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我正在尝试使用着色器、缓冲区等编写一个基本的 OpenGL 3.3 程序来绘制一个立方体。问题是没有绘制立方体。抱歉这么多代码，但我觉得错误可能在任何地方，因为对我来说这一切似乎都是正确的：显示函数正在循环，着色器被编译，矩阵被传递给着色器。我怀疑剔除可能有问题。请看一下。这是代码（我正在使用freeglut，首先调用init（），然后显示循环运行）：

初始化代码：

struct ProgramData
{
    GLuint theProgram;
    GLuint iModel;
    GLuint iView;
    GLuint iProjection;
};

ProgramData shaderProgram;

ProgramData LoadProgram(const std::string &strVertexShader, 
                        const std::string &strFragmentShader)
{
    std::vector<GLuint> shaderList;

    shaderList.push_back(LoadShader(GL_VERTEX_SHADER, strVertexShader));
    shaderList.push_back(LoadShader(GL_FRAGMENT_SHADER, strFragmentShader));

    ProgramData data;
    data.theProgram = CreateProgram(shaderList);
    data.iModel = glGetUniformLocation(data.theProgram, "mModel");
    data.iView = glGetUniformLocation(data.theProgram, "mView");
    data.iProjection = glGetUniformLocation(data.theProgram, "mProjection");

    return data;
}

float cube_vertices[] = {
    -1.0f, -1.0f,  1.0f,
     1.0f, -1.0f,  1.0f,
     1.0f,  1.0f,  1.0f,
    -1.0f,  1.0f,  1.0f,
    -1.0f, -1.0f, -1.0f,
     1.0f, -1.0f, -1.0f,
     1.0f,  1.0f, -1.0f,
    -1.0f,  1.0f, -1.0f,

    GREEN_COLOR,
    BLUE_COLOR,
    RED_COLOR,
    BROWN_COLOR,

    GREEN_COLOR,
    BLUE_COLOR,
    RED_COLOR,
    BROWN_COLOR,
};

GLubyte cube_elements[] = {
     0,1,2, 2,3,0,   
     0,3,4, 4,5,0,
     0,5,6, 6,1,0,
     1,6,7, 7,2,1,
     7,4,3, 3,2,7,
     4,7,6, 6,5,4
};

void InitializeProgram()
{

    //initialize vertex buffer
    glGenBuffers(1, &vertex_buffer_obj);
    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_obj);
    glBufferData(GL_ARRAY_BUFFER, sizeof(cube_vertices), 
                   cube_vertices, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

    //initialize index buffer
    glGenBuffers(1, &index_buffer_obj);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer_obj);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_elements), 
                           cube_elements, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

    shaderProgram = LoadProgram("shader.vert", "shader.frag");
}

void init()
{
    InitializeProgram();

    int numberOfVertices = 8;
    size_t color_data_offset = sizeof(float) * 3 * numberOfVertices;

    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);

    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_obj);
    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, 
                          (void*)color_data_offset);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer_obj);
    glBindVertexArray(0);


    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
    glFrontFace(GL_CW);

    glEnable(GL_DEPTH_TEST);
    glDepthMask(GL_TRUE);
    glDepthFunc(GL_LEQUAL);
    glDepthRange(0.0f, 1.0f);

}

顶点着色器：

#version 330

layout (location = 0) in vec3 inPosition;
layout (location = 1) in vec3 color;

uniform mat4 mProjection;
uniform mat4 mView;
uniform mat4 mModel;

smooth out vec3 theColor;

void main()
{
    gl_Position = mProjection * mView * mModel * vec4(inPosition, 1);
    theColor = color;
}

片段着色器：

#version 330

smooth in vec3 theColor;
out vec4 outputColor;

void main()
{
    outputColor = vec4(theColor, 1);
}

绘制代码：

glm::vec3 cam_pos(3, 2, 3);
void display()
{

glClearColor(0.3f, 0.3f, 0.3f, 1.0f);
glClearDepth(1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glUseProgram(shaderProgram.theProgram);

glm::mat4 model_matrix = glm::translate(glm::vec3(0, 0, 0));
glm::mat4 view_matrix = glm::lookAt(cam_pos, 
                         glm::vec3(0, 0, 0), glm::vec3(0, 0, 1));
glm::mat4 proj_matrix = glm::perspective(45.0f, 1.0f, 1.0f, 100.0f);

glUniformMatrix4fv(shaderProgram.iProjection, 1, 
                       GL_FALSE, glm::value_ptr(proj_matrix));
glUniformMatrix4fv(shaderProgram.iView, 1, 
                       GL_FALSE, glm::value_ptr(view_matrix));
glUniformMatrix4fv(shaderProgram.iModel, 1, 
                       GL_FALSE, glm::value_ptr(model_matrix));

glBindVertexArray(vao);
int size;  glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, 
                                      GL_BUFFER_SIZE, &size);
glDrawElements(GL_TRIANGLES, size / sizeof(GLubyte), GL_UNSIGNED_SHORT, 0);

glBindVertexArray(0);
glUseProgram(0);

    glutSwapBuffers();
    glutPostRedisplay();
}

UPD：在 init 方法中计算颜色的偏移量时应该 sizeof(float) * 3 * numberOfVertices代替 sizeof(GLubyte) * 3 * numberOfVertices存储为浮点数。渲染问题未解决。

已解决：谢谢您的帮助。请看下面我的回答。

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2 回答 2

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我在浏览您的代码时发现的事情是您的顶点着色器中的以下行：

gl_Position = mProjection * mView * mModel * vec4(inPosition, 0);

那0应该真的是一个1.0。

于 2013-10-26T17:49:35.493 回答
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在 display() 函数中

glDrawElements(GL_TRIANGLES, size / sizeof(GLubyte), GL_UNSIGNED_SHORT, 0);

应该改为

glDrawElements(GL_TRIANGLES, size / sizeof(GLubyte), GL_UNSIGNED_BYTE, 0);

并在 init()

glFrontFace(GL_CW);

至

glFrontFace(GL_CCW);

所以问题是我传递给OpenGL的数据不正确。索引数组是 GLUbyte （每个数组元素 1 字节大小），但我出于某种原因决定它是 GLushort （2 字节）。

编辑：没关系，但是向上向量（生成相机矩阵时）应该不是glm::vec3(0, 0, 1)但是glm::vec3(0, 1, 0)

于 2013-10-27T00:01:38.903 回答