For this purpose, we employ a lightweight visibility test to
estimate the expected unoccluded vertical extent of each potential
wall patch P. In our technique, an occlusion happens if the OBB of
a patch P and that of an occluder O overlap when seen from the
scan position from which they were taken. We construct the
infinite shadow volume [26] of each O by casting rays from the
scan position through the vertices of its OBB. We then compute the
intersection of this shadow volume with the plane induced
by P through its normal and the center of its OBB. Finally,
the projection of the shadow volume is tested for overlap with
the bounding rectangle of P (i.e., the projection of its OBB).
In practice, we scale each OBB by a factor of 1.05 to ensure
intersection between the shadow volume of O and the bounding
rectangle of a potentially occluded patch P. The process is
illustrated in Fig. 3. If an occlusion between P and O occurs, we
consider the vertical extent of the projection of O onto P and
merge it to the vertical extent of P itself. By repeating this check
for every O, we obtain the combined height h of P. We then prune
P from the candidate list based on the following condition:
hrð1ηÞ hrooms. Here η is a small number which we set to 0.05
and hrooms is the distance between the floor and the ceiling.
For this purpose, we employ a lightweight visibility test toestimate the expected unoccluded vertical extent of each potentialwall patch P. In our technique, an occlusion happens if the OBB ofa patch P and that of an occluder O overlap when seen from thescan position from which they were taken. We construct theinfinite shadow volume [26] of each O by casting rays from thescan position through the vertices of its OBB. We then compute theintersection of this shadow volume with the plane inducedby P through its normal and the center of its OBB. Finally,the projection of the shadow volume is tested for overlap withthe bounding rectangle of P (i.e., the projection of its OBB).In practice, we scale each OBB by a factor of 1.05 to ensureintersection between the shadow volume of O and the boundingrectangle of a potentially occluded patch P. The process isillustrated in Fig. 3. If an occlusion between P and O occurs, weconsider the vertical extent of the projection of O onto P andmerge it to the vertical extent of P itself. By repeating this checkfor every O, we obtain the combined height h of P. We then pruneP from the candidate list based on the following condition:hrð1ηÞ hrooms. Here η is a small number which we set to 0.05and hrooms is the distance between the floor and the ceiling.
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