| | Original (SAM 3D body) | Ours (Fast SAM 3D body) |
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| Input: Image I Output: MHR parameters θ^ (+ SMPL parameters Θ^smpl for deployment) |
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| Detect | bi←Detect(I) body boxes only | bibL,bR←Detect(I) body + hand boxes |
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| Encode | Fbody←Enc(Crop(I,bi)) backbone #1 | [Fbody,FL,FR] ←Enc(GPUCrop(I,bi,bL,bR)) backbone × 1, batched |
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| Body | θ^←BodyDec(Fbody) | θ^←BodyDec(Fbody) |
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| Hands | bL,bR←ProjectWrist(θ^) wait for body dec. FL←Enc(CPUCrop(I,bL)) backbone #2 FR←Enc(CPUCrop(I,bR)) backbone #3 θ^L←HandDec(FL) θ^R←HandDec(FR) sequential, 2 passes | θ^L,θ^R←HandDec([FL,FR]) batched, 1 pass (features from Encode stage) |
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| Merge | θ^←Merge(θ^,θ^L,θ^R) | θ^←Merge(θ^,θ^L,θ^R) |
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