??�BSP Trees and Polygon�???"RENDER-PORTAL-ENGINE&am

GH

�Portal Rendering�???27?

?????�????????�??????

RENDER-PORTAL-ENGINE (Sector, ViewFrustum)
1 for each polygon P1 in Sector
2     if (P1 is a portal and INSIDE-FRUSTUM (ViewFrustum, P1))
3        NewFrustum = CLIP-FRUSTUM (ViewFrustum, P1)
4        NewSector = get the sector that is connected with the current sector through portal P1
5        RENDER-PORTAL-ENGINE (NewSector, NewFrustum)
6     else if (P1 has not been drawn yet)
7        draw P1
8 return

???????Viewer??Sector??????????????(ViewFrustum)????????????? if ???????

if (P1 is a portal and INSIDE-FRUSTUM (ViewFrustum, P1)) {...}
else if (P1 has not been drawn yet) {...}

???????Sector??????????????????????????????

?????????????

RENDER-PORTAL-ENGINE (Sector, ViewFrustum)
1 for each polygon P1 in Sector
2     if (INSIDE-FRUSTUM (ViewFrustum, P1))
3        if (P1 is a portal)
4             NewFrustum = CLIP-FRUSTUM (ViewFrustum, P1)
5             NewSector = get the sector that is connected with the current sector through portal P1
6        RENDER-PORTAL-ENGINE (NewSector, NewFrustum)
7          else if (P1 has not been drawn yet)
8                 draw P1
9 return

???????????????

(??"Binary Space Partioning Trees and Polygon"?????????????????????????????????????

secondage

a.  if (P1 is a portal and INSIDE-FRUSTUM (ViewFrustum, P1))

b.    if (INSIDE-FRUSTUM (ViewFrustum, P1))
        if (P1 is a portal)

a ??b ?????????????????????????????????

GH

???????polygon???portal,???????????????
????????polygon??portal,???????? (P1 has not been drawn yet) ?????portal?polygon?????????????????????????????????

??????????polygon?portal,????????????????3?4?5?????????????? 7 draw p1 !!!! ??portal??????? draw ?

??????????:

1 for each polygon P1 in Sector
     {
2     if (P1 is a portal and INSIDE-FRUSTUM (ViewFrustum, P1))
          {
3         NewFrustum = CLIP-FRUSTUM (ViewFrustum, P1)
4         NewSector = get the sector that is connected with the current sector through portal P1
5          RENDER-PORTAL-ENGINE (NewSector, NewFrustum)
          }
6     else if (P1 has not been drawn yet)
7              { draw P1 }
      }
8 return

secondage

?????????�and �???c????&&??????????
???????????????else?

??portol??????

????portal?????????portal->draw??????????????portal??????????debug