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helgehelge123andClaude Opus 5.5 90a248edad M12: Describe selections from SAM 3's semantic mask: sure inside, no lines between instances
Describe merged the detector's per-instance masks. Those stay near 0 even well inside what they
found: a sky came out about 87 % selected, a volleyball net about 70 %, a person about 94 %.
Two instances that touch both fade out where they meet, so a line showed between people standing
side by side.

- The detector's semantic head is now ported: semantic_projection over the pixel decoder, the
  transformers implementation's semantic_seg. It matches the reference to about 1e-3, like the
  instance masks. tools/sam3_reference.py writes it and the reference test checks it; older
  reference files still pass.
- Each instance found (score above the threshold, as before) takes the semantic logits where it
  is the strongest instance and near (above -4). The semantic mask is sure inside and runs on
  across the boundary between two instances. Far from every instance nothing changes, so
  Describe selects nothing it didn't find before.

On 16 prompts over three photos (a mountain landscape, two gym photos), the median coverage
inside each selection rises, e.g.:
- sky 0.87 -> 1.00
- mountains 0.81 -> 0.99
- net 0.71 -> 0.99
- floor 0.92 -> 1.00
- person 0.94 -> 0.99

Each selection gains 0 to 1.9 % of the photo at its soft rim and loses none.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-16 01:35:59 +02:00
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