ios - GLKit Offscreen render to texture not working -

when try create fbo texture attached in opengl es 2.0 this:

    glgenframebuffers(1, &framebuffer);     glgentextures(1, &textureid);      glbindframebuffer(gl_framebuffer, framebuffer);      glbindtexture(gl_texture_2d, textureid);     glteximage2d(gl_texture_2d, 0, gl_rgba, width, height, 0, gl_rgba, gl_unsigned_byte, null);      gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_linear);     gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_linear);     gltexparameteri(gl_texture_2d, gl_texture_wrap_s, gl_clamp_to_edge);     gltexparameteri(gl_texture_2d, gl_texture_wrap_t, gl_clamp_to_edge);      glframebuffertexture2d(gl_framebuffer, gl_color_attachment0, gl_texture_2d, framebuffer, 0);      glenum status;     status = glcheckframebufferstatus(gl_framebuffer);     switch(status) {         case gl_framebuffer_complete:             nslog(@"fbo complete");             break;          case gl_framebuffer_unsupported:             nslog(@"fbo unsupported");             break;          default:             /* programming error; fail on hardware */             nslog(@"framebuffer error");             break;     }      glbindtexture(gl_texture_2d, 0);     glbindframebuffer(gl_framebuffer, 0); 

and apply this:

    glbindframebuffer(gl_framebuffer, rendertarget.framebufferid);     glbindtexture(gl_texture_2d, rendertarget.textureid);      glviewport(0, 0, rendertarget.width, rendertarget.height); 

then render on , draw attached texture screen. result empty black screen (everything works fine if render screen directly). tried several fbo tutorials (the current code 1 of them) no difference.

also when use opengl debugger xcode have warnings like: "slow framebuffer load issue" on gldrawarrays can see texture not empty (i can see texture right size , right glclearcolor)

would great if had issue before , knows im doing wrong here :)

thanks in advance

ok solved problem. there few smaller problems main problem bound framebuffer , texture (see top related question). other problem $!&()#^ (i mean wonderful) opengl coordinate system (bottom left) quick fix. working fine expect of poor performance when drawing fullscreen quad, open question that.