Question

我正在尝试使用绘画中的工具绘制一个形状，在此处拖动它，当您释放鼠标时，它将绘制形状。

目前我的程序所做的是，如果你点击它会产生橡皮筋来显示形状的样子，但是当你释放鼠标点击时什么也没有画出来。

相关代码如下：

// this function draws the list of objects
void drawList() {
    glClear(GL_COLOR_BUFFER_BIT); // Clear display window.
    if (list[numObj].t==1){
        glBegin(GL_LINE_LOOP);
        glVertex2i(list[numObj].x1, list[numObj].y1);
        glVertex2i(list[numObj].x1, list[numObj].y2);
        glVertex2i(list[numObj].x2, list[numObj].y2);
        glVertex2i(list[numObj].x2, list[numObj].y1);
        glEnd();
    }
    glFlush();
}

void mouseDraw(GLint button, GLint action, GLint xMouse, GLint yMouse) {
    if (type == 1){
        if (button == GLUT_LEFT_BUTTON) {
            if (action == GLUT_DOWN && button != GLUT_RIGHT_BUTTON && numObj < MaxNumObj -1) {
                list[numObj].x1 = xMouse;
                list[numObj].y1 = yMouse;
                list[numObj].x2 = xMouse;
                list[numObj].y2 = yMouse;
                list[numObj].t = type;
                list[numObj].s = 2;
                list[numObj].r = red;
                list[numObj].g = green;
                list[numObj].b = blue;
                glutPostRedisplay();

            } else if (action == GLUT_UP && button != GLUT_RIGHT_BUTTON) {
                list[numObj].x2 = xMouse;
                list[numObj].y2 = yMouse;
                list[numObj].s = style;
                numObj++;
                glutPostRedisplay();
            }
        }
    }
}

// this function takes the mouse position while moving mouse, use this for intermediate drawing
void Motion(GLint x, GLint y) {
    // add the (x, y) coordinates of the second point to the intermediate rectangle
    list[numObj].x2 = x;
    list[numObj].y2 = y;
    // redisplay the object list after the above insertion. It will give a rubber band effect

    glutPostRedisplay ( );
}

相关主要代码：

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(100, 100);
glutInitWindowSize(winWidth, winHeight);
glutCreateWindow("SimpleDraw Example");

init();

// register call back funtions
glutDisplayFunc(drawList);
glutReshapeFunc(winReshapeFcn);
glutMouseFunc(mouseDraw);
glutMotionFunc(Motion);

//add right click menu
glutAttachMenu(GLUT_RIGHT_BUTTON);

glutMainLoop();

请忽略.s .t和东西，唯一相关的东西应该是x和ys。

以下是一些显示我当前结果和预期结果的GIF：

我目前的计划是

我想要它做什么

Answer 1

您必须从第一个到最后一个绘制存储在list中的所有矩形：

void drawList() {

    glClear(GL_COLOR_BUFFER_BIT); // Clear display window.

    for( size_t i = 0; i <= numObj; ++ i ) {

        if (list[numObj].t==1){

            glBegin(GL_LINE_LOOP);
            glVertex2i(list[i].x1, list[i].y1);
            glVertex2i(list[i].x1, list[i].y2);
            glVertex2i(list[i].x2, list[i].y2);
            glVertex2i(list[i].x2, list[i].y1);
            glEnd();
        }
    }
    glFlush();
}

用鼠标拖动OpenGL绘图矩形？

1 个答案: