5
Shadow Maps
• Advantages– Only one additional
render pass– Very easy to use
• Disadvantages– Aliasing problems– Resolution restricted to
available memory– Requires a user-set bias.
6
Perspective Shadow Maps
• Better utilizes available samples by warping depth map
• Find the volume that can contribute shadows to the view
• Fit light frustum to the volume in camera’s post-perspective space
• Render depth map in camera’s post-perspective space.
Perspective
12
Shadow Volumes
0
1 1
2 21
0
• Extrude shadow frusta from occluder edges to infinity
• Count crossings from eye to a point: – Front faces: +1– Back faces: -1
• If crossings > 0 then point is in shadow
13
Shadow Volumes
• Advantages:– No aliasing. Crisp
shadow edges– Can be done on
commodity hardware– Light need not be
restricted to a frustum
14
Shadow Volumes
• Advantages:– No aliasing. Crisp
shadow edges– Can be done on
commodity hardware– Light need not be
restricted to a frustum
• Disadvantages:– Needs CPU– FILL!!! 4.8 billion pixels per
second / (1024 * 1024 ) 4600 screen fills per second