Question

我在点数组中指定了一组顶点来绘制一个三角形，该三角形应该从窗口的顶部中间开始 - （+ 0.0f，+ 1.0f，+ 0.0f） - 穿过左下角 - （-1.0f，-1.0f，+ 0.0f） - 最后在窗口的右下角结束 - + 1.0f，-1.0f，+ 0.0f。但是，三角形不会像上面那样呈现，因为它看起来像是从窗口的顶部中间开始，然后转到左上角，最后到达窗口中间。我在下面提供了两个屏幕截图来帮助解决我的问题。

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;
}

Answer 1

缺少逗号。

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

应该是：

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

最后一个逗号不是必需的，但它是允许的，我更喜欢它作为一种风格问题。

OpenGL：指定三角形的意外顶点位置

1 个答案: