OpenGL：指定三角形的意外頂點位置

我在點數組中指定了一組頂點以繪製一個三角形，該三角形假定從窗口的頂部中間開始 - （+ 0.0f，+ 1.0f，+ 0.0f ） - 通過左下角 - （-1.0f，-1.0f，+ 0.0f） - 最後結束於窗口的右下角 - + 1.0f，-1.0f，+ 0.0f。但是，這個三角形沒有如上面那樣呈現，因爲它看起來像從窗口的頂部中間開始，然後到達左上角，最後在窗口中間右邊結束。我收錄了兩張截圖，以幫助我下面的問題描述。OpenGL：指定三角形的意外頂點位置

Unexpected rendering

Expected triangle hinted in red

#include <cstdio> 
#include <cstdlib> 

#include <GL/glew.h> 
#include <GLFW\glfw3.h> 

int main() { 
    // GLFW 
    if (!glfwInit()) { 
     fprintf(stderr, "ERROR: could not start GLFW3\n"); 
     return EXIT_FAILURE; 
    } 

    // Create window 
    GLFWwindow* window = glfwCreateWindow(800, 600, "OpenGL Test", NULL, NULL); 
    if (!window) { 
     fprintf(stderr, "ERROR: could not open window with GLFW3\n"); 
     glfwTerminate(); 
     return EXIT_FAILURE; 
    } 
    glfwMakeContextCurrent(window); 

    // GLEW 
    glewExperimental = GL_TRUE; 
    glewInit(); 

    // Get version info 
    const GLubyte* renderer = glGetString(GL_RENDERER); 
    const GLubyte* version = glGetString(GL_VERSION); 
    printf("Renderer: %s\n", renderer); 
    printf("Supported OpenGL version: %s\n", version); 

    glEnable(GL_DEPTH_TEST); 
    glDepthFunc(GL_LESS); 

    /* Put code here */ 

    // Vertices to be rendered 
    float points[] = { 
     +0.0f, +1.0f, +0.0f 
     -1.0f, -1.0f, +0.0f 
     +1.0f, -1.0f, +0.0f 
    }; 

    // Vertex buffer object 
    GLuint bufferId = 0; 
    glGenBuffers(1, &bufferId); 
    glBindBuffer(GL_ARRAY_BUFFER, bufferId); 
    glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW); 

    // Vertex attribute object 
    GLuint attributeId = 0; 
    glGenVertexArrays(1, &attributeId); 
    glBindVertexArray(attributeId); 
    glEnableVertexAttribArray(0); 
    glBindBuffer(GL_ARRAY_BUFFER, bufferId); 
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0); 

    // Shaders 
    const char* vertexShaderSource = 
     "#version 400\n" 
     "in vec3 position;" 
     "void main() {" 
     " gl_Position = vec4(position.x, position.y, position.z, 1.0);" 
     "}"; 

    const char* fragmentShaderSource = 
     "#version 400\n" 
     "out vec4 outColor;" 
     "void main() {" 
     " outColor = vec4 (0.0, 0.0, 1.0, 1.0);" 
     "}"; 

    // Compile shaders 
    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER); 
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL); 
    glCompileShader(vertexShader); 
    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); 
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL); 
    glCompileShader(fragmentShader); 
    // Link shaders 
    GLuint shaderPorgram = glCreateProgram(); 
    glAttachShader(shaderPorgram, fragmentShader); 
    glAttachShader(shaderPorgram, vertexShader); 
    glLinkProgram(shaderPorgram); 

    // Render loop 
    while (!glfwWindowShouldClose(window)) { 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
     glUseProgram(shaderPorgram); 
     glBindVertexArray(attributeId); 
     glDrawArrays(GL_TRIANGLES, 0, 3); 
     glfwPollEvents(); 
     glfwSwapBuffers(window); 
    } 

    glfwTerminate(); 
    return EXIT_SUCCESS; 
}

來源

2016-06-14 d03

哇，一個完整但短小的代碼？示例圖片的問題的簡要說明？不妨給我們免費的蛋糕！ –

缺少逗號。

float points[] = { 
    +0.0f, +1.0f, +0.0f 
    -1.0f, -1.0f, +0.0f 
    +1.0f, -1.0f, +0.0f 
};

應該是：

float points[] = { 
    +0.0f, +1.0f, +0.0f, 
    -1.0f, -1.0f, +0.0f, 
    +1.0f, -1.0f, +0.0f, 
};

最後一個逗號是沒有必要的，但它是允許的，我更喜歡它的風格問題。

來源

2016-06-14 00:11:14

OpenGL：指定三角形的意外頂點位置

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