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Clarification on SLAT/PVC conditioner implementation vs. paper Figure 2 #23

@nepfaff

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@nepfaff

Hi, thanks for releasing ReconViaGen. I’m studying the training code and had a question about the local per-view condition used for SLAT Flow.

In the paper, Section 3.2 and Figure 2 seem to describe the SLAT/PVC path as using a Condition Net similar to the SS/global path: random/learnable per-view tokens are updated by cross-attention blocks over VGGT features, producing per-view token lists T_k. Figure 2 also shows per-view cross-attention in SLAT Flow followed by a learned/weighted fusion.

In the released code, the SLAT conditioner appears to be simpler:

  • ModulatedSLATMultiViewCond in trellis/models/structured_latent_flow.py starts from DINO image_cond, not learned/random per-view query tokens.
  • It applies four Linear(ctx_channels -> channels) + ReLU blocks over concatenated VGGT features and the current condition.
  • I do not see self-attention or cross-attention blocks inside the SLAT conditioner, unlike the SS conditioner.
  • In trellis/modules/transformer/modulated.py, when the SLAT DiT receives a list of per-view conditions, it seems to average per-view cross-attention outputs with / len(context) rather than using a learned weighted fusion MLP as described in the paper.
  • In the v0.5 branch I noticed fuse_blocks are declared in ModulatedSLATMultiViewCond, but they do not appear to be used in forward.

Could you clarify whether this released implementation is the one used for the paper’s SLAT/PVC results? If so, was the simpler MLP-based SLAT conditioner chosen for stability, memory, or ease of training compared with the cross-attention Condition Net shown in the paper? Or is the paper diagram describing an earlier/internal variant?

I’m asking because the SS/global conditioner in code closely matches the paper, while the SLAT/PVC path looks architecturally different. Any explanation of the intended design tradeoff would be very helpful.

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