- glPushMatrix();
- glLoadIdentity();
-
- double clip[4];
- clip[0] = 1;
- clip[1] = 0;
- clip[2] = x-size;
- clip[3] = 0;
- glClipPlane(GL_CLIP_PLANE0, clip);
- glEnable(GL_CLIP_PLANE0);
-
- clip[0] = -1;
- clip[2] = -(x+size);
- glClipPlane(GL_CLIP_PLANE1, clip);
- glEnable(GL_CLIP_PLANE1);
-
- clip[0] = 0;
- clip[1] = 1;
- clip[2] = y-size;
- glClipPlane(GL_CLIP_PLANE2, clip);
- glEnable(GL_CLIP_PLANE2);
-
- clip[1] = -1;
- clip[2] = -(y+size);
- glClipPlane(GL_CLIP_PLANE3, clip);
- glEnable(GL_CLIP_PLANE3);