iphone - How to disable or configure clipping when rendering to texture using FBO in OpenGL? -

i have question way fbo clips visible scene. happens in iphone's opengl es.

i'm rendering in 2d , using render-to-texture fbo.

i find when part of scene passes side of rectangle of screen size (480*320) appears clipped fbo generated texture.

why that? how disable or configure it?

i've tried disabling scissor test

ldisable(gl_scissor_test);

i've tried set needed section by

`glenable(gl_scissor_test); glscissor(0, 0, 100, 100);` 

i've tried adjust viewport by

glviewport(0,0, 512,512);

it doesn't work needed. instead of extending render area needed 512*512 looks still clips area 480*320 , stretches afterwards 512*512

all these didn't bring needed result.

in code: create texture

gluint textureid;    glenable(gl_texture_2d); glenable(gl_blend);  glgentextures(1, &textureid); glbindtexture(gl_texture_2d, textureid);  gltexparameteri(gl_texture_2d,gl_texture_min_filter,gl_linear);  gltexparameteri(gl_texture_2d,gl_texture_mag_filter, gl_nearest);  glteximage2d(gl_texture_2d, 0, gl_rgba, 512, 512, 0, gl_rgba, gl_unsigned_byte, nil);` 

create fbo , attach texture it

gluint textureframebuffer; glint prevfbo; glgetintegerv(gl_framebuffer_binding_oes, &prevfbo);  // create framebuffer glgenframebuffersoes(1, &textureframebuffer); glbindframebufferoes(gl_framebuffer_oes, textureframebuffer);  // attach renderbuffer glframebuffertexture2does(gl_framebuffer_oes, gl_color_attachment0_oes, gl_texture_2d, textureid, 0);  if(glcheckframebufferstatusoes(gl_framebuffer_oes) != gl_framebuffer_complete_oes)     nslog(@"error - while creating fbo");  // unbind frame buffer glbindframebufferoes(gl_framebuffer_oes, prevfbo); 

and then, when draw stuff fbo , render square texture,

static const float textcoords[] =  {     0, 1,     1, 1,     0, 0,     1, 0, };  static const float quadverts[] =  {     0, 320,     320, 320,     0, 0,     320, 0, }; glenable(gl_texture_2d);     glbindtexture(gl_texture_2d, textureid);     glvertexpointer(2, gl_float, 0, quadverts); gltexcoordpointer(2, gl_float, 0, textcoords);       gldrawarrays(gl_triangle_strip, 0, 4); 

to opinion should see square filled stuff had drawn fbo. whereas, see part of – clipped rectangle of size 480x320 @ lower left corner. so, question steel actual

you need change viewport doing:

glviewport(0,0,texturewidth,textureheight); 

edit: , don't forget switch normal value after rendering onto fbo.

/// save viewport glint vp[4]; glgetintegerv(gl_viewport, vp);  /// restore viewport glviewport(vp[0], vp[1], vp[2], vp[3]);