor*(…) • glRotate*(…) • glTranslate*(…) • glScale*(…) • glBegin(…) • glEnd() • glMatrixMode(…) • glPushMatrix() • glPopMatrix() • glLoadIdentity() • glOrtho(…) • glFrustum(…) • glEnable(…) • glDisable(…) • glLight*(…)
- 33. Any question ?
- 34. Resources • https://www.khronos.org/ • https://www.wikipedia.org/ • https://www.mesa3d.org/ • https://code.tutsplus.com/ • https://learnopengl.com • https://open.gl/context • http://www.songho.ca/opengl/gl_transform.html#example1 • http://in2gpu.com/2015/05/13/the-model-matrix/ • http://www.lighthouse3d.com/tutorials/glut-tutorial/keyboard-example-moving- around-the-world/ • https://webglfundamentals.org/webgl/lessons/webgl-3d-camera.html