SFML - Opengl VAO 问题给我一个（1282）错误

Question

我在尝试在 SFML 中使用 VAO 时遇到错误，并且不确定它是 SFML 还是我自己的 opengl 代码

GLenum err = glewInit();
if (err != GLEW_OK)
{
    std::cout << "NOT WORKING" << std::endl;
}
    std::vector<sf::Vector3f> g_vertext_buffer_data;
g_vertex_buffer_data.push_back({ -1.0f, -1.0f, 0.0f });
g_vertex_buffer_data.push_back({1.0f, -1.0f, 0.0f});
g_vertex_buffer_data.push_back({ 0.0f, 1.0f, 0.0f });

const char* vertexShaderSource =
    "#version 330\n\
                             in vec4 position;\
                                                  void main(void){\                                                                                     gl_Position = position;\
                                                                                                         }";
// compile fragment shader source
const GLchar* fragmentShaderSource = 
    "#version 330\n\
                                    void main(void) {\
                out vec4 fragcolor;                                         fragcolor= vec4(1.0,1.0,1.0,1.0);\
                                                                                                     }";

/* Creating Shader */
this->programId = glCreateProgram();
this->vId = glCreateShader(GL_VERTEX_SHADER);
this->fId = glCreateShader(GL_FRAGMENT_SHADER);
/* Get Shader Size */
int vertexShaderLength = strlen(vertexShaderSource);
int fragmentShaderLength = strlen(fragmentShaderSource);

/* Loading and binding shader */
glShaderSource(this->vId, 1, &vertexShaderSource, NULL);
glShaderSource(this->fId, 1, &fragmentShaderSource, NULL);

/* Compile Shaders */
glCompileShader(vId);
glCompileShader(fId);
/* Attach Shaders */
glAttachShader(this->programId, this->vId);
glAttachShader(this->programId, this->fId);

/* Linkg program */
glLinkProgram(this->programId);
/* Use and bind attribute */
glUseProgram(this->programId);
this->positionId = glGetAttribLocation(this->programId, "position");
glUseProgram(0);
/* VAO Time */
glGenVertexArrays(1, &this->vaoId);
glBindVertexArray(this->vaoId);

/* VBO Time assigning to VAO */
glGenBuffers(1, &this->vboId);
glBindBuffer(GL_ARRAY_BUFFER, this->vboId);
glBufferData(GL_ARRAY_BUFFER, g_vertex_buffer_data.size() * sizeof(sf::Vector3f), &g_vertex_buffer_data[0], GL_STATIC_DRAW);
glEnableVertexAttribArray(this->positionId);
glVertexAttribPointer(this->positionId, 2, GL_FLOAT, GL_FALSE, sizeof(sf::Vector3f), 0);

/* Close out bindings */
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
  while(1)
  {
glUseProgram(this->programId);
glBindVertexArray(this->vaoId);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
glUseProgram(0);    
 gameWindow.glPushStates();
  }

我得到的错误代码是：opengl error in user code (1282)​

我已经更改了在 blBufferData() 中提出的 size() 问题，但问题仍然存在。

Answer 1

传递给glBufferData的大小至少有问题：

glBufferData(GL_ARRAY_BUFFER,
             sizeof(g_vertex_buffer_data) * sizeof(sf::Vector3f), 
             g_vertex_buffer_data[0], GL_STATIC_DRAW);

sizeof(g_vertex_buffer_data) 等于sizeof(std::vector<?>)，这是向量对象的大小，而不是包含的数据的大小。尝试使用

    glBufferData(GL_ARRAY_BUFFER,
             g_vertex_buffer_data.size() * sizeof(sf::Vector3f), 
             g_vertex_buffer_data[0], GL_STATIC_DRAW);

另一件事：在 OpenGL 3.3 Core Profile 中没有 gl_FragColor 变量。您必须定义一个输出变量。

下一步：您的顶点着色器似乎是空的。你必须写信给gl_Position，否则什么都不会显示。

Answer 2

glGetAttribLocation 的可能错误代码是：

GL_INVALID_OPERATION

没有固定值。尝试使用 gluErrorString() 获取错误字符串或查看标头中的 1282 个映射。

• 检查您的着色器是否正确编译？

• 检查您的着色器是否正确链接？

positionId 是什么类型的？所有对象 id 必须是 GLuint 类型。

顺便说一句，总是启用着色器编译链接错误检查，调试会提供更多信息。

我是这样做的（OpenGL-ES 2.0）：

    m_nVertexShader = glCreateShader(GL_VERTEX_SHADER);
    m_nPixelShader = glCreateShader(GL_FRAGMENT_SHADER);


    glShaderSource(m_nVertexShader, 1, &lpszVertexBuffer, NULL);
    glShaderSource(m_nPixelShader, 1, &lpszFragmentBuffer, NULL);

    glCompileShader(m_nVertexShader);

    int iIsOk = 0;

    glGetShaderiv(m_nVertexShader, GL_COMPILE_STATUS, &iIsOk);

    if(!iIsOk)
    {
        GLint infoLen = 0;

        glGetShaderiv(m_nVertexShader, GL_INFO_LOG_LENGTH, &infoLen);

        if(infoLen > 1)
        {
            char* infoLog = (char*)malloc(sizeof(char) * infoLen);

            glGetShaderInfoLog(m_nVertexShader, infoLen, NULL, infoLog);


            QMessageBox::warning(this, QString("Error"),
                                 QString(infoLog), QMessageBox::Yes | QMessageBox::Cancel, QMessageBox::Yes);

            free(infoLog);
        }

        glDeleteShader(m_nVertexShader);

        return;
    }

    glCompileShader(m_nPixelShader);

    glGetShaderiv(m_nPixelShader, GL_COMPILE_STATUS, &iIsOk);

    if(!iIsOk)
    {
        GLint infoLen = 0;

        glGetShaderiv(m_nPixelShader, GL_INFO_LOG_LENGTH, &infoLen);

        if(infoLen > 1)
        {
            char* infoLog = (char*)malloc(sizeof(char) * infoLen);

            glGetShaderInfoLog(m_nPixelShader, infoLen, NULL, infoLog);


            QMessageBox::warning(this, QString("Error"),
                                 QString(infoLog), QMessageBox::Yes | QMessageBox::Cancel, QMessageBox::Yes);

            free(infoLog);
        }

        glDeleteShader(m_nPixelShader);

        return;
    }

    m_nProgram = glCreateProgram();

    glAttachShader(m_nProgram, m_nVertexShader);
    glAttachShader(m_nProgram, m_nPixelShader);

    glBindAttribLocation(m_nProgram, 0, "rm_Vertex");

    glLinkProgram(m_nProgram);

    glGetProgramiv(m_nProgram, GL_LINK_STATUS, &iIsOk);

    // Fail to pass status validation
    if(!iIsOk)
    {
        GLint infoLen = 0;

        glGetProgramiv(m_nProgram, GL_INFO_LOG_LENGTH, &infoLen);

        if(infoLen > 1)
        {
            char* infoLog = (char*)malloc(sizeof(char) * infoLen);

            glGetProgramInfoLog(m_nProgram, infoLen, NULL, infoLog);


            QMessageBox::warning(this, QString("Error"),
                                 QString(infoLog), QMessageBox::Yes | QMessageBox::Cancel, QMessageBox::Yes);

            free(infoLog);
        }

        glDeleteProgram(m_nProgram);

        return;
    }

    glUseProgram(m_nProgram);

当您使用 GLSL 3.3 时，首先您必须通过调用指定片段渲染目标输出

glBindFragDataLocation(this->programId, 0, "fragcolor");

其次，你的片段着色器必须像

"#version 330
out vec4 fragcolor;

void main(void) {
     fragcolor= vec4(1.0,1.0,1.0,1.0); 
}

使用这种着色器的例子在OpenGL 3.3 + GLSL 1.5 Sample。