| 1 | = Visualization with OpenGL = |
| 2 | Essential approaches to programming computer graphics with Open Graphics |
| 3 | Language (OpenGL) graphics library are described. This document serves as |
| 4 | the basis for exercises in PRACE Summer of HPC Visualization training. |
| 5 | Rationale for giving introduction to OpenGL is that such knowledge is |
| 6 | important when developing codes that require some specific visualization |
| 7 | for which OpenGL can be handy. Programming Graphical Processing Unit |
| 8 | (GPU) through ''shaders'' is an important technique to accelerate |
| 9 | graphics and other embarrassing parallel problems. OpenGL evolved from |
| 10 | immediate mode to GPU only processing with the advent of OpenGL Shading |
| 11 | Language (GLSL). Introduction to the subject is given by recipes to |
| 12 | follow, discussing important techniques for visualization that can also |
| 13 | be extended to general GPU programming for parallel computing. Instead of |
| 14 | jumping to the latest OpenGL specification we use minimum required OpenGL |
| 15 | 2.1 with the extensions currently available on modest hardware and still |
| 16 | be able to use modern OpenGL 3.1+ programming principles. |
| 17 | |
| 18 | |
| 19 | == Introduction == |
| 20 | For the visualization of specific phenomena is usually not possible to use |
| 21 | a general purpose visualization tools. Such cases occur especially in the |
| 22 | visualization of engineering and physics problems. The modeling results are |
| 23 | usually not only simple function plots but complex objects such as graphs, |
| 24 | hierarchical structure, animation, motion mechanism, control channels, |
| 25 | volume models of specific forms, ... |
| 26 | |
| 27 | Through the time different standards were effective for computer graphics. |
| 28 | This is mainly due to the complexity of implementation and closed code in |
| 29 | the past. OpenGL remains the only widely accepted open standard, which was |
| 30 | first introduced on Silicon Graphics workstations (SGI). There exist also a |
| 31 | Microsoft Direct3D, which is limited to PCs with Windows and is not as easy |
| 32 | to use as OpenGL, which is due to its openness and capacity provided on all |
| 33 | operating systems and hardware platforms. OpenGL stagnated for some time |
| 34 | with upgrades to the original SGI specification. Many extensions previously |
| 35 | available from hardware vendors are now standardized with OpenGL 3+ where |
| 36 | things dramatically changed. ''Immediate mode'' programming where |
| 37 | communication from OS to GPU was regular practice and major obstacle to |
| 38 | graphics performance. Programming knowledge of OpenGL 1.x is therefore not |
| 39 | recommended for nowadays and can simply be forgotten and treated as legacy. |