Perspective Shadow Maps Marc Stamminger REVESINRIA SophiaAntipolis France

Perspective Shadow Maps Marc Stamminger REVES/INRIA, Sophia-Antipolis, France now at: Bauhaus-Universität, Weimar, Germany George Drettakis REVES/INRIA, Sophia-Antipolis, France http: //www-sop. inria. fr/reves

shadow maps n Williams, Siggraph ‘ 78 – render scene from light source – shadowing by depth comparison

shadow map aliasing n prone to aliasing when zooming into shadow boundaries single shadow map pixel

shadow map aliasing n perspective aliasing parallel light aliased okay

shadow map aliasing perspective aliasing oversampled – smooth transition aliased n

shadow map aliasing n projection aliasing parallel light

shadow map aliasing projection aliasing oversampled – very local aliased n

previous work n Reeves et al. , Siggraph ’ 87: – “Percentage Closer Filtering” n Tadamura et al. , Visual Computer ’ 01 – “Plural Sunlight Depth Buffers” n Fernando et al. , Siggraph ’ 01: – “Adaptive Shadow Maps”

post-perspective world space perspective transformation

perspective shadow map standard shadow map n perspective shadow map image n

perspective shadow map standard shadow map oversampled n aliased n perspective shadow map

perspective shadow map in post-perspective space n just another shadow map projection n reduces perspective aliasing n regeneration per frame necessary n

light source transformation n parallel light becomes point light

post-perspective world space parallel light transformation

post-perspective world space point light transformation

best case: – parallel light in post-perspective space – no new perspective distortion post-perspective n world space discussion

non-optimal case: – point light close to frustum n worst case: – becomes uniform shadow map post-perspective n world space discussion

near plane selection n near plane as far as possible

near plane selection n automatic selection: reading back depth buffer

shadows from behind n virtually move camera backwards

shadow map window n geometric method to include all necessary objects – details in the paper

results

results n first implementation on an Xbox game developer kit courtesy of Thatcher Ulrich

conclusion n perspective shadow maps – shadow map in post-perspective space – just another shadow map matrix – non-uniform shadow map resolution – needs recomputation per frame – minimal overhead for dynamic scenes

acknowledgements Marie Curie Post-Doctoral Fellowship of the European Union n Bauhaus-Universität Weimar n Lutz Kettner (http: //www. cgal. org) n Frédo Durand n

thank you http: //www-sop. inria. fr/reves