OpenGL 3.3 2D 渲染:VAO 配置不正确

添加VAO后，我似乎无法让这个OpenGL程序渲染四边形。

假设程序正确初始化且没有错误，以下是填充 VAO 的代码。

float quad[] = 
    {
        //verts        colors
        32.0f,  0.0f, 1.0f, 0.0f, 0.0f, // Top-left
        32.0f,  32.0f, 0.0f, 1.0f, 0.0f, // Top-right
        0.0f, 32.0f, 0.0f, 0.0f, 1.0f, // Bottom-right
        0.0f, 0.0f, 1.0f, 1.0f, 1.0f  // Bottom-left
    };
float textureCoords[] = 
    {
        0.0f, 0.0f, //x
        0.5f, 0.0f, //w
        0.5f, 0.5f, //y
        0.0f, 0.5f  //h
    };
float elements[] =
    {
        0,1,2,
        2,3,0
    };
//loadShaders compiles and links both shaders
GLuint shaders = loadShaders("vertexShader.c", "fragmentShader.c");
GLuint VAO, VBO[2], EBO;

glGenVertexArrays(1, &VAO);
glGenBuffers(2, VBO);
glGenBuffers(1, &EBO);
//bind VAO
glBindVertexArray(VAO);
glUseProgram(shaders);
//quad and color data
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(quad), quad, GL_STATIC_DRAW);
GLint quadAttrib = glGetAttribLocation(shaders, "quad");
glEnableVertexAttribArray(quadAttrib);//target 'quad' in shader
glVertexAttribPointer(quadAttrib, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), 0);
//color data
GLint colorAttrib = glGetAttribLocation(shaders, "color");
glEnableVertexAttribArray(colorAttrib);//target 'color' in shader
glVertexAttribPointer(colorAttrib, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (void*)(2 * sizeof(GLfloat)));
//UV data
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(textureCoords), textureCoords, GL_STATIC_DRAW);
GLint uvAttrib = glGetAttribLocation(shaders, "uvCoords");//target 'uvCoords' in shaders 
glEnableVertexAttribArray(uvAttrib);
glVertexAttribPointer(uvAttrib, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), 0);

//TEXTURES
//laod and use textures
GLuint textures[2];
glGenTextures(2, textures);

int texWidth, texHeigth;
unsigned char *image;
//activate texture 0
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textures[0]);
image = SOIL_load_image("atlas.png", &texWidth, &texHeigth, 0, SOIL_LOAD_RGB);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, texWidth, texHeigth, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
SOIL_free_image_data(image);
glUniform1i(glGetUniformLocation(shaders, "img1"), 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

//element buffer data
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);
//UNIFORMS
//projection matrix
GLint projectionUniform = glGetUniformLocation(shaders, "projection");
glm::mat4 orthoProjection = glm::ortho( 0.0f, static_cast<float>(480), 0.0f, static_cast<float>(272));
glUniformMatrix4fv(projectionUniform, 1, GL_FALSE, glm::value_ptr(orthoProjection));
//model view projection
GLint modelViewUniform = glGetUniformLocation(shaders, "modelView");

//unbind VAO and current shader, the VAO remembers the bound shader
glBindVertexArray(0);
glUseProgram(0);

我假设VAO现在已经跟踪了以下内容：

• 着色器中的四边形缓冲区 'VBO[0]' 及其对应的属性指针 'quadAttrib' 到 "quad">
• 着色器中的颜色缓冲区"相同的 VBO[0]"及其相应的属性指针"colorAttrib"到"color">
• UV 缓冲区 'VBO[1]' 及其对应的属性指针 'uvAttrib' 到 'uvCoords' 在着色器中
• 当前纹理单元 (0( 对应于加载的纹理和绑定到片段着色器中的"img1"及其参数
绑定到
• GL_ELEMENT_ARRAY_BUFFER的EBO
• 投影矩阵及其均匀
• 模型矩阵的处理程序
绑定
• VAO 时正在使用的着色器程序？不确定，我仍然明确使用程序中唯一的着色器程序

稍后在主循环中，如果我尝试执行以下操作，则不会绘制任何内容：

    // Clear the screen to black
    glClearColor(0.2f, 0.0f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    //draw the quad within this VAO
    glBindVertexArray(VAO);
glUseProgram(shaders);
    glm::mat4 model;
    model = glm::translate(glm::mat4(1.0f), glm::vec3(newTransX, newTransY, newTransZ));
    model = glm::scale(model, glm::vec3(newScale));
    model = glm::rotate(
        model,
        (GLfloat)clock()  / (GLfloat)CLOCKS_PER_SEC * 10000.0f,
        glm::vec3(0.0f, 0.0f, 1.0f)
    );      
// upload the uniform matrix, modelViewUniform should be already linked to the shader uniform through the VAO
    glUniformMatrix4fv(modelViewUniform, 1, GL_FALSE, glm::value_ptr(model)); 

    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
    SDL_GL_SwapWindow(window);

顶点着色器：

    #version 330
in vec2 quad;
in vec3 color;
in vec2 uvCoords;
out vec3 Color;
out vec2 UVCoords;

uniform mat4 modelView;
uniform mat4 projection;
void main()
{
    Color = color;
    UVCoords = uvCoords;
    gl_Position = projection * modelView * vec4(quad, 0.0f, 1.0f);
}

片段着色器：

    #version 330
in vec3 Color;//not in use, simple pipeline test
in vec2 UVCoords;
out vec4 outColor;
uniform sampler2D img1;

void main()
{
    vec4 finalTexture = texture(img1, UVCoords);
    outColor = finalTexture;
} 

我做错了什么？我知道模型视图和投影矩阵中的值是正确的，因为如果我从不使用 VAO，程序就可以工作。

我是否假设VAO记得的比实际记得的多？如果不是，我做错了什么？