Fixes #11

Problem

When both seq_init=True and cross_view=True are enabled, the filtering condition becomes mathematically impossible to satisfy:

• seq_init=True sets r=1
• cross_view=True sets c=1
• Condition: abs(ii-jj) > 1 AND abs(ii-jj) <= 1 is impossible

This results in zero edges being added to the factor graph, causing initialization to fail.

Solution

Changed c = 1 if self.cross_view else 0 to c = -1 if self.cross_view else 0

This allows:

• Cross-view connections at same timestamp (ii == jj)
• Neighborhood connections within radius r

Testing

• Previously failing 360-degree video now processes successfully
• No regression on existing functionality

Credit

Thanks to @heiwang1997 for the elegant solution suggestion!