c++ - 无法正确定义一个 QUAD

Question

我想要一个矩形立方体。一堵墙的脸朝反面所以我看不到粉红色。这是立方体好的一面:

在立方体的背面，墙的背面是灰色的:

这是代码:

glBegin(GL_QUADS);
    //floor
    glMaterialfv(GL_FRONT, GL_DIFFUSE, floor_diffuse);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);

    //roof
    glMaterialfv(GL_FRONT, GL_DIFFUSE, roof_diffuse);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);      
    //walls
    glMaterialfv(GL_FRONT, GL_DIFFUSE, walls_diffuse);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);

    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);

    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);     

    //BAD WALL
    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);

    glEnd();

我已经尝试了所有组合(逆时针)，但结果仍然相同。有任何想法吗？

Answer 1

我相信您错误地识别了您的墙。您创建的第一个 (X = - floor_size_x/2)、第三个 (Z = - floor_size_z/2) 和第四个 (Z = floor_size_z/2) 都是顺时针指定的，而第二个 (X = floor_size_x/2) 是逆时针指定的。我猜这实际上是错误的。