im trying to write a gl 3.0 program without deprecated gl functions.
however, i found that glsl 1.3 dosent support GL_EXT_geometry_shader4,
and i couldnt find any information about geometry shader from opengl 3.0 and nor glsl 1.3 specifiations.
so, how could we implement geometry shaders in forward mode?
Geometry shader (GL_ARB_geometry_shader4 or GL_EXT_geometry_shader4) is not in GL3 core. You will need to use as extension - load needed entrypoints with wglGetProcAddress (under Windows). Or use glew or GLee that will simplify this process.