simplify: Split quadrics update into a separate function #788
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Instead of updating quadrics as we are collapsing edges, we can update them in batch after all collapses are done. This makes the code cleaner since we do not need to replicate the collapse structure explicitly for both remap and quadric update, and also makes it ~5% faster on many large meshes - presumably due to better data locality during the update. The only subtle part here is vertex_quadrics update: we need to do this just once, and we *know* the primary vertex will have to move if any wedge moved, so we do that during the corresponding collapse. The target vertex may not have had any collapses to the primary vertex in case some vertex gets collapsed into a locked vertex. This change results in exactly identical results; in the future, this would result in a more careful handling of Complex collapses as our note about the attribute quadrics not requiring a merge was incorrect - even though the attributes might be similar, merging quadrics is still valuable to get area accumulation.
This way performEdgeCollapses no longer needs access to quadrics data, and when attributes are used and we need to compute distance error, the access to vertex quadrics is maximally local as we use them right after aggregation, which saves 1-2% on large meshes. For now we keep the optimization of not recomputing the distance error unless attributes are used; it makes the data flow slightly awkward and seems to have <1% performance impact but we can remove it later if it becomes more problematic.
The only reason why seam pair was computed separately was to reuse that computation between collapse and quadric updates as it is fragile; now that we have split quadric updates completely, sx is only used for collapse update and it's thus better and cheaper to process inline.
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Instead of updating quadrics as we are collapsing edges, we can update
them in batch after all collapses are done. This makes the code cleaner
since we do not need to replicate the collapse structure explicitly for
both remap and quadric update, and also makes it ~5-7% faster on large
meshes - presumably due to better data locality during the update.
The only subtle part here is vertex_quadrics update: we need to do this
just once, and we know the primary vertex will have to move if any
wedge moved, so we do that during the corresponding collapse. The
target vertex may not have had any collapses to the primary vertex in
case some vertex gets collapsed into a locked vertex.
This change results in exactly identical output; in the future, this
would result in a more careful handling of Complex collapses as our note
about the attribute quadrics not requiring a merge was incorrect - even
though the attributes might be similar, merging quadrics is still
valuable to get area accumulation.
This contribution is sponsored by Valve.