C OpenGL glfw3 三角形不显示

Question

我有一个简单的 OpenGL C 应用程序，它试图在屏幕上绘制一个三角形。我已经成功地用 C++ 编写了类似的代码，没有任何问题。当我运行 C 程序时，它创建了 window，但没有显示任何内容。我的代码的主要部分如下。

void init()
{   
GLfloat vertices[] = {
    // Positions         
    0.0f,  0.5f, 0.0f, 0.0f,    // Top
    0.5f, -0.5f, 0.0f, 0.0f,    // Bottom Right
    -0.5f, -0.5f, 0.0f, 0.0f    // Bottom Left 
};

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

    GLuint buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    //glBindBuffer(GL_ARRAY_BUFFER, 0);

    GLuint program = loadShader("/shader1.vert", 
        "/shader1.frag");
    glUseProgram(program);

    GLuint vPosition = glGetAttribLocation(program, "VPosition");
    glEnableVertexAttribArray(vPosition);
    glVertexAttribPointer(vPosition, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));
    glBindVertexArray (vao);
}

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
    int w = 800;
    int h = 600;

    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
    //glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "glfw3", NULL, NULL);
    glfwMakeContextCurrent(window);
    glfwSetKeyCallback(window, key_callback);
    glViewport(0, 0, WIDTH, HEIGHT);

    init();

    while(!glfwWindowShouldClose(window))
    {
        glfwPollEvents();
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays( GL_TRIANGLES, 0, 3 );
        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}

使用顶点着色器

attribute vec4 vPosition;
void main()
{
    gl_Position = vPosition;
}

和片段着色器

void main()
{
    gl_FragColor = vec4( 1.0, 0.0, 0.0, 1.0 );
}

并加载着色器

char *readShader(char *filename)
{
FILE *fp;
char *content = NULL;

int count = 0;
if(filename != NULL)
{
    fp = fopen(filename, "rt");
    if(fp != NULL){
        fseek(fp, 0, SEEK_END);
        count = ftell(fp);
        rewind(fp);
        if (count > 0) {
            content = (char *)malloc(sizeof(char) * (count+1));
            count = fread(content,sizeof(char),count,fp);
            content[count] = '[=13=]';
        }
    }
    fclose(fp);
}
return content; 
}

GLuint loadShader(char *vertex_path, char *fragement_path)
{   
GLuint vertShader = glCreateShader(GL_VERTEX_SHADER);
GLuint fragShader = glCreateShader(GL_FRAGMENT_SHADER);

char *vertShaderStr = readShader(vertex_path);
char *fragShaderStr = readShader(fragement_path);

printf("Compiling vertex shader\n");
GLint vertLength = strlen(vertShaderStr);
glShaderSource(vertShader, 1, (const char **)&vertShaderStr, &vertLength);
glCompileShader(vertShader);

//Check vertex shader
GLint vertSuccess;
glGetShaderiv(vertShader, GL_COMPILE_STATUS, &vertSuccess);
if(vertSuccess == GL_FALSE) {
    char log[1024];
    glGetShaderInfoLog(vertShader, sizeof(log), 0, log);
    printf("Vertex shader compile info: \n %s \n", log);
    glDeleteShader(vertShader);
    return 1;
}


printf("Compiling fragment shader\n");
GLint fragLength = strlen(fragShaderStr);
glShaderSource(fragShader, 1, (const char **)&fragShaderStr, &fragLength);
glCompileShader(fragShader);

//Check fragment shader
GLint fragSuccess;
glGetShaderiv(fragShader, GL_COMPILE_STATUS, &fragSuccess);
if(vertSuccess == GL_FALSE) {
    char log[1024];
    glGetShaderInfoLog(vertShader, sizeof(log), 0, log);
    printf("Fragment shader compile info: \n %s \n", log);
    glDeleteShader(fragShader);
    return 1;
}

printf("Linking program\n");
GLuint program = glCreateProgram();
glAttachShader(program, vertShader);
glAttachShader(program, fragShader);
glLinkProgram(program);

GLint programSuccess;
glGetProgramiv(program, GL_LINK_STATUS, &programSuccess);
if(programSuccess == GL_FALSE) {
    char log[1024];
    glGetProgramInfoLog(program, sizeof(log), 0, log);
    printf("shader link info: \n %s \n", log);
    glDeleteProgram(program);
    return 1;
}

//printf("%s", vertShaderStr);
//printf("%s", fragShaderStr);
return program;
}

Answer 1

这里： GLfloat 顶点[] = { // 位置
0.0f, 0.5f, 0.0f, 0.0f, // 顶部 0.5f, -0.5f, 0.0f, 0.0f, // 右下角 -0.5f, -0.5f, 0.0f, 0.0f // 左下角 }

您指定 0 作为所有顶点的 w 坐标。你真的要在这里放1，否则你的顶点无限远。

请注意，通常所有顶点的输入 w`坐标始终为 1，将其显式存储在数组中会浪费内存和带宽。如果未指定，GL 会自动将向量的第四个分量扩展为 1，因此您可以简单地使用

GLfloat vertices[] = {
    // Positions         
    0.0f,  0.5f, 0.0f,    // Top
    0.5f, -0.5f, 0.0f,    // Bottom Right
    -0.5f, -0.5f, 0.0f,   // Bottom Left 
};
// ...
glVertexAttribPointer(vPosition, 3 GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));

无需完全改变着色器中的 attribute vec4。

我还觉得可疑的是您从不加载 GL 函数指针。我没有粘贴你包含的内容 headers，但绝对不能在所有平台上运行。

C OpenGL glfw3 三角形不显示

C OpenGL glfw3 triangle not displaying

c

opengl

graphics

glfw