Due to this, you should always give the whole rectangle to glViewport(). You absolutely can’t do one glViewport() on half the screen draw, then glViewport() the other half and draw again: impossible on all ES. glClear() will clear the whole FBO, not the rectangle given by glViewport(), unlike classic OGL.You cannot “come back” to a FBO and continue drawing. glBindFramebuffer() must be followed by glViewport() and glClear(), if not it will crash on most Mobile GPU.The bad news is Mobile OGL Drivers only manage one FBO context at a time, and a whole FBO or screen are always internally “tile managed” by the driver, with possibly “implicit superscalar Buffers”, which means for you: Writing on FBO, and using glViewport() and glClear() differ *Totally*.įramebuffer Objects ( FBO) is the official way to create offscreen bitmaps and offscreen rendering, and you can link them to a texture Id. and the GPU builder does not care because they just does no support after release. If you were used to hope for drivers updates on desktop to correct a bug or manage something differently, you have to know that GLES drivers are done once and for all for a given mobile GPU, quite often stands in ROMS and not in the system, and that basically the system (android,…) does not manage that part. No, the OpenGL ES driver will not be corrected by a system update in the future. OpenGL 3) … and yes, “ ES” means a lot of differences…Įverything in this document is both from OpenGL documentation, specific GPU documentations, and my own experience testing with any kind of models. OpenGL ES (quite the same as OpenGL1.x) and OpenGL ES2 (quite the same as. A lot of models, but only 2 API to program them all at the lowest level: Every iPhone, iPads from apple include a PowerVR, Raspberry Pi embeds a “VideoCore IV”, Android models use all those, plus a wide range of other GPU like NVidia Tegra, adreno, snapdragon. Some rendering with OpenGL ES 2: 4 passes and 4 shaders are used here.Īll Mobile devices today have something in common: a mobile Graphical Processor Unit (GPU) that can be programmed with OpenGL ES and OpenGL ES2. You need some OpenGL or 3D API background to understand what it’s about. This is an article to explain quickly the differences between OpenGL for desktop GPU and OpenGL ES(2) for Mobile GPU.
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