opengl - Changing color using a shader -

i writing deferred shader , 1 of first steps, familiar glsl , using shaders , framebuffer trying change color of mesh through shader. have linked 1 of buffers calling gldrawbuffers array holds attachement , binding texture framebuffer:

    glreadbuffer(gl_none);     glint color_loc = glgetfragdatalocation(pass_prog,"out_color");     glenum draws [1];     draws[color_loc] = gl_color_attachment0;     gldrawbuffers(1, draws);      glbindtexture(gl_texture_2d, diffusetexture);         glframebuffertexture(gl_framebuffer, draws[color_loc], diffusetexture, 0); 

i have out_color variable in fragment shader (otherwise wouldn't compile), can't manage change color of mesh setting through variable inside shader. has idea why , explain me?

thanks

edit: shaders: vertex shader

    #version 330   uniform mat4x4 u_model; uniform mat4x4 u_view; uniform mat4x4 u_persp; uniform mat4x4 u_invtrans;  in  vec3 position; in  vec3 normal;  out vec3 fs_normal; out vec4 fs_position;  void main(void) {     fs_normal = (u_invtrans*vec4(normal,0.0f)).xyz;     vec4 world = u_model * vec4(position, 1.0);     vec4 camera = u_view * world;     fs_position = camera;     gl_position = u_persp * camera; } 

fragment shader

    #version 330  uniform float u_far;  in vec3 fs_normal; in vec4 fs_position;  out vec4 out_normal; out vec4 out_position; out vec4 out_color;  void main(void) {     out_normal = vec4(normalize(fs_normal),0.0f);     out_position = vec4(fs_position.xyz,1.0f); //tuck position 0 1 range     out_color = vec4(1.0f, 0.0f, 0.0f, 1.0f);//first 3 diffuse, last specular } 

and not doing deferred shader in order learn glsl. learning glsl in order make deferred shader. =)

more source code setting textures:

glactivetexture(gl_texture0);  glgentextures(1, &depthtexture); glgentextures(1, &normaltexture); glgentextures(1, &positiontexture); glgentextures(1, &diffusetexture);  //depth texture glbindtexture(gl_texture_2d, depthtexture); gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_nearest); gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_nearest); gltexparameterf(gl_texture_2d, gl_texture_wrap_s, gl_clamp); gltexparameterf(gl_texture_2d, gl_texture_wrap_t, gl_clamp); gltexparameteri(gl_texture_2d, gl_depth_texture_mode, gl_intensity); glteximage2d( gl_texture_2d, 0, gl_depth_component, w, h, 0, gl_depth_component, gl_float, 0);  //normal texture glbindtexture(gl_texture_2d, normaltexture);     gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_linear); gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_linear);    gltexparameterf(gl_texture_2d, gl_texture_wrap_s, gl_clamp); gltexparameterf(gl_texture_2d, gl_texture_wrap_t, gl_clamp);         glteximage2d( gl_texture_2d, 0, gl_rgb32f , w, h, 0, gl_rgba, gl_float,0);  //position texture glbindtexture(gl_texture_2d, positiontexture);   gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_linear); gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_linear);    gltexparameterf(gl_texture_2d, gl_texture_wrap_s, gl_clamp); gltexparameterf(gl_texture_2d, gl_texture_wrap_t, gl_clamp);         glteximage2d( gl_texture_2d, 0, gl_rgb32f , w, h, 0, gl_rgba, gl_float,0);  //diffuse texture glbindtexture(gl_texture_2d, diffusetexture);    gltexparameteri(gl_texture_2d, gl_texture_min_filter, gl_linear); gltexparameteri(gl_texture_2d, gl_texture_mag_filter, gl_linear);    gltexparameterf(gl_texture_2d, gl_texture_wrap_s, gl_clamp); gltexparameterf(gl_texture_2d, gl_texture_wrap_t, gl_clamp);         glteximage2d( gl_texture_2d, 0, gl_rgb32f , w, h, 0, gl_rgba, gl_float,0);   //create framebuffer object glgenframebuffers(1, &fbo); glbindframebuffer(gl_framebuffer, fbo);   //instruct opengl won't bind color texture binded fbo glreadbuffer(gl_none); glint normal_loc = glgetfragdatalocation(pass_prog,"out_normal"); glint position_loc = glgetfragdatalocation(pass_prog,"out_position"); glint color_loc = glgetfragdatalocation(pass_prog,"out_color"); glenum draws [3]; draws[normal_loc] = gl_color_attachment0; draws[position_loc] = gl_color_attachment1; draws[color_loc] = gl_color_attachment2; gldrawbuffers(3, draws);  glbindtexture(gl_texture_2d, depthtexture);  glframebuffertexture(gl_framebuffer, gl_depth_attachment, depthtexture, 0); glbindtexture(gl_texture_2d, normaltexture);     glframebuffertexture(gl_framebuffer, draws[normal_loc], normaltexture, 0); glbindtexture(gl_texture_2d, positiontexture);     glframebuffertexture(gl_framebuffer, draws[position_loc], positiontexture, 0); glbindtexture(gl_texture_2d, diffusetexture);     glframebuffertexture(gl_framebuffer, draws[color_loc], diffusetexture, 0);    check fbo status fbostatus = glcheckframebufferstatus(gl_framebuffer); if(fbostatus != gl_framebuffer_complete) {     printf("gl_framebuffer_complete failed, cannot use fbo\n");     checkframebufferstatus(fbostatus); }    switch window-system-provided framebuffer glclear(gl_depth_buffer_bit|gl_depth_buffer_bit); glbindframebuffer(gl_framebuffer, 0); glbindtexture(gl_texture_2d, 0); 

edit: solved it. thanks.

you should this. assume out_color declared out vec4 out_color:

compile shaders , attach them program. glbindfragdatalocation(program, 0, "out_color"); gllinkprogram(program); gluseprogram(program);  glenum drawbuffers[1] = { gl_color_attachment0 } gldrawbuffers(1, drawbuffers);  setup fbo. 

the should work, if doesn't, post fragment shader , more source code. way, should creating deferred renderer learn glsl not idea. there easier ways learn glsl.