c++ - 在OpenGL中实现VBO，窗口保持黑色

Question

我试图用我的 VBO/OpenGL 练习解决一个错误，但几个小时(几天)后，我找不到问题所在。

问题是窗口保持黑色，未(正确)绘制立方体。

-

OpenGL 上下文似乎是为 OpenGL 3.2 正确创建的

顶点着色器:

#version 150 core
uniform mat4 RotationMatrix;
uniform mat4 ProjectionMatrix;

in vec3 in_Position;

void main(void)
{
    gl_Position = ProjectionMatrix * RotationMatrix * vec4(in_Position, 1.0);
}

VBO初始化:

// <-- Create OpenGL 3.2 context
// <-- Load Shaders
// <-- Set ClearColor, clearDepth, DepthFUnc, enable Depth
// <-- Set Viewport, init projection and modelview matrix.
float positionData[] = 
{
    -0.5f, 0.5f, -0.5f,
    0.5f, 0.5f, -0.5f,
    0.5f, -0.5f, -0.5f,
    -0.5f, -0.5f, -0.5f,
    -0.5f, 0.5f, 0.5f,
    0.5f, 0.5f, 0.5f,
    0.5f, -0.5f, 0.5f,
    -0.5f, -0.5f, 0.5f,
};

GLuint indexes[] = 
{
    0, 1, 2, 0, 2, 3,
    4, 5, 6, 4, 6, 7, 
    0, 3, 7, 0, 7, 4, 
    1, 5, 6, 1, 6, 2, 
    0, 4, 5, 0, 5, 1, 
    2, 3, 7, 2, 7, 6
};
glGenBuffers(2, vboHandles);
glBindBuffer( GL_ARRAY_BUFFER, vboHandles[0]);
glBufferData(GL_ARRAY_BUFFER, 24*sizeof(float), positionData, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboHandles[1]); 
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 36*sizeof(GLuint), 
    indexes, GL_STATIC_DRAW);

在OpenGL绘制函数中:

//<--Clear buffer, set Uniform variables for projection and modelview

glBindBuffer(GL_ARRAY_BUFFER, vboHandles[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboHandles[1]);

glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, NULL);

//<-- Flush Opengl and swap buffers

正确/不正确

已编辑:片段着色器:

#version 150 core
out vec4 out_Color;
void main(void){
    out_Color = vec4(1.0, 0.0, 0.0, 1.0f);
}

编辑 2:添加上下文创建

SDL_Window* window;
SDL_GLContext context;
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    return 0;
}
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES,  4);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,  1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE,  16);

if ((window = SDL_CreateWindow( "Practica 4 and lot of stuff for the final prictice", 
    SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
    800, 600, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN)) == NULL)
{
    SDL_Quit();
    return 0;
}
if (NULL== (context = SDL_GL_CreateContext(window)))
{
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 0;
}

glewExperimental = GL_TRUE;
GLuint glewStatus = glewInit();
if (glewStatus != GLEW_OK)
{
    cout << "Error" << endl;
}

Answer 1

在这里工作得很好:

#include <GL/glew.h>
#include <GL/freeglut.h>

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
using namespace glm;

#include <iostream>
using namespace std;


struct Program
{
    static GLuint Load( const char* vert, const char* geom, const char* frag )
    {
        GLuint prog = glCreateProgram();
        if( vert ) AttachShader( prog, GL_VERTEX_SHADER, vert );
        if( geom ) AttachShader( prog, GL_GEOMETRY_SHADER, geom );
        if( frag ) AttachShader( prog, GL_FRAGMENT_SHADER, frag );
        glLinkProgram( prog );
        CheckStatus( prog );
        return prog;
    }

private:
    static void CheckStatus( GLuint obj )
    {
        GLint status = GL_FALSE;
        if( glIsShader(obj) ) glGetShaderiv( obj, GL_COMPILE_STATUS, &status );
        if( glIsProgram(obj) ) glGetProgramiv( obj, GL_LINK_STATUS, &status );
        if( status == GL_TRUE ) return;
        GLchar log[ 1 << 15 ] = { 0 };
        if( glIsShader(obj) ) glGetShaderInfoLog( obj, sizeof(log), NULL, log );
        if( glIsProgram(obj) ) glGetProgramInfoLog( obj, sizeof(log), NULL, log );
        std::cerr << log << std::endl;
        exit( -1 );
    }

    static void AttachShader( GLuint program, GLenum type, const char* src )
    {
        GLuint shader = glCreateShader( type );
        glShaderSource( shader, 1, &src, NULL );
        glCompileShader( shader );
        CheckStatus( shader );
        glAttachShader( program, shader );
        glDeleteShader( shader );
    }
};

#define GLSL(version, shader) "#version " #version "\n" #shader

const char* vert = GLSL
(
    150 core,
    uniform mat4 RotationMatrix;
    uniform mat4 ProjectionMatrix;

    in vec3 in_Position;

    void main(void)
    {
        gl_Position = ProjectionMatrix * RotationMatrix * vec4(in_Position, 1.0);
    }
);

const char* frag = GLSL
(
    150 core,
    out vec4 out_Color;
    void main(void){
        out_Color = vec4(1.0, 0.0, 0.0, 1.0f);
    }
);

GLuint vbo = 0;
GLuint ibo = 0;
void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    double w = glutGet( GLUT_WINDOW_WIDTH );
    double h = glutGet( GLUT_WINDOW_HEIGHT );
    double ar = w / h;
    mat4 projection = glm::ortho< float >( -1 * ar, 1 * ar, -1.0, 1.0, -1.0, 1.0 );

    mat4 modelview = mat4( 1.0 );

    // prepare to render
    static GLuint prog = Program::Load( vert, NULL, frag );
    glUseProgram( prog );

    GLint proj = glGetUniformLocation( prog, "ProjectionMatrix" );
    glUniformMatrix4fv( proj, 1, GL_FALSE, glm::value_ptr( projection ) );

    GLint model = glGetUniformLocation( prog, "RotationMatrix" );
    glUniformMatrix4fv( model, 1, GL_FALSE, glm::value_ptr( modelview ) );

    float positionData[] = 
    {
        -0.5f, 0.5f, -0.5f,
        0.5f, 0.5f, -0.5f,
        0.5f, -0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,
        -0.5f, 0.5f, 0.5f,
        0.5f, 0.5f, 0.5f,
        0.5f, -0.5f, 0.5f,
        -0.5f, -0.5f, 0.5f,
    };
    glBindBuffer( GL_ARRAY_BUFFER, vbo );
    glBufferData( GL_ARRAY_BUFFER, sizeof( positionData ), positionData, GL_STREAM_DRAW );

    GLuint indexes[] = 
    {
        0, 1, 2, 0, 2, 3,
        4, 5, 6, 4, 6, 7, 
        0, 3, 7, 0, 7, 4, 
        1, 5, 6, 1, 6, 2, 
        0, 4, 5, 0, 5, 1, 
        2, 3, 7, 2, 7, 6
    };
    glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, ibo ); 
    glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( indexes ), indexes, GL_STREAM_DRAW );

    GLint pos = glGetAttribLocation( prog, "in_Position" );
    glVertexAttribPointer( pos, 3, GL_FLOAT, GL_FALSE, 0, 0 );
    glEnableVertexAttribArray( pos );

    glDrawElements( GL_TRIANGLES, sizeof( indexes ) / sizeof( GLuint ), GL_UNSIGNED_INT, 0 );

    glutSwapBuffers();
}

int main(int argc, char **argv)
{
    glutInit( &argc, argv );
    glutInitContextVersion( 3, 2 );
    glutInitContextProfile( GLUT_CORE_PROFILE );
    glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
    glutInitWindowSize( 600, 600 );
    glutCreateWindow( "GLUT" );

    glewExperimental = GL_TRUE;
    glewInit();

    GLuint vao = 0;
    glGenVertexArrays( 1, &vao );
    glBindVertexArray( vao );

    glGenBuffers( 1, &vbo );
    glGenBuffers( 1, &ibo );

    glutDisplayFunc( display );
    glutMainLoop();
    return 0;
}