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Xorand

Some questions about shadow volume

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Practical and Robust Stenciled Shadow Volumes for Hardware-Accelerated Rendering, by Cass Everitt and Mark J Kilgard. It is my reference to cast a shadow(zfail with capped,infinite shadow volumes). There are some words from it:"Unless specially handled, such polygonal models must be closed (2-mainfold) and be free of non-planar polygons." Can anyone teach me what "specially handled" is or what I should do to fix non-closed model. Thank you very much.

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to non-closed models:

for shadow volumes, you must determine the silhouette of the object. if the object is not closed, the silhouette of the object may not be found by the algorithm you use. this can result in shadowing artifacts.

i think somethink similar applies to models with non-planar polygons.

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Thanks for your reply. I draw the shadowed quads if there is no neighbouring face, or the neighbouring face is not visible, at the visible edge. The result is correct in zpass. But it is useless in zfail with capped. I think it is because of the cap. I try to fix it. But I don't know how to fix it without fixing non-closed model at last. Can anyone teach me there is other way to fix it? Thank you.


[edited by - Xorand on April 21, 2003 9:03:58 AM]

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you could draw the non visible faces in CCW/ or CW order in order to make them visible
thats propably the easiest solution

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Sorry. I am a little confused about what you say. Can you tell me where I should draw these non visible faces? One pass,two pass, or not in stencil buffer? Thank you very much.

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