OpenGL绘制满屏

Question

我正在尝试完整地绘制一个 2D 足球场 window。但是，它在左侧和右侧出现黑条：

这是我的代码：

#include <OpenGL/gl.h> // include GLEW and new version of GL on Windows
#include <GLFW/glfw3.h> // GLFW helper library
#include <stdio.h>
#include <math.h>

void Soccer_Field();

int main() {
    // start GL context and O/S window using the GLFW helper library
    if (!glfwInit()) {
        fprintf(stderr, "ERROR: could not start GLFW3\n");
        return 1;
    }

    // uncomment these lines if on Apple OS X
    /*glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
     glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);*/

    GLFWwindow* window = glfwCreateWindow(640, 480, "Soccer field", NULL, NULL);
    if (!window) {
        fprintf(stderr, "ERROR: could not open window with GLFW3\n");
        glfwTerminate();
        return 1;
    }
    glfwMakeContextCurrent(window);

    // get version info
    const GLubyte* renderer = glGetString(GL_RENDERER); // get renderer string
    const GLubyte* version = glGetString(GL_VERSION); // version as a string
    printf("Renderer: %s\n", renderer);
    printf("OpenGL version supported %s\n", version);

    /* OTHER STUFF GOES HERE NEXT */
    while(!glfwWindowShouldClose(window)) {
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0.0, 1, 0.0, 1, -1.0, 1.0);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();

       Soccer_Field();

        // update other events like input handling
        glfwPollEvents();
        // put the stuff we've been drawing onto the display
        glfwSwapBuffers(window);
    }

    // close GL context and any other GLFW resources
    glfwTerminate();
    return 0;
}

void Soccer_Field (void)
{
    float x, y, ang, radius = 0.05;     // Not sure what the radius of the center circle should be?

    static float RAD_DEG = 57.296;

    glBegin (GL_QUADS);
    glColor3f  (0.20, 0.60, 0.20);                           // GreenYard
    glVertex2f (0.10, 0.10); glVertex2f (0.90, 0.10);
    glVertex2f (0.90, 0.90); glVertex2f (0.10, 0.90);
    glColor3f  (1.0, 1.0, 1.0);
    glVertex2f (0.90, 0.35); glVertex2f (0.83, 0.35);        // Inner White Quad - Right
    glVertex2f (0.83, 0.65); glVertex2f (0.90, 0.65);
    glVertex2f (0.10, 0.35); glVertex2f (0.17, 0.35);        // Inner White Quad - Left
    glVertex2f (0.17, 0.65); glVertex2f (0.10, 0.65);
    glEnd ();

    glColor3f (0.0, 0.0, 0.0);                                  // Change color to black

    glBegin (GL_LINES);
    glVertex2f (0.50, 0.10); glVertex2f (0.50, 0.90);        // Mid Line

    // Left side of the Ground
    glVertex2f (0.25, 0.25); glVertex2f (0.25, 0.75);        // Goal keeper front line
    glVertex2f (0.10, 0.75); glVertex2f (0.25, 0.75);        // Goal keeper left line
    glVertex2f (0.10, 0.25); glVertex2f (0.25, 0.25);        // Goal keeper right line

    // Right Side of the Ground
    glVertex2f (0.75, 0.25); glVertex2f (0.75, 0.75);        // Goal keeper front line
    glVertex2f (0.75, 0.25); glVertex2f (0.90, 0.25);        // Goal keeper left  Line
    glVertex2f (0.75, 0.75); glVertex2f (0.90, 0.75);        // Goal keeper right line
    glEnd ();

    glBegin (GL_LINE_LOOP);                                     // Circle at center of field
    for (ang = 0.0; ang < 360.0; ang += 10.0)  {
        x = radius * cos(ang/RAD_DEG) + 1.0;
        y = radius * sin(ang/RAD_DEG) + 0.5;
        glVertex2f (x/2.0, y);
    }
    glEnd ();
}

我该如何解决这个问题？我已尝试设置视口和其他设置，但无法正常工作。

希望有人让我直截了当。

谢谢

Answer 1

投影矩阵描述了从场景的 3D 点到视口的 2D 点的映射。投影矩阵从viewspace变换到clipspace，clipspace中的坐标变换为范围为(-1,-1)的归一化设备坐标(NDC) , -1) 到 (1, 1, 1) 除以剪辑坐标的 w 分量。
在正交投影中，眼睛中的坐标 space 线性映射到归一化设备坐标。

正射投影矩阵由glOrtho定义。使用此功能，您可以定义场景的视野。

由于你所有的几何图形都在(0.1, 0.1) 到(0.9, 0.9) 的范围内，你必须将其更改为：

GLdouble left   = 0.1;
GLdouble right  = 0.9; 
GLdouble bottom = 0.1;
GLdouble top    = 0.9; 
glOrtho(left, right, bottom, top, -1.0, 1.0);

第二种可能性是通过模型视图矩阵缩放几何体。你必须缩放 (glScale) the geometry from [(0.1, 0.1), (0.9, 0.9)] to the range which which is set up by the orthographic projection [(0.0, 0.0), (1.0, 1.0)]. Note, in this case you have to "re-center" the geometry (glTranslate):

glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

GLdouble scaleX = (1.0 - 0.0) / (0.9 - 0.1);
GLdouble scaleY = (1.0 - 0.0) / (0.9 - 0.1); 
glScaled( scaleX, scaleY, 1.0 );
glTranslated( -0.1, -0.1, 0.0 );

OpenGL绘制满屏

OpenGL draw full of screen

c++

opengl

orthographic