Reflected-Scene Impostors for Realistic Reflections at Interactive Rates
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The sample-based
camera (SBC) is a method for rendering curved reflectors based on
projecting reflected vertices. The SBC is a set of BSP trees with simple cameras
at their leafs. When the reflector geometry is complex, the viewing volumes of
the simple cameras intersect and they cannot be efficiently separated by the BSP
tree, which leads to inefficient projection. In order to support complex
reflectors we developed a reflection rendering technique based on simplifying
the reflected scene, which is approximated with billboard and depth map
impostors. The intersection between a ray and a billboard is inexpensive. For
depth maps we developed an intersection algorithm that leverages epipolar
constraints to efficiently compute a quality approximation for the first
intersection with a ray. Like environment mapping, our technique does not pose
any restriction on the geometry of the reflectors, it supports dynamic scenes,
and it runs at interactive rates with the help of graphics hardware. Unlike
environment mapping, reflected-scene impostors produce realistic reflections by
correctly conveying the distance to the reflector surface and by providing
motion parallax. |
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Four inter-reflecting teapots, 40fps (left) and
reflection attenuation with distance and Fresnel effects, 66fps
(right). Both images were rendered with billboard
impostors. |
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Intersecting diffuse and reflective bunnies, 16fps. The image
was rendered with a depth map impostor.
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Reflectors distorted in real time. The images
were rendered with a billboard at refresh rate (left) and
a depth map impostor at 16fps (right). |
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Extreme distortions caused by concave
reflectors. Billboard (left) and depth image (right)
impostors handle extreme minification and magnification well.
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Illustration of morph from billboard to
environment mapping. The statues surrounding the teapot (left)
are part of the environment map. The billboard is highlighted
with purple. The reflection is continuous between the billboard
and the environment map (right). |
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