c++ - Shape not being drawn in OpenGL when unbinding vertex array -

i'm learning opengl , set mesh class render shapes. drawing works without

glbindvertexarray(0); 

at end i'm guessing messed can't figure out.

here code: main.cpp

#include <gl/glew.h> #include <sdl2/sdl.h> #include <iostream> #include "mesh.h"  #define width 1280 #define height 720  // vertex shader     const char* vs = "\n\     #version 330                \n\     layout (location = 0) in vec2 position; \n\     layout (location = 1) in vec3 color;    \n\     out vec3 color;             \n\                         \n\     void main() {               \n\         color = color;          \n\         gl_position = vec4(position, 0.0, 1.0); \n\     }                   \n\                         \n\     "; // fragment shader     const char* fs = "\n\     #version 330                \n\     in vec3 color;              \n\     out vec4 fragcolor;             \n\                         \n\     void main() {               \n\     fragcolor = vec4(color, 1.0);       \n\     }                   \n\     ";  bool checkshader(gluint shader) {     glint status;     glgetshaderiv(shader, gl_compile_status, &status);      if (status != gl_true) {         char buffer[512];         glgetshaderinfolog(shader, 512, null, buffer);         std::cout << "error compiling shader:" << buffer << std::endl;         return false;     }     return true; }  bool compileshaders() {     // compile vertex shader     gluint vertexshader = glcreateshader(gl_vertex_shader);     glshadersource(vertexshader, 1, &vs, null);     glcompileshader(vertexshader);      if (!checkshader(vertexshader))         return false;      // compile fragment shader     gluint fragmentshader = glcreateshader(gl_fragment_shader);     glshadersource(fragmentshader, 1, &fs, null);     glcompileshader(fragmentshader);      if (!checkshader(fragmentshader))         return false;      gluint shaderprogram = glcreateprogram();     glattachshader(shaderprogram, vertexshader);     glattachshader(shaderprogram, fragmentshader);      glbindfragdatalocation(shaderprogram, 0, "outcolor");      gllinkprogram(shaderprogram);     gluseprogram(shaderprogram);      return true; }  int main() {     bool success = true;     bool running = true;      sdl_window* window;     sdl_glcontext context;      // initialize sdl/glew      if (sdl_init(sdl_init_video) <  0) {         std::cerr << "video initialization failed:" << sdl_geterror() << std::endl;         success = false;     }      sdl_gl_setattribute(sdl_gl_context_major_version, 3);     sdl_gl_setattribute(sdl_gl_context_minor_version, 3);     sdl_gl_setattribute(sdl_gl_doublebuffer, 1);     sdl_gl_setattribute(sdl_gl_depth_size, 24);      window = sdl_createwindow("game title", sdl_windowpos_centered,         sdl_windowpos_centered, width, height, sdl_window_shown |         sdl_window_opengl | sdl_window_borderless);     context = sdl_gl_createcontext(window);      glewexperimental = gl_true;      if (glewinit() != glew_ok) {         std::cerr << "problem initializing glew." << std::endl;         success = false;     }      sdl_event e;      // mesh setup     float vertices[] = { 0.0f, 0.5f, 1.0f, 0.0f, 0.0f,                  0.5f,-0.5f, 0.0f, 1.0f, 0.0f,                 -0.5f,-0.5f, 0.0f, 0.0f, 1.0f };      float vertices2[] = { -1.0f,-1.0f, 1.0f, 0.0f, 0.0f,                   -1.0f, 1.0f, 0.0f, 1.0f, 0.0f,                   -0.0f, 0.0f, 0.0f, 0.0f, 1.0f };      gluint elements[] = { 0, 1, 2 };      mesh triangle(vertices, elements, sizeof(vertices), sizeof(elements));     mesh triangle2(vertices2, elements, sizeof(vertices2), sizeof(elements));      if (!compileshaders())         success = false;      if (!success) {         std::cerr << "a problem ocurred during initialization, exit." << std::endl;         exit(1);     }      while (running) {         while (sdl_pollevent(&e)) {             if (e.type ==  sdl_quit)                 running = false;             if (e.type == sdl_keydown)                 if (e.key.keysym.sym == sdlk_escape)                     running = false;         }          glclearcolor(0.0f, 1.0f, 0.5f, 0.0f);         glclear(gl_color_buffer_bit);          triangle.draw();         triangle2.draw();          sdl_gl_swapwindow(window);         sdl_delay(1);     }      sdl_gl_deletecontext(context);     sdl_quit();     return 0; } 

mesh.h

#ifndef mesh_h #define mesh_h #include <gl/glew.h>  class mesh { private:     gluint ibo;     gluint vbo;     gluint vao;     float* vertices;     gluint* indices;      int sizevertices;     int sizeindices; public:     mesh(float* vertices, gluint* indices, int sizevertices, int sizeindices);     void draw(); };  #endif //mesh_h 

mesh.cpp

#include "mesh.h"  #define position 0 #define color 1  mesh::mesh(float* vertices, gluint* indices, int sizevertices, int sizeindices) {     this->vertices = vertices;     this->indices = indices;     this->sizevertices = sizevertices;     this->sizeindices = sizeindices;      glgenvertexarrays(1, &vao);     glgenbuffers(1, &vbo);     glgenbuffers(1, &ibo); }  void mesh::draw() {     glenablevertexattribarray(position);     glvertexattribpointer(position, 2, gl_float, gl_false,5*sizeof(float), 0);      glenablevertexattribarray(color);     glvertexattribpointer(color, 3, gl_float, gl_false, 5*sizeof(float), (void*)(2*sizeof(float)));      glbindvertexarray(vao);      glbindbuffer(gl_array_buffer, vbo);     glbufferdata(gl_array_buffer, sizevertices, vertices, gl_static_draw);      glbindbuffer(gl_element_array_buffer, ibo);     glbufferdata(gl_element_array_buffer, sizeindices, indices, gl_static_draw);      gldrawelements(gl_triangles, 3, gl_unsigned_int, 0);      //glbindvertexarray(0); if uncomment this, mesh not displayed } 

the calls glvertexattribpointer pointer refer vao , vbo bound @ time of calling. in code you're calling glvertexattribpointer before vao , vbo bound. first iteration round calls fail. without unbinding vao/vbo next iteration vao/vbo state happen (by circumstance) more or less right; you've swapped vao/vbo between 2 triangle instances.

update – fixed code

mesh::mesh(float* vertices, gluint* indices, int sizevertices, int sizeindices) {     this->vertices = vertices;     this->indices = indices;     this->sizevertices = sizevertices;     this->sizeindices = sizeindices;      glgenvertexarrays(1, &vao);     glgenbuffers(1, &vbo);     glgenbuffers(1, &ibo);      /* vaos contain array_buffers */     glbindvertexarray(vao);     glbindbuffer(gl_array_buffer, vbo);     glbufferdata(gl_array_buffer, sizevertices, vertices, gl_static_draw);      glenablevertexattribarray(position);     glvertexattribpointer(position, 2, gl_float, gl_false,5*sizeof(float), 0);      glenablevertexattribarray(color);     glvertexattribpointer(color, 3, gl_float, gl_false, 5*sizeof(float), (void*)(2*sizeof(float)));      glbindbuffer(gl_array_buffer, 0);     glbindvertexarray(vao);      /* element_array_buffers not contained in vaos */     glbindbuffer(gl_element_array_buffer, ibo);     glbufferdata(gl_element_array_buffer, sizeindices, indices, gl_static_draw);     glbindbuffer(gl_element_array_buffer, 0); }  void mesh::draw() {     /* vaos keep glvertexattribpointer bindings,      * it's sufficient bind vao;      * no need binding vbos (as long don't        want change pointers). */     glbindvertexarray(vao);     glbindbuffer(gl_element_array_buffer, ibo);      /* need bind element_array_buffer though */      gldrawelements(gl_triangles, 3, gl_unsigned_int, 0);      glbindbuffer(gl_element_array_buffer, 0);     glbindvertexarray(0); }