This　paper　reports　on　a　visual　simulation　system　that　supports　GIS-based　realistic　modeling　and　real-time　rendering　of　forest　scenes.　Geometric　models　of　trees　are　automatically　generated　according　to　inventory　database　andpre-designed　template　models.　A　combined　image　and　geometry　representation　method　for　3D　tree　model　is　given　with　a　specific　level　of　detail　algorithm　for　ensuring　real-time　frame　rates.　We　have　tested　and　evaluated　the　system　in　applications　of　walkthrough　simulation　and　forest　fire　visualization.　©　2004　IEEE.