SDL OpenGL in C++, Texture Shader missing the texture -

i trying create first opengl shader experiencing difficulties when trying add texture cube object.

is sharp eyed enough spot error? code might have lots of errors, , grateful if points them out, interested in why rotating cube gray , not colorful.

(i have skipped error handling keep source code size low, sorry that)

**edit found out missed uv settings, still gray cube though ...

#include <windows.h> #include <sdl.h>  #include <gl/glew.h> #include <gl/glu.h> #include <gl/glut.h>  #include <math.h> #include <string>  using namespace std;  void            initall(); void            setupbox(); void            mainloop(); unsigned int    generatetexture(); void            handle_inputs(); void            updatescreen(); void            clean_up();  int             scrwidth, scrheight, flags; bool            bquit = false; float           angle = 0.0f;  gluint          tex_box, tex_norm;  std::string     vertex_source, fragment_source; gluint          shader_program, vertex_shader, fragment_shader;  // vao , vbo handle gluint          vao, vbo;  const char      *source; int             length;  struct svert {     float x;     float y;     float z; };  class cpolygon { public:     int v[4];      void fillverts(int v1, int v2, int v3, int v4) {         v[0] = v1;         v[1] = v2;         v[2] = v3;         v[3] = v4;     } } p[6];  svert pv[8];  int main(int argc, char *argv[]) {     initall();     mainloop();     clean_up();     return 0; }  void initall() {     scrwidth = 800;     scrheight = 600;      vertex_source =         "#version 330\n"         "layout (location = 0) in vec3 position;\n"         "layout (location = 1) in vec2 texcoord;\n"         "void main() {\n"         "   gl_position = gl_modelviewprojectionmatrix * gl_vertex;\n"          "   gl_texcoord[0] = gl_multitexcoord0;\n"         "}\n";      fragment_source =         "#version 330\n"         "uniform sampler2d tex;\n"         "void main() {\n"         "   fragcolor = texture2d(tex, gl_texcoord[0].st);\n"         "}\n";      sdl_initsubsystem(sdl_init_video);     sdl_gl_setattribute( sdl_gl_alpha_size, 8 );     sdl_gl_setattribute( sdl_gl_red_size, 8 );     sdl_gl_setattribute( sdl_gl_green_size, 8 );     sdl_gl_setattribute( sdl_gl_blue_size, 8 );     sdl_gl_setattribute( sdl_gl_depth_size, 16 );     sdl_gl_setattribute( sdl_gl_doublebuffer, 1 );      flags = sdl_opengl | sdl_anyformat ;      sdl_setvideomode(scrwidth, scrheight, 16, flags);      glmatrixmode( gl_projection );     glloadidentity( );     gluperspective( 45.0f, (glfloat)scrwidth/(glfloat)scrheight, 1.0f, 500.0f );     glmatrixmode( gl_modelview );     glloadidentity( );      glenable (gl_depth_test);     glenable (gl_lighting);     glenable (gl_light0);      glenable(gl_blend);     glblendfunc(gl_src_color, gl_one_minus_src_alpha);      sdl_wm_setcaption( "texture shader", null );      glewinit();      // vertex shader     vertex_shader = glcreateshader(gl_vertex_shader);     source = vertex_source.c_str();     length = vertex_source.size();     glshadersource(vertex_shader, 1, &source, &length);      glcompileshader(vertex_shader);      // fragment shader     fragment_shader = glcreateshader(gl_fragment_shader);     source = fragment_source.c_str();     length = fragment_source.size();     glshadersource(fragment_shader, 1, &source, &length);     glcompileshader(fragment_shader);      // create program     shader_program = glcreateprogram();     glattachshader(shader_program, vertex_shader);     glattachshader(shader_program, fragment_shader);     gllinkprogram(shader_program);      glgenvertexarrays(1, &vao);     glbindvertexarray(vao);      glgenbuffers(1, &vbo);     glbindbuffer(gl_array_buffer, vbo);      setupbox();      glfloat vd[6*5*6];      for(int pi=0; pi<6; pi++)     {         vd[pi*30+ 0] = pv[ p[pi].v[0] ].x;         vd[pi*30+ 1] = pv[ p[pi].v[0] ].y;         vd[pi*30+ 2] = pv[ p[pi].v[0] ].z;          vd[pi*30+ 3] = 0.0;         vd[pi*30+ 4] = 1.0;          vd[pi*30+ 5] = pv[ p[pi].v[1] ].x;         vd[pi*30+ 6] = pv[ p[pi].v[1] ].y;         vd[pi*30+ 7] = pv[ p[pi].v[1] ].z;          vd[pi*30+ 8] = 0.0;         vd[pi*30+ 9] = 0.0;          vd[pi*30+10] = pv[ p[pi].v[2] ].x;         vd[pi*30+11] = pv[ p[pi].v[2] ].y;         vd[pi*30+12] = pv[ p[pi].v[2] ].z;          vd[pi*30+13] = 1.0;         vd[pi*30+14] = 0.0;          vd[pi*30+15] = pv[ p[pi].v[0] ].x;         vd[pi*30+16] = pv[ p[pi].v[0] ].y;         vd[pi*30+17] = pv[ p[pi].v[0] ].z;          vd[pi*30+18] = 0.0;         vd[pi*30+19] = 1.0;          vd[pi*30+20] = pv[ p[pi].v[2] ].x;         vd[pi*30+21] = pv[ p[pi].v[2] ].y;         vd[pi*30+22] = pv[ p[pi].v[2] ].z;          vd[pi*30+23] = 1.0;         vd[pi*30+24] = 0.0;          vd[pi*30+25] = pv[ p[pi].v[3] ].x;         vd[pi*30+26] = pv[ p[pi].v[3] ].y;         vd[pi*30+27] = pv[ p[pi].v[3] ].z;          vd[pi*30+28] = 1.0;         vd[pi*30+29] = 1.0;     }      glbufferdata(gl_array_buffer, sizeof(glfloat)*6*5*6, vd, gl_static_draw);     glenablevertexattribarray(0);     glvertexattribpointer(0, 3, gl_float, gl_false, 5*sizeof(glfloat), (char*)0 + 0*sizeof(glfloat));     glenablevertexattribarray(1);     glvertexattribpointer(1, 2, gl_float, gl_false, 5*sizeof(glfloat), (char*)0 + 3*sizeof(glfloat));      tex_box = generatetexture();     tex_norm = generatetexture(); }  void setupbox() {     (int z=0;z<2;z++)     (int y=0;y<2;y++)     (int x=0;x<2;x++)     {         pv[x+y*2+z*4].x = -1.0+x;         pv[x+y*2+z*4].y = -1.0+y;         pv[x+y*2+z*4].z = -1.0+z;     }      p[0].fillverts (0, 1, 3, 2);    // above     p[1].fillverts (4, 5, 1, 0);    // behind     p[2].fillverts (6, 7, 3, 2);    // in front     p[3].fillverts (5, 7, 3, 1);    // right     p[4].fillverts (0, 2, 6, 4);    // left     p[5].fillverts (7, 6, 4, 5);    // below }  unsigned int generatetexture() {     byte    data[128*128*3];     unsigned int id;      (int x=0;x<128;x++)         (int y=0;y<128;y++)         {             data[y*128*3+x*3+0] = x;        // red             data[y*128*3+x*3+1] = y;        // green             data[y*128*3+x*3+2] = 128-(abs(64-x)+abs(64-y));    // blue         }      glgentextures(1, &id);      glbindtexture(gl_texture_2d, id);      gltexenvf( gl_texture_env, gl_texture_env_mode, gl_modulate );     gltexparameteri( gl_texture_2d, gl_texture_mag_filter, gl_nearest);      gltexparameteri( gl_texture_2d, gl_texture_min_filter, gl_nearest);      gltexparameterf( gl_texture_2d, gl_texture_wrap_s, gl_repeat );     gltexparameterf( gl_texture_2d, gl_texture_wrap_t, gl_repeat );     glteximage2d(gl_texture_2d, 0, gl_rgb, 128, 128, 0, gl_rgb, gl_unsigned_byte, data);     glgeneratemipmap(gl_texture_2d);      return id; }  void mainloop() {     while(bquit == false)     {         handle_inputs();         updatescreen();         angle += 1.5f;         sleep(50);     } }  void handle_inputs() {     sdl_pumpevents();     uint8 * keystate = sdl_getkeystate(null);     if(keystate[sdlk_escape]) bquit = true; }  void updatescreen() {     glclear(gl_color_buffer_bit | gl_depth_buffer_bit);     glloadidentity();     glulookat (2.0, 2.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);     gluseprogram(shader_program);     glbindvertexarray(vao);      glrotatef(angle, 1.0, 0.0, 0.0); //rotate on x axis     glrotatef(angle, 0.0, 1.0, 0.0); //rotate on y axis     glrotatef(angle, 0.0, 0.0, 1.0); //rotate on z axis      glactivetexture(gl_texture0);     int loc = glgetuniformlocation(shader_program, "tex");     gluniform1i(loc, 0);     glbindtexture(gl_texture_2d, tex_box);     gldrawarrays(gl_triangles, 0, 6*6);     //glutsolidteapot(2.0);     gluseprogram(0);     sdl_gl_swapbuffers(); }  void clean_up() {     gldeletevertexarrays(1, &vao);     gldeletebuffers(1, &vbo);      gldetachshader(shader_program, vertex_shader);     gldetachshader(shader_program, fragment_shader);     gldeleteshader(vertex_shader);     gldeleteshader(fragment_shader);     gldeleteprogram(shader_program);      sdl_quitsubsystem(sdl_init_video);     gldeletetextures(1, &tex_box);     gldeletetextures(1, &tex_norm);     sdl_quit(); } 

**edit 2 here fixed version result following advices in derhass accepted answer. upvote answer instead of if it.

#include <windows.h> #include <sdl.h>  #include <gl/glew.h> #include <gl/glu.h> #include <gl/glut.h> #include <stdio.h>  #include <math.h> #include <string>  using namespace std; #define log_size 10000  void            initall(); void            setupbox(); void            mainloop(); unsigned int    generatetexture(); void            handle_inputs(); void            updatescreen(); void            clean_up(); void            dbpf(int, const char *, ...);  int             scrwidth, scrheight, flags; bool            bquit = false; float           angle = 0.0f;  va_list         m; int             db_threashold = 0; glint           status; glchar          elog[log_size]; glint           rlength = 0;  gluint          tex_box, tex_norm;  std::string     vertex_source, fragment_source; gluint          shader_program, vertex_shader, fragment_shader;  gluint          vao, vbo;  const char      *source; int             length;  struct svert {     float x;     float y;     float z; };  class cpolygon { public:     int v[4];      void fillverts(int v1, int v2, int v3, int v4) {         v[0] = v1;         v[1] = v2;         v[2] = v3;         v[3] = v4;     } } p[6];  svert pv[8];  int main(int argc, char *argv[]) {     initall();     mainloop();     clean_up();     return 0; }  void initall() {     scrwidth = 800;     scrheight = 600;      vertex_source =         "#version 330\n"         "in vec3 position;\n"         "in vec2 texcoord;\n"         "out vec3 ocolor;"         "out vec2 otexcoord;"         "void main() {\n"         "    otexcoord = texcoord;\n"         "    gl_position = gl_modelviewprojectionmatrix*vec4(position, 1.0);\n"         "}\n";      fragment_source =         "#version 330\n"         "in vec2 otexcoord;"         "out vec4 ocolor;"         "uniform sampler2d tex;\n"         "void main() {\n"         "   ocolor = texture2d(tex, otexcoord);\n"         "}\n";      sdl_initsubsystem(sdl_init_video);     sdl_gl_setattribute( sdl_gl_alpha_size, 8 );     sdl_gl_setattribute( sdl_gl_red_size, 8 );     sdl_gl_setattribute( sdl_gl_green_size, 8 );     sdl_gl_setattribute( sdl_gl_blue_size, 8 );     sdl_gl_setattribute( sdl_gl_depth_size, 16 );     sdl_gl_setattribute( sdl_gl_doublebuffer, 1 );      flags = sdl_opengl | sdl_anyformat ;      sdl_setvideomode(scrwidth, scrheight, 16, flags);      glmatrixmode( gl_projection );     glloadidentity( );     gluperspective( 45.0f, (glfloat)scrwidth/(glfloat)scrheight, 1.0f, 500.0f );     glmatrixmode( gl_modelview );     glloadidentity( );      glenable (gl_depth_test);     glenable (gl_lighting);     glenable (gl_light0);      sdl_wm_setcaption( "texture shader", null );      glewinit();      // create , compiler vertex shader     vertex_shader = glcreateshader(gl_vertex_shader);     source = vertex_source.c_str();     length = vertex_source.size();     glshadersource(vertex_shader, 1, &source, &length);      glcompileshader(vertex_shader);      glgetshaderiv(vertex_shader, gl_compile_status, &status);     glgetshaderinfolog(vertex_shader, log_size, &rlength, elog);     dbpf(10, "compile vertex log: \n %s \n", elog);      // create , compiler fragment shader     fragment_shader = glcreateshader(gl_fragment_shader);     source = fragment_source.c_str();     length = fragment_source.size();     glshadersource(fragment_shader, 1, &source, &length);     glcompileshader(fragment_shader);      glgetshaderiv(fragment_shader, gl_compile_status, &status);     glgetshaderinfolog(fragment_shader, log_size, &rlength, elog);     dbpf(10, "compile fragment log: \n %s \n", elog);      // create program     shader_program = glcreateprogram();      // attach shaders     glattachshader(shader_program, vertex_shader);     glattachshader(shader_program, fragment_shader);      // link program , check errors     gllinkprogram(shader_program);     glgetprogramiv(shader_program, gl_link_status, &status);     glgetprograminfolog(shader_program, log_size, &rlength, elog);     dbpf(10, "link log: \n %s \n", elog);      // generate , bind vao     glgenvertexarrays(1, &vao);     glbindvertexarray(vao);      // generate , bind buffer object     glgenbuffers(1, &vbo);     glbindbuffer(gl_array_buffer, vbo);      setupbox();      glfloat vd[6*5*6];      for(int pi=0; pi<6; pi++)     {         vd[pi*30+ 0] = pv[ p[pi].v[0] ].x;         vd[pi*30+ 1] = pv[ p[pi].v[0] ].y;         vd[pi*30+ 2] = pv[ p[pi].v[0] ].z;          vd[pi*30+ 3] = 0.0;         vd[pi*30+ 4] = 1.0;          vd[pi*30+ 5] = pv[ p[pi].v[1] ].x;         vd[pi*30+ 6] = pv[ p[pi].v[1] ].y;         vd[pi*30+ 7] = pv[ p[pi].v[1] ].z;          vd[pi*30+ 8] = 0.0;         vd[pi*30+ 9] = 0.0;          vd[pi*30+10] = pv[ p[pi].v[2] ].x;         vd[pi*30+11] = pv[ p[pi].v[2] ].y;         vd[pi*30+12] = pv[ p[pi].v[2] ].z;          vd[pi*30+13] = 1.0;         vd[pi*30+14] = 0.0;          vd[pi*30+15] = pv[ p[pi].v[0] ].x;         vd[pi*30+16] = pv[ p[pi].v[0] ].y;         vd[pi*30+17] = pv[ p[pi].v[0] ].z;          vd[pi*30+18] = 0.0;         vd[pi*30+19] = 1.0;          vd[pi*30+20] = pv[ p[pi].v[2] ].x;         vd[pi*30+21] = pv[ p[pi].v[2] ].y;         vd[pi*30+22] = pv[ p[pi].v[2] ].z;          vd[pi*30+23] = 1.0;         vd[pi*30+24] = 0.0;          vd[pi*30+25] = pv[ p[pi].v[3] ].x;         vd[pi*30+26] = pv[ p[pi].v[3] ].y;         vd[pi*30+27] = pv[ p[pi].v[3] ].z;          vd[pi*30+28] = 1.0;         vd[pi*30+29] = 1.0;     }      // fill data     glbufferdata(gl_array_buffer, sizeof(glfloat)*6*5*6, vd, gl_static_draw);      // set generic attrib pointers     glenablevertexattribarray(0);     glvertexattribpointer(0, 3, gl_float, gl_false, 5*sizeof(glfloat), (char*)0 + 0*sizeof(glfloat));      glenablevertexattribarray(1);     glvertexattribpointer(1, 2, gl_float, gl_false, 5*sizeof(glfloat), (char*)0 + 3*sizeof(glfloat));      tex_box = generatetexture();     tex_norm = generatetexture();  }  void setupbox() {      (int z=0;z<2;z++)     (int y=0;y<2;y++)     (int x=0;x<2;x++)     {         pv[x+y*2+z*4].x = -1.0+x;         pv[x+y*2+z*4].y = -1.0+y;         pv[x+y*2+z*4].z = -1.0+z;     }      p[0].fillverts (0, 1, 3, 2);    // above     p[1].fillverts (4, 5, 1, 0);    // behind     p[2].fillverts (6, 7, 3, 2);    // in front     p[3].fillverts (5, 7, 3, 1);    // right     p[4].fillverts (0, 2, 6, 4);    // left     p[5].fillverts (7, 6, 4, 5);    // below }  unsigned int generatetexture() {     byte    data[128*128*3];     unsigned int id;      (int x=0;x<128;x++)         (int y=0;y<128;y++)         {             data[y*128*3+x*3+0] = x;        // red             data[y*128*3+x*3+1] = y;        // green             data[y*128*3+x*3+2] = 128-(abs(64-x)+abs(64-y));    // blue         }      glgentextures(1, &id);      glbindtexture(gl_texture_2d, id);      gltexenvf( gl_texture_env, gl_texture_env_mode, gl_modulate );      gltexparameteri( gl_texture_2d, gl_texture_mag_filter, gl_nearest);      gltexparameteri( gl_texture_2d, gl_texture_min_filter, gl_nearest);      gltexparameterf( gl_texture_2d, gl_texture_wrap_s, gl_repeat );     gltexparameterf( gl_texture_2d, gl_texture_wrap_t, gl_repeat );     glteximage2d(gl_texture_2d, 0, gl_rgb, 128, 128, 0, gl_rgb, gl_unsigned_byte, data);     glgeneratemipmap(gl_texture_2d);      return id; }  void mainloop() {     while(bquit == false)     {         handle_inputs();         updatescreen();         angle += 1.5f;         sleep(50);     } }  void handle_inputs() {     sdl_pumpevents();     uint8 * keystate = sdl_getkeystate(null);     if(keystate[sdlk_escape]) bquit = true; }  void updatescreen() {     glclear(gl_color_buffer_bit | gl_depth_buffer_bit);     glloadidentity();      glulookat (2.0, 2.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);      // use shader program     gluseprogram(shader_program);      // bind vao     glbindvertexarray(vao);      // rotation     glrotatef(angle, 1.0, 0.0, 0.0); //rotate on x axis     glrotatef(angle, 0.0, 1.0, 0.0); //rotate on y axis     glrotatef(angle, 0.0, 0.0, 1.0); //rotate on z axis      // bind texture     glactivetexture(gl_texture0);     int loc = glgetuniformlocation(shader_program, "tex");     gluniform1i(loc, 0);      glbindtexture(gl_texture_2d, tex_box);      // draw     gldrawarrays(gl_triangles, 0, 6*6);      gluseprogram(0);     sdl_gl_swapbuffers(); }  void clean_up() {     gldeletevertexarrays(1, &vao);     gldeletebuffers(1, &vbo);      gldetachshader(shader_program, vertex_shader);     gldetachshader(shader_program, fragment_shader);     gldeleteshader(vertex_shader);     gldeleteshader(fragment_shader);     gldeleteprogram(shader_program);      sdl_quitsubsystem(sdl_init_video);     gldeletetextures(1, &tex_box);     gldeletetextures(1, &tex_norm);     sdl_quit(); }  void dbpf(int t, const char * msg, ...) {     va_start(m, msg);     if (t >= db_threashold) vfprintf(stderr, msg, m);     va_end(m); } 

your fragment shader shouldn't compile. writing undeclated variable 'fragcolor'. should first add code check compile , link status, , query compile , link log, errors , warnings glsl compiler/linker detected. use like:

glint status; glubyte log[log_size]; // compile shader here ... glgetshaderiv(shader, gl_compile_status, &status); if (status != gl_true) {     // compile error     ... } glgetshaderinfolog(shader, log_size, 0, log); // print log  ... // link program here // ... glgetprogramiv(program, gl_link_status, &status); if (status != gl_true) {     //  error     ... } glgetprograminfolog(program, log_size, 0, log); // print log 

maybe want print info log in error case, there might warnings/hints in there in successful case, recommend printing alywas, @ least in debug/development builts.

i recommend stop mixing old, deprecated builtins gl_texcoord[0], gl_multitexcoord0 , on mordern user defined attributes, inputs , outputs. currently, not using texcoord attribute did declare.