difference between opengl es 2.0 and 3.0

Yep that was in one of Eric's Anholt's first posts, breaking up quads into triangles. In OpenGL polygons with four or more vertices have to be decomposed into triangles first It's impressive when you see everything drawn by shaders alone (the entire screen is just drawn as two triangles covering the window), just think how slow it would be if the CPU was drawing the scene pixel by pixel.

Vertex shaders are just programs that transform vertices from object space to view space and fragment shaders are programs that generate the colour to use for each pixel of a triangle drawn. Shaders aren't all the complicated if you don't need them to be. OpenG元.1 was also the point where the fixed-function vertex and fragment sections were finally removed (they were deprecated in 3.0). Those higher order polygons were then also removed from OpenGL as of version 3.1.

In OpenGL polygons with four or more vertices have to be decomposed into triangles first (on the old 3dfx even lines were triangles, a line was drawn by drawing a triangle with two identical vertices), OpenGLES made the move to remove all higher order polygons from the start since it reduces complexity of the drivers and makes it the programmer's responsibility to convert higher order polygons into triangles. Then Tim comes along and throws shaders into the mix. There is no library like FreeGLUT for OpenGLES. I wondered why there was nothing between triangles and cubes and full objects in OpenGLES. It would be interesting to see the differences between VC4 and VC6 QPU code for the same shader, I assume VC6 has more instructions, I know it has more registers).īeen putting off learning 3D on Pi's, it has been playing with OpenGL on the Pi4 that all the pieces fell into place. It won't tell you how GLSL compiles into QPU code and register setups, for that read the Mesa source, though it compiles GLSL into an intermediary format or two (GLSL->hir->nir I think) before finally generating QPU code and register settings. albeit without telling you about any bugs in the implementations. The VC4 manual tells you all about the QPUs (which are the processors that the shaders run on) and the texture units etc. It's likely that many of the shaders require features not available in the OpenGLES2 shaders. So far reading all the OpenGL books is leading me to conclude shaders are even more complex than just the 3D stuff. Think I need to look at the output of the shader compilers. It looks like mesa is smart enough to figure that out and use the VC4 driver.ĭug out the VC4 manual, not much on shaders, need the VC6 manual, not that it will make much sense. In Tim's Readme it says only works on Pi4's. What gave you the impression that the VC4 didn't have shaders?

Difference between opengl es 2.0 and 3.0