Question

我想在整个窗口中绘制一个2D足球场。但是，它会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？我试图设置视口和其他东西，但我无法让它工作。

希望有人能直截了当地接受我。

由于

Answer 1

投影矩阵描述了从场景的3D点到视口的2D点的映射。投影矩阵从视图空间转换到剪辑空间，剪辑空间中的坐标转换为范围（-1，-1，-1）到（1,1,1）范围内的规范化设备坐标（NDC）通过用剪辑坐标的w分量除以。
在Orthographic Projection中，眼睛空间中的坐标线性映射到标准化设备坐标。

ortogrpahic投影矩阵由glOrtho定义。使用此功能，您可以定义场景的视野。

由于您的所有几何体都在（0.1,0.1）到（0.9,0.9）的范围内，因此您必须将其更改为：

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。您必须将[（0.1,0.1），（0.9,0.9）]的几何（glScale）缩放到由正投影[（0.0,0.0），（1.0,1.0）设置的范围内）]。请注意，在这种情况下，您必须“重新居中”几何体（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绘制完整的屏幕

1 个答案: