3D Photography: Outline Website Overview of 3D ... - Visgraf - Impa
3D Photography: Outline Website Overview of 3D ... - Visgraf - Impa
3D Photography: Outline Website Overview of 3D ... - Visgraf - Impa
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@ Luiz Velho - IMPA SIBGRAPI 2002<br />
Processing images<br />
Edge Detection<br />
• To recover coded information a pattern detection<br />
procedure has to be carried out on captured images.<br />
• The precision <strong>of</strong> pattern detection is crucial to the<br />
accuracy <strong>of</strong> resulting range data.<br />
• Shadow areas also have to be detected.<br />
• Stripes transitions produce<br />
edges on camera images.<br />
• Transitions can be detected<br />
with sub-pixel precision.<br />
• Projecting positive and<br />
negative slides is a robust<br />
way to recover edges.<br />
55<br />
@ Luiz Velho - IMPA SIBGRAPI 2002<br />
56<br />
Edge Coding<br />
Rusinkiewicz 4 frames graph<br />
01 11<br />
Frame 1 (column 1)<br />
Frame 2 (column 2)<br />
The graph edges are not oriented and<br />
correspond to the stripe transition code<br />
00<br />
10<br />
edge 00 → 01<br />
The maximal code<br />
results from an Eulerian<br />
path on graph.<br />
Obs.: 2 frames <strong>of</strong> Gray<br />
code gives us 4 stripes.<br />
In this case we have 10.<br />
@ Luiz Velho - IMPA SIBGRAPI 2002<br />
57<br />
@ Luiz Velho - IMPA SIBGRAPI 2002<br />
58<br />
4 frames stripe boundary code<br />
Ambiguity in decoding<br />
time<br />
one pixel over time<br />
one frame<br />
space<br />
• When using a binary base, ghost boundaries have to be allowed<br />
in order to obtain a connected graph.<br />
• The decoding step isn’t straightforward, due to the presence <strong>of</strong><br />
ghosts. A matching step have to be carried out.<br />
@ Luiz Velho - IMPA SIBGRAPI 2002<br />
59<br />
@ Luiz Velho - IMPA SIBGRAPI 2002<br />
60
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