after creating context which supports multisampling i create FBO which resets GL_SAMPLE_BUFFERS value and i can’t use alpha to coverage option. if i render my scene without using FBO everything is fine. is there any solution for my problem?
When using an FBO, you replace the framebuffer you render to, and with it the multisample config and formats. To get multisampling with an FBO, you need to create a multisample FBO. The extension EXT_framebuffer_multisample allows you to create one and EXT_framebuffer_blit allows the multisampled framebuffer to be resolved to regular FBO.