c++ - 我尝试运行 OpenGl，但 GLUT 屏幕只是呈现白屏？

Question

我刚刚尝试运行从 2 个顶点绘制一条线的 Bresenham 函数，但只出现 GLUT 的白屏，根本没有线。这是我的源代码，有人可以帮助我吗？

#include <math.h>
#include <windows.h>
#include <GL/glut.h>
#include <GL/gl.h>

void init(void)
{
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(0.0, 500.0, 0.0, 500.0);
}
void Bresenham(int x1, int y1, int x2, int y2) {
    int Dx = abs(x2 - x1);
    int Dy = abs(y2 - y1);
    int p = 2 * Dy - Dx;
    int c1 = 2 * Dy;
    int c2 = 2 * (Dy - Dx);
    int x = x1;
    int y = y1;
    int x_unit = 1, y_unit = 1;
    glVertex2d(x, y);
    while (x != x2) {
        if (p<0) p += c1;
        else {
            p += c2;
            y += y_unit;
        }
        x += x_unit;
        glVertex2d(x, y);
    }
}
void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_POLYGON);
    Bresenham(50, 150, 300, 200);
    glEnd();
    glFlush();
}
int main(int iArgc, char** cppArgv) {
    glutInit(&iArgc, cppArgv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(600, 600);
    glutInitWindowPosition(50, 50);
    glutCreateWindow("Line");
    init();
    int x1=50, y1=150, x2=300, y2=200;
    glutDisplayFunc(display); 
    glutMainLoop();
    return EXIT_SUCCESS;
}

Answer 1

确保您的背景颜色与您的绘图颜色不匹配。有点难看白底白字 :)

在我的机器上用红色画线:

#include <GL/glut.h>

void Bresenham(int x1, int y1, int x2, int y2)
{
    int Dx = abs(x2 - x1);
    int Dy = abs(y2 - y1);
    int p = 2 * Dy - Dx;
    int c1 = 2 * Dy;
    int c2 = 2 * (Dy - Dx);
    int x = x1;
    int y = y1;
    int x_unit = 1, y_unit = 1;
    glVertex2d(x, y);
    while (x != x2)
    {
        if (p<0)
            p += c1;
        else
        {
            p += c2;
            y += y_unit;
        }
        x += x_unit;
        glVertex2d(x, y);
    }
}

void display(void)
{
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, 500.0, 0.0, 500.0, -1, 1);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBegin(GL_POLYGON);
    glColor3ub( 255, 0, 0 );
    Bresenham(50, 150, 300, 200);
    glEnd();

    glutSwapBuffers();
}

int main(int argc, char** argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(600, 600);
    glutCreateWindow("Line");
    glutDisplayFunc(display); 
    glutMainLoop();
    return 0;
}